Pigmented Villonodular Synovitis Masquerading as a Metastasis: Imaging Features and Coaxial Needle Biopsy Technique

Abstract

Pigmented Villonodular Synovitis (PVNS) of the shoulder is rare. We present a patient with locally recurrent tonsillar squamous cell carcinoma (SCC) and newly identified soft tissue lesion of the right shoulder exhibiting similar focal FDG-PET CT uptake. Biopsy demonstrated features consistent with pigmented villonodular synovitis (PVNS). We discuss imaging features and describe a ‘ two needle,’ coaxial biopsy technique.

Introduction

Pigmented villonodular synovitis (PVNS) is a chronic mono-articular neoplastic disease that typically involves a single joint.¹ It usually affects the knee or hip with characteristic overgrowth of the synovial lining. While not malignant, local joint tissue proliferation can be difficult to manage surgically and can cause chronic joint swelling leading to arthritis.¹

Although rare, PVNS is known to be FDG-avid on PET/CT, with limited reports describing shoulder involvement.² We present a patient with locally recurrent tonsillar SCC and newly identified soft tissue lesion of the right shoulder exhibiting similar focal FDG-PET CT uptake. MRI features were atypical of soft tissue metastasis, therefore CT-guided biopsy was performed. Biopsy confirmed characteristic histological features of PVNS. We used a two needle, coaxial biopsy technique not widely described in current literature; a technique we believe to be ideal for surgically inaccessible lesions or for deep lesions within the shoulder.

Case Report

A sixty-year-old female with a background of tonsillar squamous cell carcinoma (SCC), treated with radical chemo-radiotherapy, presented with local neck recurrence after three years. She was re-staged in anticipation of a salvage radical neck dissection, segmental mandible resection and flap reconstruction. Restaging CT was carried out as any metastasis outside of the neck would exclude her from the proposed radical surgery. There was no other relevant past medical history of note.

FDG-PET/CT demonstrated intense uptake within the locally recurrent tonsillar SCC and also intense uptake adjacent to the right anterior glenoid with a SUV max of 6. Both soft tissue lesions showed similar imaging appearances on FDG-PET CT (Fig. 1a-d). However, the patient was asymptomatic in her right shoulder. Following multidisciplinary discussion, SCC metastasis or soft tissue sarcoma was considered as the main differential diagnosis.

Figure 1.

(A and C) shows a focal area of increased uptake in the left tonsil in keeping with recurrent tonsillar squamous cell carcinoma. (SUV max of six). (B and D) shows an avid area of uptake anterior to the right glenoid. Both lesions showed similar SUV max values of 6.

Magnetic resonance imaging (MRI) (Fig. 2a-f) showed a 2x3cm oval shaped lesion anterior to the right glenoid, deep to the subscapularis muscle. The lesion was isointense to muscle on T1 and slightly hyperintense on fat suppressed imaging. Unfortunately a gradient echo sequence was not performed, as PVNS was not on the list of differential diagnoses. Ultrasound demonstrated a solid mass with mild increased signal on Doppler. As imaging features were inconclusive, CT-guided biopsy was performed to obtain a definitive sample for histology and exclude metastatic disease prior to radical surgery.

Figure 2.

MRI T2 axial (A), STIR axial (B,D), T1 coronal (C) sequences shows an iso intense 2x3cm well defined lesion in relation to the anterior part of the glenoid but not directly involving the scapula. T1 axial fat saturated (E) and coronal (F) post contrast images show a modest enhancement pattern. The overall MRI appearances were non specific.

Under CT guidance, an 8-gauge T-lok bone marrow biopsy needle (Argon medical devices, USA)³ was first introduced into the right shoulder, via the deltopectoral groove, and advanced deep to the subscapularis muscle with the tip proximal to the lesion, anterior to the glenoid. A 14-gauge supercore soft tissue needle (Argon medical devices, USA)³ was then placed through the outer 8-gauge needle (Fig. 3a-c). Multiple core biopsies were taken of the lesion and sent for histology (Fig. 4a-b). The procedure was performed under conscious sedation, using ropivicaine for local anaesthetic, without complication. Histology revealed typical features of PVNS (Fig. 5a-d). She was managed symptomatically for her PVNS. She underwent radical neck dissection for recurrent tonsillar SCC.

