Brachial- and lumbosacral plexus tumours zone system for surgery brain and spine nerve edition

Abstract

Introduction

Operating on plexus related neoplasia involves a higher risk for morbidity and functional deterioration. For neck-and intrapelvic plexus tumours (tu) a variety of approaches exist, with fluent transition to standard spine, abdominal and thoracic surgery. We described a systematic approach selection for complex multi compartmental lumbosacral plexus tumours before. Based on this decision pathway we now suggest a unifying classification system, applicable for both brachial- and lumbosacral plexus.

Objective

To introduce a unifying zone system for brachial- and lumbosacral plexus to ease adequate approach selection for simple and complex nerve associated plexus tumours. The system further refines our approach selection process for these patients.

Method

Based on MRI, localisation, tumour boundaries and their correlation to landmarks define core zones that facilitate the choice of one or the combination of different appropriate approach/es: in brachial plexus tumour BP Zone I-IV with spinal (Spi), foraminal (For), lateral thoracic wall (Ltw) extension; in lumbosacral tumour LSP Zone I-III with spinal (Spi), foraminal (For), femoral (Fem), Sci (sciatic) extension.

Result

The system works to easily classify plexus tumours in groups and suggests appropriate approach choices, even involving combinations of surgical accesses not described previously.

Conclusion

We propose the “Zone plus extension Plexus tu classification system” derived from tumour imaging to classify brachial- and lumbosacral plexus tumours prior to surgery. The necessary decision making inherently suggests approach combinations for tu removal. The classification thus aids to secure adequate exposure to prevent untoward surgical compromises.

Highlights

• •Proposal of a simple categorisation system that follows the same systematic for brachial and lumbosacral plexus tumours.
• •Zone system with extensions defines localisation and thus necessary approach choice.
• •Case based examples with patient positioning and skin incisions are given.
• •Application of system aids in preoperative surgical planning.

Abbreviations

ANNUBP =

Atypical neurofibromatous neoplasm of uncertain biological poptential

BMRC =

British Medical Research Council

BP =

brachial plexus

Ca =

Carcinoma

Fem =

femoral

For =

foraminal

Il =

iliopsoas

LSP =

lumbosacral plexus

Ltw =

lateral thoracic wall

MMNST =

Malignant melanotic nerve sheath tumour

MPNST =

Malignant Peripheral Nerve Sheath Tumour

MRI =

Magnetic Resonance Imaging

PNST =

Peripheral Nerve Sheath Tumour

Prom =

promontory

Scap =

subscapular

Sci =

sciatic

Spi =

spinal

Tu =

tumour

VBR =

vertebral body replacement

1. Intro

Plexus associated tumour surgery necessitates the use of multiple different surgical approaches (Häckel et al., 2023; Landriel et al., 2024). In complex cases these are combined to improve resection security via enlarged exposure in single or staged surgery (Spinner et al., 2006; Heinen et al., 2020). To date no consensus has been reached for the optimal surgical strategy of neither brachial- nor lumbosacral plexus tumours (Lubelski et al., 2022). This especially applies regarding preoperative biopsy (Guedes et al., 2024) (Perez-Roman et al., 2020). In case of neural sheath pathology (PNST) neural deficit and pain is feared as a potential consequence (Martin et al., 2022; Al-Mistarehi et al., 2024). Accordingly, tumour type frequently is not known prior to surgery, which significantly affects the surgical goal, approach and technique (microsurgical interfascicular dissection under neuromonitoring vs extirpation vs resection).

2. Method

We describe our plexus tumour categorisation/classification systematic, one for the brachial plexus (BP) and one for the lumbosacral plexus (LSP) to aid presurgical decision making on approach choice and use for potential selection of approach combinations. The BP- and LSP-zone systems are based on topographical relation of tumour to simple, but approach decisive imaging landmarks. The defined zones and their modular extensions are related to apt approaches. For tumours of large expansion covering two or more zones, related approaches can be combined for optimal exposure.

3. Results - plexus tumour categorisation systematics

3.1. Brachial plexus tumour characteristics

Brachial plexus tumours (BP tu) reportedly are 69.5 % supraclavicular and 30.5 % infraclavicular (Shekouhi and Chim, 2023): The most common locations within the plexus are the trunks, followed by roots, cords, and terminal branches. Schwannomas have a predilection for trunks and roots in the supraclavicular plexus. Neurofibromas have lower gross total resection rates than Schwannomas. Multiple entities can be encountered, which are either nerve sheath or non-nerve sheath associated, primary or secondary neoplasia (Table 1).

Table 1.

Possible entities of brachial plexus tumours (Desai, 2017)^, (Pisapia et al., 2023) (Lahr, 2004) (Jack et al., 2021) (selection).

