Microsurgical interfascicular dissection operation is a viable treatment of carpal tunnel syndrome caused by Lipofibromatous hamartoma: A case report

Abstract

Lipofibromatous Hamartoma (LFH) is a rare and slow growing benign tumor affecting the peripheral nerves, which usually involves the median nerve. Median nerve involvement commonly causes pain, numbness, paresthesia and carpal tunnel syndrome (CTS). This article describes a case of lipofibromatous hamartoma in a 6-years-old girl, complained of the mass and numbness in her left distal forearm. Microsurgical interfascicular dissection operation was performed to remove the epineural proliferation tissue, numbness disappeared after the operation. At the 12-months follow-up appointment she remained asymptomatic and there was no change in mass size.

Highlights

• •Performed microsurgical interfascicular dissection, where the tumor tissue was removed very carefully so as not to damage the nerve tracts and the result is satisfaction.
• •A small portion of the tissue was excised for biopsy and the final histological examination showed the diagnosis of LFH
• •Run immunohistochemistry and it demonstrates: Desmin(-), Ki-67(-), SMA(+),S100(-),Vim(+) highlights the hyperplasia of fibro-neural hyperplasia.

1. Introduction

LFH was first described by Mason in 1953 affecting the peripheral nerves with different clinical presentations. LFH is often found in the upper extremity which is excessive proliferation of fibroadipose tissue infiltrates the epineural and perineural elements of peripheral nerves, the median nerve is the most commonly affected nerve (80 % of cases) followed by the ulnar and radial nerve [1], [2]. The etiology of LFH is still unknown but it likely has a congenital or developmental origin with the majority of the tumors occur among children [3], [4]. It is also unknown why the median nerve is most commonly affected [5].

The diagnosis of LFH can be made with ultrasound CT and MRI. Biopsy and histopathological examination are the only definitive ways to diagnose LFH. Histological analysis revealed interwoven collagen, fibroblasts, mature adipocytes, and occasional capillaries that separate nerve tracts and infiltrate the space between the epineurium and perineurium [6].

There is no definitive treatment for LFH and the treatment options for LFH are guided by the severity of the symptoms which range from close observation to complete nerve resection.

The pathology of LFH is still unclear which needs further research to better understand its pathophysiology and to determine the best treatment option for it based on patient characteristics.

2. Case presentation

A 6-years old girl presented to our outpatient orthopedic center for a slow growing mass in her left distal forearm on 30th August 2019 (Fig. 1). Her parents said the mass was noticed by the family first time one year ago. After taking her to a local hospital, they did not give her any special treatment but went home to observe the changes in the mass. The mass growing slowly without pain or any other symptoms until the girl felt numbness two months ago. There was non-special in her medical, surgical, drug, allergies and family history.

Fig. 1.

The Clinic picture showed a mass from the distal forearm to the palm of the left hand (yellow ring). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Physical examination showed a 3 ∗ 1.5 cm, localized, longitudinally, soft, non-tender subcutaneous mass in her distal forearm. There was numbness in the thumb. No movement of the mass by fingers or wrist flection and extension, no motor defects, no thenar muscle atrophy, no abnormal of radial pulse and capillary refill. Tinel's sign and Phalen's test were both positive (Fig. 1). All laboratory investigations and Radiograph were normal (Fig. 2).

Fig. 2.

Anteroposterior and lateral radiographs of the left forearm showed no abnormal findings.

Magnetic resonance imaging (Fig. 3)demonstrated the median nerve was fusiform swelling from the distal forearm to the proximal palmar area and was pressed into an hourglass shape by the transverse carpal ligament. The mass measured 12 cm proximal-distal extension with 2.0 × 1.0 cm in transverse by anteroposterior dimensions. In the coronal cut, the mass was shown as coaxial cable. In the coronal and sagittal cut, it was shown as spaghetti string. Both T1 weighted and T2 weighted images showed thickened hypointense nerve fascicles interspersed within hyperintense fibroadipose tissue.

Fig. 3.

Magnetic resonance imaging findings. A: Axial T1 weighted image of shows thickened hypointense nerve fascicles surrounded by hyperintense fibroadipose tissue giving “coaxial cable” like appearance and the displacement of the flexor tendon and palmar protrusion of the flexor retinaculum due to an enlarged median nerve (red arrow).B and C: The coronal and sagittal sections shows “spaghetti” like appearance of the mass, fusiform or hourglass enlargement of the median nerve (white arrows) with low-signal intensity nerve bundles embedded in hyperintense adipose tissue. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Surgical treatment was determined under the diagnosis of CTS caused by the mass which was exposed through an 8 cm long incision extending from the distal forearm to the proximal palm, under general anesthesia and tourniquet control on 3rd September 2021. After dissecting the subcutaneous tissue, the mass was identified along the normal median nerve and was severely compressed in the carpal tunnel. The outer membrane of the mass was formed along the epineurium of the median nerve and no infiltrations into the surrounding tissues (Fig. 4). The transverse carpal ligament was carefully released along the ulnar border, then microsurgical interfascicular dissection operation was performed to remove the epineural proliferation tissue as much as possible. A small portion of the tissue was excised for biopsy. The final histological examination showed the diagnosis of LFH (Fig. 5).

