Giant cell tumour of tendon sheath: A 10-year study from a tertiary care centre.

IntroductionCytology of giant cell tumour of tendon sheath (GCTTS) is often sufficient to diagnose this lesion and has been previously described in small series. The present study was undertaken to evaluate detailed cytomorphological features and differential diagnostic entities and pitfalls in the diagnosis. MethodsAll the cases of GCTTS reported on FNAC were retrieved from July 2007 to June 2017. The cases were reviewed for various cytomorphological features, which were correlated with follow-up histopathology wherever available. ResultsA total of 72 cases of GCTTS were retrieved, follow-up histopathology was available in 20 cases. The common sites of involvement were fingers and palm followed by wrists, elbow, knee, ankle and shoulder. The characteristic cytomorphology consisted of mononuclear cells, multinucleated giant cells and pigment laden macrophages in variable numbers. There were four discordant cases that were confirmed on histopathology as sarcoidosis, melanoma, fibrous histiocytoma and eumycetoma. ConclusionsGCTTS can be confused cytologically with giant cell rich lesions of bone and soft tissue and pigment containing lesions including melanoma. Ladybird cell is a characteristic feature seen in this lesion. Proper clinicoradiological correlation is essential before offering a diagnosis of GCTTS on cytology. Cytology of giant cell tumour of tendon sheath (GCTTS) is often sufficient to diagnose this lesion, however it can mimic with other giant cell rich lesions and pigment containing lesions including melanoma. Lady bird cell is a characteristic feature seen in this lesion. We evaluated various cytomorphological features and differential diagnostic entities of this lesion.