Brachial plexus tumours
Nerve sheath tumours (for current classification changes see (Meyer and Billings, 2020; Belakhoua and Rodriguez, 2021)) Schwannoma benign/malignant, neurofibroma benign/malignant, Hybrid tumour (Lang et al., 2012), perineurioma, malignant Triton tumour other name/is a type of soft tissue sarcoma/may arise from preexisting nerve tissue tumour in NF 1 Patients, benign Triton tumour/neuromuscular choristoma, Malignant melanotic nerve sheath tumour/MMNST (mediastinum, spinal nerve roots, subset associated with carney complex/syndrome), Atypical neurofibromatous neoplasm of uncertain biological poptential/ANNUBP
Non-nerve sheath tumours Soft tissue sarcoma (alveolar, spindle cell, synovial, fibrosarcoma, liposarcoma, leiomyosarcoma, Triton tu in non-NF 1) osteosarcoma, primary extraskelettal Ewing sarcoma, malignant fibrotic histiocytoma (also a sarcoma type), hemangiopericytoma, Aggressive fibromatosis/desmoid, Ganglioneuroma, Meningioma, Osteochondroma, Metastasis: Ca breast, Melanoma, Ca lung, Renal Ca, Pancoast Tu = non-small cell carcinoma of the lung at lung apex Lymphoma

Depending on growth and size they extend into adjoining spaces or infest along the elements and nerves from the plexus. Malignant brachial plexus sheath tumours are rare and with a 5-year survival between 15 % and 50 % have poor overall survival rates (Farid et al., 2014) (Stucky et al., 2011). In unexperienced hands patients are prone to deficits after surgery. A 3 % mortality rate in surgical treatment of brachial plexus tumours is reported in a metanalysis of 687 patients with 693 tumours operated at experienced centres (90.8 % benign, 9.2 % malignant, mean tumour size of 5.4 ± 3.1 cm) (Shekouhi and Chim, 2023).

3.2. BP tumour surgical planning

Brachial Plexus tumours grow along and into different compartments of the neck, spine, thoracic aperture, axilla, chest wall and dorsum, as well as subscapular. Their microsurgical removal is challenging, even in more confined locations like the supraclavicular neck. In order to plan and custom tailor the surgical approach to the primary location and extension of the tumour, it is crucial to understand its full architecture by careful preoperative analysis of imaging in three planes. Surgical objective and radicality (decompression, biopsy, excision, extirpation) as well as pathology (benign vs malignant, correlated response rates for chemo-, immune, radiation-therapy) dictate exposure needed.

3.3. Definition of BP tumour zones and extensions

In dependence on primary localisation of the tumour and potential extensions into other compartments, or anatomical regions we define four main brachial plexus tumour (BP tu) zones with accordingly added extensions. By this simple categorisation the necessary approach, or approach combinations can be delineated and help preoperative planning of surgery.

Zones I, II, III, IV with anterior, lateral and dorsal spinal approach extensions (Table 2, Table 3; Fig. 1):

Table 2.

Definition of BP Tumour Zones I to IV based on the main location of the tumour bulk and correlation to a suitable approach entry port and incision.

BP-Zone	I	II	III	IV
Main tu Location	Supraclavicular to retroclavicular	Infraclavicular to retroclavicular	Axillary to infraclavicular	Cervical and thoracic midline
Surgical entry port	Supraclavicular, transverse or T-ed	Infraclavicular, Oblique, vertical or T-ed incision	Medial proximal upper arm, horizontal incision in bicipital sulcus, or vertical incision along lateral pectoral fold	Supra- and infraclavicular entry, via medially placed T-ed incision can reach up to T1, if more extensive dissection needed (e.g. vertebral body replacement) ± lower reach to T2/3 level a manubriotomy to partial sternotomy is needed with vertical to L-shaped skin incision, or a more classic “trap-door“ thoracosternotomy approach

Table 3.

If BP tumour extends past the assigned zone into the periphery or spine an Extension acronym is added to the main classification zone – BP tu Zone I-IV ext (Spi, For, Scap, Ltw).

Surgical approach extensions for all BP Zones
Extension akronym	Spi	For	Scap	Ltw
description	Intraspinal dorsal, lateral, anterior	Foraminal	Subscapular	Lateral thoracic wall

Fig. 1.

Depiction of defined brachial plexus tumour zones on the left with possible spinal and thoracic tumour extensions on the right and corresponding approach options in the middle.

Dependent on primary location (zone), size of the brachial plexus tumour (one or several zones covered), topographical relations, tumour extension and primary objective of surgery (decompression, biopsy, removal) the approach is chosen (one or several approach ports, bone removal or transection). In more complex cases tumour covers more than one zone and extends to neural foramina, abuts the spine, grows intraspinal, to the scapula, or lateral thoracic wall. In these cases, approach incisions to reach for the respective zones and extensions are combined.