Fig. 4.

A: intraoperative photographs of the girl with lipofibromatous hamartoma in her left distal forearm (red arrow). B: remove the epineural proliferation tissue, “spaghetti” like appearance of the mass. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5.

A: HE histopathological findings: normal nerve fascicle surrounded by fibroblasts and mature adipocytes and connective tissue B: Immunohistochemistry demonstrate: Desmin(−), Ki-67(−), SMA(+),S-100(−),Vim(+)highlights the hyperplasia of fibro-neural hyperplasia.

The postoperative recovery was uneventful, with healed surgical wounds and no signs of infection，no neurological deficit. Numbness disappeared after the operation and the girl returned to normal life at the postoperative day 10. At the 12 months follow-up appointment she remained asymptomatic and there was no change in mass size. The work has been reported in line with the SCARE 2020 criteria [7].

3. Clinic discussion

The most common symptoms in patients with LFH are a painless masse on the distal forearm which gradually increase in size. As the tumor grows, the patient begins to develop symptoms of nerve compression, with paresthesia and motor abnormalities in the affected nerve areas, such as carpal tunnel syndrome. There have been no clear guidelines established for the diagnosis of LFH [8].Ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) can be used to diagnosis of LFH. US displays an enlarged hypoechoic median nerve containing discrete hypoechoic coaxial cable like bundles encased by an echogenic substratum [9], [10]. CT revealed a discus bulging mass in the carpal tunnel with flexor tendon displacement. The mass density shows the fibroblast component [11]. MRI shows fusiform enlargement of the affected nerve containing thickened axonal bundles encased in epineural fibrous tissue giving “coaxial-cable” like appearance on axial images and “spaghetti” like appearance on coronal images [12]. An MRI alone is adequate to make a diagnosis, thus a biopsy is not necessary [13], [14].In our case, MRI diagnosis of the extent of nerve involvement was accurate and compatible with surgical finding, which was very important for surgical planning. The tissue we took from around the nerve tracts was filled with collagen fibers, adipocytes and myofibroblast tissue. We ran an immunohistochemical test, and the results support neuro-fibrous hyperplasia.

There is no definitive treatment for LFH and the treatment options for LFH include a wide range from close observation to complete nerve resection [8] [15].Complete tumor resection eliminates the risk of malignancy and the possibility of recurrence. However, severe sensory and motor disturbances can be left in the innervated area, and painful neuroma can form at the broken end of the nerve, given the potentially disastrous consequences and the benign nature of LFH, radical resection is not recommended [16], [17]. Thus, most authors advocate close observation is recommended for patients without neurological symptoms and carpal tunnel decompression for median nerve in symptomatic patients [4], [18]. In recent years, successful endoscopic carpal tunnel release has been reported for LFH [19]. Some authors have reported good results with debulking surgery and invasive interfascicular dissection [8], [20]. Microsurgical dissection produced disappointing results [21]. In our case, we performed interfascicular dissection, where the tumor tissue was removed very carefully so as not to damage the nerve tracts. At the last follow-up, the patient complained that numbness in thumb and index finger disappeared and the size of the mass unchanged.

4. Conclusion

In conclusion, LFH is a rare slow growing benign tumor affecting the peripheral nerves with different clinical presentations. The diagnosis of LFH can be made with ultrasound, CT and MRI without the need for a biopsy. In our case, the LFH was symptomatic, therefore, we decided to perform a microsurgical interfascicular dissection operation and the result is satisfaction.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Source of funding

No funding, grants, or in-kind support in support of the research or the preparation of the manuscript.

Ethical approval

The study is exempt from ethnical approval in our institution.

Consent

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of written consent is available for review by Editor-in-Chief of this journal on request.

CRediT authorship contribution statement

Li Li: conceived the study.

Shu-Qing Feng: collected data.

Zhi-min Mao: analysed data.

Xiao Yun: prepared and drafted the manuscript, edited manuscript and reviewed the manuscript.

Research registration

N/A.

Guarantor

Xiao Yun

Declaration of competing interest

No conflict of interest exits in the submission of this manuscript, and manuscript is approved by all Authors for publication. I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously and not under consideration for publication elsewhere in whole or in part. All the authors listed have approved the manuscript that is enclosed.