Extra-articular pigmented villonodular synovitis of the gluteus

A 60-year-old woman presented to us with newly diagnosed breast cancer. She had a screening mammogram that revealed loose collections of punctate and linear calcifications on the left breast with ultrasound showing two to three poorly marginated hypoechoic zones. Breast biopsy was consistent with ductal carcinoma in situ with microinvasion. She underwent mastectomy with negative sentinel lymph node biopsy.

On review of systems, she admitted to intermittent left thigh numbness with tingling sensations down to her toes for the past eight years. Physical examination did not reveal any focal neurologic deficit and straight leg raising test was negative.

Axial contrast-enhanced PET/CT images demonstrating a heterogeneously enhancing mass in the posterior left thigh anterior to the left gluteus maximus muscle (a). Corresponding functional images demonstrate heterogeneous hypermetabolic activity with a maximum SUV of 3.6 (b). Symmetrically increased uptake in the abductor muscles of the thighs is related to recent physical activity. Photos courtesy of M. Ghesani, MD

Preoperative PET/CT scan showed hypermetabolic activity of the left breast malignancy and an 8 cm × 8 cm × 5 cm heterogenously enhancing mass anterior to the left gluteus maximus muscle compressing the left sciatic nerve (SUV 3.6). The mass was suspicious for synchronous neoplastic lesion. Differentials are: sarcoma or nerve sheath tumor.

A follow-up MRI of the left hip and buttocks showed an enhancing heterogenous soft tissue mass between the deep muscle planes of the posterior hip/upper thigh suspicious for sarcoma measuring 3.8 cm × 10.5 cm ×12.2 cm. This mass contained cystic component and calcification/hemosiderin.

The patient then had a left buttock biopsy; pathology was soft tissue fragments with mononuclear histiocytoid cells forming pseudosynovial and pseudoglandular spaces, sheets of foam cells with scattered hemosiderin laden macrophages and rare giant cells. Immunohistochemical stains were positive for vimentin, CD68 and focally with desmin, and were negative for AE 1/AE 3, CK 7, S100, BRST-2, MDM2, compatible with pigmented villonodular synovitis (diffuse type giant cell tumor).

She is referred to an orthopedic oncologist for possible surgical resection.

Axial MRIs of the left hip. Fat-suppressed T2 (a), T1 (b) and fat-suppressed T1 (c) images demonstrating cystic and solid components, with areas of hemosiderin and/or calcification. There was heterogenous enhancement on the postcontrast images (d). Photos courtesy of M. Ghesani, MD

Discussion

Diffuse-type giant cell tumor is an extra-articular fibrohistiocytic tumor, which together with localized extra-articular and intra-articular forms (otherwise known as pigmented villonodular synovitis) are collectively termed as fibrohistiocytic tumors. It was first described by Jaffe and colleagues and typically arises from synovial lining, bursae and tendon sheaths. Grossly, it appears as thickened synovium with villous and nodular patterns, and microscopically with proliferation of synovial-like cells and histiocytes.

Several hypotheses about its exact causality were attributed to repeated nontraumatic inflammation, localized lipid metabolic derangement or response to blood products within the joints. Recently, it has been considered to represent benign neoplasia due to its autonomous growth.

Diffuse-type giant cell tumor is an extra-articular form of pigmented villonodular synovitis. It is mostly located in the periarticular soft tissues and is rarely purely subcutaneous or intramuscular. Localized forms are common; 85% of these occur in the fingers. Pigmented villonodular synovitis occurs more in men; giant cell tumor is slightly more prevalent in women.

MRI has a high diagnostic value for both intra- and extra-articular types with features of joint effusion, hyperplastic synovium and low signal intensity signifying the hemosiderin deposits. The diagnosis can only be confirmed by biopsy, which is consistent with characteristic fibrous stroma, hemosiderin deposition, histiocytic infiltrate and giant cells.

They are slow-growing benign tumors and are treated with surgical excision. Pigmented villonodular synovitis has been reported to have as high a recurrence rate as 9% to 44%.

Irene Dy, MD, is a Fellow in Hematology and Oncology at St Luke’s-Roosevelt Hospital Center.

Seth Cohen, MD, is an Attending Oncologist at St Luke’s-Roosevelt Hospital.

Iwao Tanaka, MD, is a Resident in Radiology at St.Luke’s-Roosevelt Medical Center.

Carlos Benitez, MD, is a Musculoskeletal Radiologist at St. Luke’s Roosevelt Hospital Center and Assistant Professor of Clinical Radiology at Columbia University, College of Physicians and Surgeons.

Munir Ghesani, MD, is Associate Clinical Professor of Radiology at Columbia University College of Physicians and Surgeons and Attending Radiologist at St. Luke’s-Roosevelt Medical Center.

For more information:

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• Sanghvi DA. Skeletal Radiology. 2007;36:327-330.
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