As referenced above, for PNST most of the times a supraclavicular (Zone I) or an infraclavicular (Zone II) location and thus approach is apt for adequate exposure. For Zone I, a horizontal supraclavicular incision is used, for Zone II an oblique or vertical infraclavicular one. For a sizeable Zone I and II tu we favour a T-ed incision from supra-to infraclavicular, as introduced by Rolfe Birch and termed by him Fiolle-Delmas approach (Birch, 2011). Rarely tumours are retroclavicularly centred and are placed with their tumour bulk equator in between Zone I and II in a way that save fascicle separation is not feasible with upward or downward clavicle retraction by a looped string. These can than potentially be considered for claviculotomy. Claviculotomy leads to instant lateral and downward shift of the shoulder. This immediately opens a several centimetre wide gap between the clavicle ends, which greatly enlarges view and the surgical field. The very rare necessity needs to be weighed against the effort of clavicular plate reconstruction. Some tumours will sit primarily in the axilla with an infraclavicular component (Zone III) as for example metastasis and lymphoma. Incisions used are behind and parallel to the anterior axillary fold and horizontally along the bicipital sulcus in the most proximal medial upper arm.

On rare occasions the mass sits more central in or closer to the cervicothoracic midline (Zone IV). Especially cervicothoracic bone metastasis, or primary bone tumour infesting the brachial plexus at thoracic levels one to three are hard to reach from a more lateral approach. Even more so if substantial bone resection and vertebral body replacement is involved. These are cases that might need a manubriotomy or partial sternotomy, if not even “trap-door“thoracotomy. If the vertebral spine as such is tumour free and intact the lower plexus elements up to a foraminal and intraspinal level can be reached via a dorsal subscapular approach (Dubuisson et al., 1993; Crutcher et al., 2017), or its variations (Aghayev, 2023).

The various approaches to the brachial plexus and their respective reach are summarized in Table 4.

Table 4.

Potential reach of various approaches used for brachial plexus tumours.

Tumour location ⇩	Approaches ⇨ Supraclavicular horizontal	Infraclavicular vertical to oblique	Sub- to transaxillary	Transforaminal	Dorsal spinal	Anterolateral (“Whitesides”)	Fiolle-Delmas-Birch = T-incision	Dorsal subscapular and lat subscapular
Supraclavicular	x						x
Retroclavicular	x	x					x
Infraclavicular		x	x				x
Axillary		x	x				(x)
Intraforaminal	x			x	x	x	x	x
Intraspinal				x	x	x	x	x
Thoracic		x	x				x	x
Subscapular								x
Plexus dorsal aspect & lower rots							(x)	x

3.4. Case examples for application of BP zone system

BP Z-I, Spi, For extension ( Fig. 2 )

Fig. 2.

BP Zone-I tumour with foraminal (For) and spinal (Spi) extension. C6 BP PNST extending over neural foramen to intraspinal with severe myelon compression. Clinically pressure and pain, severe gait disturbance, severe C5 and 6 palsy BMRC 2 for deltoid and biceps in athlete. Pre-operative MRI imaging with C5/6 supraclavicular, homogenous enhancing mass with arrow pointing towards tumour on sagittal (A) and axial with intraspinal -(B) and foraminal mass (C). Combination of dorsal median C 5/6- (D, vertical dotted line for intraspinal and intraforaminal part) with supraclavicular plexus approach for C6 an plexus (D, horizontal dotted line) was choosen in a single stage surgery with semi-sitting position allowing to reach pathology from a posterior and lateral surgeon position. Post-operative sagittal (E) and axial (F) MRI demonstrate tumour exstirpation (white arrows) and submuscular dissection path along muscles with low density signal.

C6 BP PNST (Schwannoma) extending over neural foramen to intraspinal with severe myelon compression. Clinically pressure and pain, gait disturbance, severe C5 and 6 palsy BMRC 2 for deltoid and biceps (only partially compensated by other muscles).

Tu Location: BP-Zone I with spinal (Spi) and foraminal (For) extension along C6 root.

Surgical approach: Two separate entry ports with transverse incision at neck for intraplexal tumour part plus dorsal vertical incision for extended intraspinal to foraminal tumor part.

BP Z-I & II ( Fig. 3 )

Fig. 3.

