Infarcted Tenosynovial Giant Cell Tumors: Multi-Institutional Analysis of 80 Cases Highlighting Consultation Patterns...

Tenosynovial giant cell tumor (TGCT) is a benign neoplasm of synoviocytic differentiation composed of variable proportions of neoplastic mononuclear cells (synoviocytes) and non-neoplastic multinucleated giant cells, foamy macrophages, siderophages, lymphocytes, plasma cells, and hemosiderin deposits. Although TGCT is usually readily diagnosed histologically, it may exhibit limited or extensive infarct-type necrosis that obscures diagnostic features and raises concern for malignancy. To better characterize this phenomenon, we analyzed TGCTs with infarct-type necrosis in a multi-institutional cohort. The authors' institutional and consultation archives were searched for TGCT with infarct-type necrosis. All available slides were re-reviewed, and clinicoradiologic data, including contributor-provided suggested diagnoses, were recorded. Eighty cases were identified (42 females, 38 males) with a mean age of 36 years (range: 8 - 81). Tumor sites included knee (55; 69%), hands/feet (15; 19%), hip (9; 11%), and infratemporal region (1; 1%). Mean tumor size was 2.9 cm (range: 0.7- 8.3 cm). Preoperative clinical or radiologic impressions were available in 64 cases (80%): TGCT was suspected in 41 (64%), a non-neoplastic process in 16 (25%), and 7 were non-specific masses (11%). More than half of the cases (53%) were pathologist-driven consultations, and contributor-suggested diagnoses were provided in 29 instances; nearly all (26/29; 90%) reflected uncertainty related to the presence of necrosis, including at least 4 cases in which malignant TGCT was considered. Most tumors (65; 81%) showed >50% necrosis, and 30 cases (38%) demonstrated complete or near-complete necrosis (>95%). Ancillary studies were performed in 14 cases (18%). Neoplastic synoviocytes expressed CSF1 mRNA and clusterin, rarely were desmin-positive, and demonstrated a characteristic peripheral rim of hemosiderin with histochemical iron stains. CD68 and CD163 immunostains identified background histiocytes. Follow-up data was available for 32 patients (40%; mean: 48 months; range: 4-185 months); all were without evidence of disease following surgical excision. We conclude that TGCT may exhibit extensive infarct-type necrosis and thereby mimic a non-neoplastic process or sarcoma; awareness of this phenomenon, along with clinical and radiologic correlation, should facilitate accurate diagnosis.