Figure 3.

(A) shows the 8 gauge bone marrow biopsy and 14 gauge soft tissue biopsy needle on the left and right respectively. (B) shows how the soft tissue needle is placed through the bone biopsy needle. (C) shows a close up view of the trochar needle tip.

Figure 4.

(A and B) show CT guided biopsy of the anterior glenoid lesion with T-lock bone biopsy needle and supercore soft tissue needle.

Figure 5.

(A) Low power magnification of biopsy showing features of tenosynovial giant cell tumour (pigmented villonodular synovitis) composed of sheet like arrangement of mononuclear cells with scattered multinucleated giant cells (HE stain x100 original magnification). (B) Higher power view of the tumour showing the oval mononuclear cells with round nuclei lacking cytological atypia or atypical mitoses and admixed multinucleated giant cells (HE stain x400 original magnification). (C) Focal areas in the tumour showing foamy histiocytic infiltrate (HE stain x200 original magnification). (D) Focal haemosiderin pigment deposition is also noted in the tumour (HE stain x200 original magnification).

Discussion

PVNS can be focal or diffuse and can present as an intra or extra-articular form. It usually presents in the third to fifth decades of life, with varied clinical symptoms including pain, soft-tissue mass, swelling and joint dysfunction.³ Radiographs and Computed tomography (CT) are often non-specific. If there is intra-articular involvement, radio-graphs may show erosions of the affected joint.³

MRI is certainly more specific than radiographs or CT. MRI may demonstrate several features suggestive of PVNS including non-specific intermediate low signal intensity on T1 and T2, and a blooming artifact on diffusion gradient echo sequences caused by hemosiderin deposits.³ However, in our case no specific imaging features to indicate aetiology were present, so biopsy was performed as it would dramatically alter patient management.

There is limited literature discussing the imaging features of PVNS on nuclear medicine modalities. PVNS is known to be FDG-avid, a SUV max of 11.3 has previously been reported.⁴ Moreover there are a number of case reports of PVNS as an incidental findings on FDG-PET/ CT in the setting of known malignancy.⁵ As in our case, this posed a diagnostic challenge to differentiate between metastasis and other potential disease entities.

Studies have also shown no statistical difference in SUV max between PVNS subtypes including intraarticular PVNS, diffuse PVNS, or giant cell tumour of the tendon sheath.⁵ PVNS has also been shown to respond to cancer treatment with subsequent decrease in metabolic activity.⁶ These findings can complicate patient work up, more so in conditions such as melanoma or sarcoma where metastatic musculoskeletal disease manifestations are common. Depending on the form (localized vs. diffuse), radiation may be considered in conjunction with surgical excision. In diffuse PVNS, synovectomy is usually necessary.

The described biopsy technique using a two needle coaxial technique is an alternative method to obtain diagnostic tissue. Percutaneous biopsy using a single coaxial needle system method is commonly used currently. The coaxial needle technique is an alternative and more efficient method, which we have used successfully as in this case without any complication. It facilitates multiple soft tissue cores to be obtained rapidly with minimal soft tissue trauma as the outer needle stays in place between samples being taken.

Learning Points

• There are only a handful of case reports describing PVNS in the shoulder, implying it is a very rare location.

• A metabolically active lesion near but not directly involving the scapula should raise the suspicion for a coexistent disease process. Despite the known history of cancer, a metastatic lesion should not be conclusively diagnosed from PET imaging alone if imaging features are not characteristic.

• We present a two needle coaxial biopsy method using CT which can facilitate rapid tissue sampling.

Conclusions

There are a number of case reports of PVNS as an incidental finding on FDG-PET/CT in the setting of known malignancy. With the ever increasing use of PET imaging within oncology, it is likely that potentially benign but metabolically active lesions will be identified more frequently. This can complicate treatment and delay patient work up. If typical MRI imaging features are present, then PVNS can be confidently diagnosed. However, if atypical or in an unusual location, we describe a two needle CT guided biopsy technique to confirm the diagnosis.