BP Zone-I & II tumour. Middle trunk BP PNST with retroclavicular tumor bulk, on right side. Clinically incidental finding b/o imaging due to habitual shoulder luxation and associated pain episodes; after extramural biopsy increased pain and some weakness of right UE. On exam considerable pain to dorsolateral arm & hand/D3, shoulder abduction/anteversion limited to 30°, positive Tinel's sign, deltoid, triceps, supraspinatus BMRC 4. Pre-operative MRI imaging on coronal view (A) demonstrating fusiform tumour (arrows in A and B) of brachial plexus with inhomogenous signal and along tumour trajectory view (B). Tumour positioned behind clavicle (B, asterisk). Patient positioned supine and tumour approached via T-incision (C) with supraclavicular horizontal component. Tumor exposed (D, white arrow) via clavicle transection (asterisk marking lateral part of clavicle) enabling, fascicle sparing exstirpation of PNST originating from posterior division of middle trunk. Post-operative MRI (E) after complete removal with typical fusiform broadened plexus signal after complete removal (E, arrow) and X-Ray of plated clavicle (F).

Patient with habitual right shoulder luxation at rest. Since last repositioning persistent shoulder pain, therefore MRI imaging with detection of a retroclavicular mass of up to 7 cm compatible with BP PNST. Retroclavicular tumour equator with partially lobulated appearance and considerable supra- and infraclavicular parts. Prior, extramural tumour biopsy confirmed schwannoma and resulted in increased and new onset pain as well as algogenic weakness of upper arm. On examination restricted passive shoulder abduction to 30° with then triggerable pain. Positive Tinel's sign on deep supra- and infraclavicular tumour palpation. Pain radiating from clavicula to dorso-lateral upper- and forearm to middle finger. No circumscribed hypesthesia, triceps weakness BMRC 4 attributed to pain. Tumour removed via T incision to expose supra- and infraclavicular space; on exploration sling clavicle retraction not felt to generate enough exposure for intrafascicular tumour dissection, therefore clavicle transection with later plate reconstruction. Tumour origin division of middle trunk.

BP Z-III, potential Ltw extension ( Fig. 4 )

Fig. 4.

BP Zone-III tumour approach. Status post previous Plexus surgery 10 months before for left BP Zone-I & II MPNST via supra-infraclavicular T-incision. Confirmed high-grade rhabdomyosarcomatous bp tumour with small-cell differentiation; neoadjuvant immune- and radiotherapy. New onset left axillary growth in question extending to lateral chest wall. On pre-operative coronal (A) and axial (B) MRI unclear if imaging signal changes (A, B arrows) represent progression or post-radiogenic changes. Patient clinically impaired, but can abduct shoulder and has limited left hand function with painful paresthesias. Surgery to biopsy and remove potential growth to answer if next immunotherapeutic cycle were potentially indicated. Patient is positioned supine with arm abducted on flexible armboard, healed T-incision from previous surgery for BP Zone I & II tumor marked (C, dotted line). Current transaxillary approach (D) to plexus and lateral thoracic wall prepared with lateral pectoral incision marked (D, dotted line). For potential approach extension transpectoral old approach part was also draped. Postoperative MRI (E) demonstrates plexus and intact thoracic wall with still enhancing FDG-PET signal above left thoracic wall (F). Pathology identified post-radiogenic changes without evidence of new tumour expansion.

Patient status post previous surgeries for MPNST, then high-grade rhabdomyosarcomatous supra- and infraclavicular left brachial plexus tumour with small-cell differentiation previously operated via T incision. Now question of tumour progress vs. post-radiogenic changes of infraclavicular to axillary plexus extending to thoracic wall at second and third rib. Question of further additional cycle of offline chemotherapy dependant on surgical result (previous cycles were incriminating to patient). Clinically impaired but with possible and improved shoulder abduction and hand function since last tumour removal. Painful paresthesias to left fingers D 1-3, radial forearm and lateral proximal upper arm. On imaging suspicious mass limited to axilla and thoracic wall, correlating to a BP zone-III mass with lateral thoracic wall (Ltw) extension. Prepared for axillary entry port via lateral pectoral incision and potential lateral thoracic wall extension if needed for extended rib and thoracic wall resection in dependence on intraoperative pathology result.

On surgery tissue sparing reexploration of left brachial plexus via lateral axillary entry port reaching to lateral thoracic sufficed. Resection and biopsy from lateral thoracic wall at 2nd and 3rd rib and from infested lateral and posterior cord confirmed radiation induced changes. Surgery was completed by direct placement of intermittent „pain-catheter“connected to on-demand device.

BP Z-IV ( Fig. 5 )

Fig. 5.

BP Zone-IV tumor. Recurrrent renal cell cancer metastasis of vertebral bodies C7 to T2 with bilateral plexus infestation C8 and T1. After prior tumor removal with T1 vertebral body replacement and dorsal instrumentation there was new onset of local and bilateral radicular C8/T1 pain, progressive loss of hand & finger function right > left. Pre-operative MRI acknowledged recurrent tumour from C6 to T2 vertebral body bracketed between pedicle screws on sagittal (A) with tumour expanding to soft tissues also encasing C8/T1 roots and reaching esophagus on axial (B). Patient was positioned supine, and an inverted hockey-stick incision marked on right neck and midline over sternum (C). Depicted is anterior surgical approach from right lateral neck to sternal midline with partial sternotomy to intercostal space 4/5 for C8/T1 to myelon exposure (D) to enable 3.5 level anterior vertebral body replacement following staged dorsal recurrent tumour removal with pedicle screw re-instrumentation (not depicted). Post-operative CT-scan shows positioning of vertebral body replacement (VBR) and dorsal instrumentation in 3 D reconstruction (E) and on axial removed bone with centred VBR (F).

