Fine-needle aspiration cytology of giant cell tumor of tendon sheath.

Giant cell tumor of tendon sheath (GCTTS) is a unique soft tissue lesion of the hands and feet. As the cytomorphological features of this lesion are rarely documented, the spectrum of cytomorphological features in 20 cases of GCTTS seen in fine-needle aspiration (FNA) smears are presented. Patients were in the 12-64-yr age group with an equal sex ratio. Fingers or thumb were the commonest site (16 cases), followed by foot (3 cases) and palm (1 case). FNA smears were cellular and composed of varying proportions of stromal and giant cells. Stromal cells showed a dispersed arrangement and were polygonal to spindle shaped. Nuclear grooves and convolutions were found in some of the stromal cells in all cases. Intranuclear cytoplasmic inclusions were occasionally seen. Polygonal cells with round nuclei and nucleoli having abundant cytoplasm, along with binucleate forms, were also found in all cases. Histological sections were available in 10 cases and corroborated the cytological features. Hemosiderin-laden macrophages (11 of 20 cases) and abundant foamy vacuolation of stromal cells (3 of 20 cases) were also observed in FNA smears. In tissue sections, both features were seen in all cases, but with a patchy distribution. The cytological features of GCTTS are uniform, and FNA cytodiagnosis is possible.