Recurrent renal cell cancer metastasis of vertebral bodies C7 to T2 with bilateral plexus infestation C8 and T1after initial T1 anterior vertebral body replacement and dorsal instrumentation. Clinically local and C8/T1 radiating pain bilaterally, progressive loss of hand and finger function right > left.

Surgical approach: Tumour and bone removal via lateral neck and midline approach with partial sternotomy for C8/T1for myelon exposure and 3.5 level vertebral body replacement (anterior midline), with prior dorsal instrumentation.

3.5. Lumbosacral plexus tumours, entities & characteristics

Lumbosacral plexus (LSP) tumours are located in the retroperitoneal space and depending on growth pattern and size extend into or infest adjoining spaces along the elements and nerves from the lumbosacral plexus (Luca et al., 2020). Malignant retroperitoneal tumours have poor survival rates and are prone to severe deficits after surgery. Reported are a 22% complication rate with substantial blood loss, urinary retention, reoperation due to surgery related complications in 14%, and a 4% mortality rate in 500 retroperitoneal soft tissue sarcomas.

3.6. LSP tumour frequency

Nerve tumour of retroperitoneal space is rare (Heinen et al., 2020) (Swallow et al., 2021) (Dafford et al., 2007)^, (Soldozy et al., 2023): Benign schwannoma 0.7-2.7%, retroperitoneal sarcoma 0.5 to 1 new cases per 100.000 inhabitants per year. One third of all retroperitoneal tumours are reported as sarcomas. Within the group of retroperitoneal sarcomas are 40 % dedifferentiated liposarcoma, 24 % well-differentiated liposarcoma, 20 % Leiomyosarcoma, 5 % solitary fibrous tumour and 3% malignant peripheral nerve sheath tumours (Memorial Sloan-Kettering Cancer Centre and Transatlantic Australasian Retroperitoneal Sarcoma Working Group summarized data of n = 2617 cases) (Swallow et al., 2021). A 32.8-month survival rate in 35 patients with limb preserving and limb amputation hemipelvectomy is reported in malignancy.

LSP tumour frequency in lumbosacral Plexus MRI (Rahmani et al., 2025):

A recent evaluation of 25 years of Yale's School of Medicine MRI data of lumbosacral plexus imaging (2000-2024, 1541-bed facility) for clinical symptoms or concerns revealed a LSP MRI rate of 0.0024% of all MRIs for that period (n = 233/968,077) with a 29 % identification rate of abnormalities (n = 67/233). Most frequent findings were nerve sheath tumours (n = 12, 5.2 %), other primary neoplasia or metastases (n = 15, 6.4 %) or other non-neoplastic compressive neuropathies (n = 11, 4.6 %). Less common were trauma (n = 5, 2.1 %) and infectious/inflammatory (n = 6, 2.6 %).

Imaging protocol was sagittal T2-weighted turbo spin echo (TSE) for spine alignment and disc, coronal T1-weighted TSE, for anatomical delineation of the plexus, coronal short tau inversion recovery (STIR) for edema, inflammation, or infiltrative changes, high-resolution coronal 3D T2-weighted SPACE isotropic multiplanar reconstruction to allow for improved depiction of plexus anatomy, and in select cases DTI 3D DW-PSIF to enhance nerve tract visualization and evaluate plexus microarchitecture.

3.7. LSP tumour types

• •Primary lesions: mesenchymal tumours (including sarcoma and neurogenic tumour) account for approximately half of all. Liposarcomas and leiomyosarcomas represent approximately 80 % of all adult retroperitoneal sarcomas. Parasympathetic tumours, extragonadal germ cell tumour, lymphoid tumours, cystic vestigial tumours, solitary fibrous tumours or desmoid, PEComas, deep angiomyxomas (infra-peritoneal), lymphangioma, and rarely haemangioma
• •Secondary lesions: metastatic carcinoma, adenopathy, lymphoma
• •Classification: fatty tumours, smooth muscle tumours, fibroblastic and myofibroblastic tumours, striated muscle tumours, vascular tumours, nerve tumours, extraskeletal osseous and cartilaginous tumours, uncertain tumour differentiation, unclassified/undifferentiated sarcomas (rare in retroperitoneum).

3.8. Definition of LSP tumour zones I-III and extensions

Zone categorisation focusses on topographical relation to promontory and psoas muscle on MRI imaging (Table 5 and Fig. 6). On sagittal views main tumour mass is either above (zone I) or below promontory (zones II and III). This has implications on risk to injure genitourinary tract, great vessels, hypogastric plexus. Below promontory main mass can be on or below psoas, or lateral to it (zone II). This implies less surgical risk, and accessibility for antero-lateral retroperitoneal approach, avoiding more invasive transperitoneal approach with intestinal mobilisation. Any mass below promontory and medial to psoas with or without major central part bears a higher surgical risk (zone III) regarding injury for genitourinary tract, iliac arteries or veins, and bladder. Prior surgery might necessitate transperitoneal approaches despite zone II categorisation. Major tumour extensions (Table 6 and Fig. 7) from zone category are classified as spinal (Spi), foraminal (For), sciatic infrapiriform (Sci) and femoral subinguinal or along obturator nerve (Fem). The promontory relation and tumour extension together determine to a major part the necessary approach combination for adequate exposure of the LSP tumor (Fig. 8).

Table 5.

Definition of LSP tu Zones I, II, III and recommended entry ports for assigned approach.

LSP-Zone	I	II	III
Main tu location	Above promontory, within psoas limits	Below promontory, lateral, or on/below psoas	Below promontory, central or medial to psoas
Surgical entry port, approach	Lateral to anterior abdominal (flank), retroperitoneal	Lateral-to anterior abdominal, retroperitoneal to transperitoneal	Midline abdominal, transperitoneal

Fig. 6.

LSP Zones I, II and III. The zones describe the main tumour location with respect to promontory (I above, II and III below) and psoas muscle (I lateral or centred on, III medial to psoas and centred). Reproduced and modified from (Heinen et al., 2020), with kind permission granted to Thomas Kretschmer from Wolters Kluwer.

Table 6.

If LSP tumour extends past the assigned zone into the periphery or spine an Extension acronym is added to the main classification zone – LSP tu Zone I-III Ext (Spi, For, Sci, Fem).

Surgical extensions for all LSP Zones
Extension acronym	Spi	For	Sci	Fem
Description approach	Intraspinal tu growth dorsal, lateral, anterior	Foraminal tu growth dorsal, lateral, anterior	Sciatic nerve route growth dorsal trans- or subgluteal to infrapiriform	Femoral nerve route growth anterior infrainguinal or obturatorial route

Fig. 7.

Tumor extensions along anatomical routes to spine or along sciatic nerve. Yellow arrows depict dorsal or lateral approaches which can be combined with anterior main approach. Reproduced and modified from (Heinen et al., 2020) with kind permission granted to Thomas Kretschmer from Wolters Kluwer.

Fig. 8.

Decision pathway for choosing approach combinations to expose and microsurgically operate on LSP tumours. Reproduced and supplemented from (Kretschmer and Heinen, 2025), with kind permission from Springer.

3.9. Case examples for application of LSP zone system

LSP Tu Zone I ( Fig. 9 )

Fig. 9.

LSP Zone-I tumour. Incidental finding following work-up for recurrent lumbar pain with history of testicular carcinoma; on exam no clear radicular pain, no sensorimotor deficits. On pre-operative imaging tumour on right L 5 root (A, coronal view, arrow), above promontory, sub psoas (B, sagittal view arrow) without intraforaminal extension. Surgical approach via navigated lateral abdominal incision with patient supine for retroperitoneal approach (C, asterisk in cranial direction), microscopic view of tumour with psoas displaced lateral by fixed retraction (D, tumour encircled, nerve in vessel loop, asterisk in cranial direction). On post-operative MRI L5 root tumour free on coronal- (E, middle root of three) and sagittal view. Abbreviations: prom = promontory; Il = iliopsoas.

Due to recurrent right lumbar pain of 41-year-old-male with previous history of scrotal tu, imaging with MRI and detection of retroperitoneal fusiform mass from L5 up to but not into foraminal level L5/S1 compatible with PNST. On clinical exam no sensorimotor deficit. Surgical removal via navigated focused retroperitoneal approach in supine position with lateral abdominal incision; tu removal after placement of ring retractor system via microsurgical intrafascicular extirpation. Postoperatively without deficit.

LSP Tu zone II, Spi extension ( Fig. 10 )

Fig. 10.

LSP Zone-II tumour with intraspinal extension (Spi). Clinically severe progressive right sciatica with S1 hypesthesia, no motor deficits. On pre-operative coronal MRI above- and subpromontory, retroperitoneal mass (A) behind psoas muscle (Zone II) with intraforaminal to intraspinal L5/S1 extension on axial (B, mass behind psoas, in L5/S1 neuroforamen and intraspinal encircled with dotted line). Surgical removal via combined biportal approach in lateral decubital position from anterior via abdominal to flank incision for retroperitoneal Zone II part (C, incision marked by dotted line, triangle on midline pelvis, asterisk in cranial direction) and from posterior via horizontal incison centred over L5/S1 disc (D, incision marked by dotted line, triangle on pelvis, asterisk in cranial direction) for intraforaminal to intraspinal extension. Post-operative MRI depicting tumour removal in coronal (E) and axial view (F, arrow on nerve root under psoas, low density signal on removed right L5 hemilamina).

Severe sciatica to right leg in S1 distribution to popliteal fossa in 58-year-old-male, worsening rapidly with resting and night pain. No prior tumour history. On imaging 10 × 7 cm mass, elevating the psoas by 5 cm and extending to L5/S1 intraspinal, walling in the right L5 root. On clinical exam hypesthesia to dorsal thigh, no motor deficit, normal voiding. Tu approached in one stage via biportal approach with combination of antero-lateral transabdominal approach with flank incision for retroperitoneal exposure and dorsal spinal approach cantered over Disc L5/S1 from mid to right lateral for intraspinal-transforaminal approach. Lateral-decubital patient positioning. Tu removal with sustained sciatic and femoral nerve function, partial S1 graft reconstruction.

LSP Tu Zone II to III, Sci extension ( Fig. 11 )

Fig. 11.

LSP Zone II & III tumour with sciatic/infrapiriform extension (Sci). Pelvic imaging due to detrusor-sphincter work-up, without radicular or other pain on fully ambulant patient without sensorimotor deficits. Patient difficult to assess due to previous severe traumatic brain injury. Pre-operative MRI with subpromontory pelvic mass of mixed signal intensity in sagittal (A, arrow towards mass, asterisk on promontory)), reaching from left central (Zone III) over psoas (Zone II) and extending caudal on sciatic route to infrapiriform subgluteal (B, arrow towards mass). Surgical approach with midline abdominal incision, transperitoneal in a supine da Vinci position (C, lateral view), (D, view from above). Objective was to remove tumour in staged fashion with second, separate surgery from a dorsal sub-to transgluteal approach in prone position. Histopathology revealed gastrointestinal stroma tumour (GIST). Post-operative MRI imaging after first surgery depicting removal of Zone-II & III tumour part (E, sagittal view) and remaining infrapiriform tumour extension (F, encircled tumour residual).

Imaging due to unclear pelvic pain in 34-year-old female patient with status post previous severe TBI (right temporo-mesial to thalamic intracranial contusion sand haemorrhage) leaving her with distinct cognitive impairments. On MRI pelvis and PET CT scan confined, inhomogeneous, subpromontory lateral to central mass on the left (zones II and some III) with infrapiriform extension along sciatic route. Lesion well confined however with inhomogeneous inner signal, relation to plexus and nerves cannot conclusively be resolved, size up to 10 cm. Clinically, no radicular, nor resting pain, detrusor-sphincter dyscoordination previously known as well as urge-incontinence since childhood, other than that normal voiding. On exam no paresis of lower or upper extremities with increased reflexes of left upper and lower extremity.

Surgical approach was midline transperitoneal in supine da Vinci position for exposure from midline to latero-caudal to have good control over iliacal vein and artery. Partial removal was anticipated and staged secondary surgery planned from a dorsal infrapirifom sub-to transgluteal approach. Tumour highly vascularised. Patient without new post-op deficits. Pathology revealed malignant gastrointestinal stroma tumour (GIST), patient so far did not opt for second surgery.

3.10. Translating zone system into surgery-condensed workflow

For zone identify main mass of tumour and relate it to following landmarks on MRI. BP Zone translates in surgical approach as per Table 2.

• •Clavicle, above (Zone I), or below (Zone II)
• •Axilla, within (Zone III), which is lateral to lateral border of pectoralis minor
• •Cervico-thoracic midline substantially involved (Zone IV)

LSP Zone gives approach according to suggestions in Table 5.

• •Promontory, above (Zone I) or below (Zone II or III)
• •Psoas (pelvic portion), under or lateral to (Zone II), medial to or central (Zone III)

Tumour extension considerably past Zone on MRI will lead to additional approach selection and thus guide decision on positioning/draping in single stage surgery.

BP tu extensions correspond to Table 4 and Fig. 1.

• •For-Neuroforamen (plexus-, antero-lateral-, or dorsal spinal approach)
• •Spi-Spinal canal (antero-lateral or dorsal spinal approach)
• •Scap-Scapula (subscapular approach)
• •Ltw-Lateral thoracic wall (axillary or lateral thoracic wall approach)

LSP tu extensions as per Fig. 7 an 8 translate into following anatomical regions.

• •Fem-along femoral nerve course (infrainguinal approach)
• •Sci-along sciatic nerve course, infrapiriform (trans- or subgluteal approach)
• •For-Into neuroforamen, along root course (anterior, lateral or dorsal spinal approach)
• •Spi-into spinal canal (dorsal spinal approach)

4. Discussion

If the brachial- or lumbosacral plexus is tumour affected (plexus “associated tumours”) it is advised to have surgery in hands of plexus and PNST experienced microsurgeons to minimize surgical morbidity. Due to risks and limitations of percutaneous biopsy it is most of the times not advised from a nerve surgeons’ perspective. However, this is highly controversially discussed between sarcoma and nerve surgeons (Perez-Roman et al., 2020), as classic soft tissue sarcoma needs prior biopsy to avoid seeding by approach and ensure negative margins if complete resection is possible (Casali et al., 2018). The EANO and current German sarcoma guidelines (S3-Leitlinie Adulte Weichgewebesarkome, 2022) explicitly recommend: “The gold-standard technique for biopsy is multiple percutaneous core biopsies (preferably ≥16G) or open incisional biopsy [85], [86], [87].If this is not possible or does not yield a result, an open excisional biopsy may be performed for superficial lesions [86]. “

It needs to be kept in mind, that in peripheral nerve sheath tumours, not only the mass itself can affect nerve function and lead to neuropathic pain by direct compression and encasing. Neoplasia can also provoke inflammation and perineural microlesions at adjacent peripheral nerves (Cohnen et al., 2020).

Thus, prior to surgery the tumour entity might not have been ascertained yet. Benign PNST will be the most frequent diagnosis, and removal by extirpation necessitates intrafascicular dissection technique with intermittent fascicular motor stimulation testing in a sometimes very confined dissection space. Otherwise, a benign tumour will be resected leaving a nerve gap with resulting complete functional loss (Guedes et al., 2024; Kretschmer et al., 2007; Levi et al., 2010). In cases of potential malignancy approach choices should inherently implement options for approach extension or redo surgery. At times a classic sarcoma surgery approach might not be in the best interest of the patient (Martin et al., 2020). This should be accounted for at primary surgery. With these givens, approach choices and their combinations are crucial for function sparing. Apart from tumour localisation, the needed surgical exposure extent is dependent on the surgical objective. It can be limited to or include any of the following: securing a histopathological diagnosis, pain relief, prevent tumour spread and condition worsening; thus improve-, sustain-, or prolong survival sometimes at the cost of function. In NF 1 patients the objective might be to remove only one of an accumulation of peripheral nerve sheath tumours (e.g. in plexiform neurofibromas) with a focused approach due to malignant changes on imaging (e.g. hot spot in FDG-PET CT or MRI scan). Surgical technique applied can thus be limited, or escalated to decompression, biopsy, fascicle and function sparing intrafascicular tu extirpation under motor response monitoring, subtotal function sparing resection, total resection with tu free margins or compartment resection with nerve and vascular amputation with and without nerve and vascular reconstruction.

Having performed surgery for plexus tumours for long we saw the need for ourselves to deduct the basic principles for our approach choices when the lumbosacral plexus was affected. This was due to high individuality and the ever-changing demands of surgery related to the objective of surgery. This led to our first decision pathway (Heinen et al., 2020) that was refined (Kretschmer and Heinen, 2025) and herewith turned into a zone system with extensions applicable to the brachial- and lumbosacral plexus.

4.1. Relevance and limitation

Published series describe outcomes for PNST surgery in the brachial plexus and list the various approaches used. For the lumbosacral plexus a decision-making process has been described (as referenced above). However, so far, no uniform and systematic classification of BP- and LSP tumours have been suggested, that allows to guide and deduct apt approach choices and combinations for tumour surgery.

The introduced classification in its purest sense is a guided think path based on anatomic landmark attribution that aids to choose and combine approaches. It is not a guide that automatically leads to better surgery for these entities. Experienced plexus tu surgeons if aware or unaware automatically go through such a thinking process. Like always there will be exceptions that will not fit the suggested categories, especially when the pendulum swings to more classic sarcoma surgery with its inherent principles: aiming at R0 resection, meticulous measures to avoid seeding, and thus sometimes amputation of functioning nerve structure. Nevertheless, the authors believe that our suggested simplistic categorisation covers a substantial amount of different complex plexus tumours and aides the presurgical decisions and preparations if used.

5. Conclusion

For the first time an interrelated classification system of Plexus tumour is reported and graphically described to aid in plexus tumour surgery. It is simple and enables systematic approach decisions that help to reduce risk and optimize tissue sparing exposure.

Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Co-author, Dr. Christian Heinen is an editor for the Peripheral Nerve special edition of Brain and Spine journal. Other than that the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Handling Editor: Dr W Peul