Cytomorphology of pleomorphic fibroma of skin: A diagnostic enigma
A 38-year-old male presented with a superficial, painless, polypoidal, soft tissue mass since 6 months, measuring about 3 × 1.5 cm in size, and involving the back of the thigh. Fine needle aspiration cytology (FNAC) was done and slides were stained with Giemsa stain. The aspirate yielded cellular smears. Background showed metachromatic stromal fragments. Cells were pleomorphic having very large nuclei (monster cells) with scanty cytoplasm. Few of the nuclei showed single nucleoli []. Nuclear membranes frequently showed notches, creases, or folds. Cells were lying singly and occasionally forming clusters. These were admixed with the spindle cell component along with few multinucleated cells. Necrosis and mitotic figures were not seen in smears. On FNA, the swelling was diagnosed as fibrohistiocytic lesion with atypical cells and the mass was subsequently excised.\nOn gross examination, the mass was well circumscribed measuring 3 × 1.5 cm. The cut section was solid, grayish-white, and fibrous. Routine processing and hematoxylin and eosin staining were done. Microscopically, tumor showed thick bundle of haphazardly arranged collagen in the dermis. Spindle- and irregularly shaped stellate or multinucleate cells were scattered between the collagen bundles. These cells were markedly atypical showing scant cytoplasm and large, pleomorphic, enlarged hyperchromatic nuclei with small nucleoli []. No mitosis or necrosis was evident in multiple sections examined. Based on these features, diagnosis of PF was made.\nImmunoprofile of lesional cells revealed positive staining for vimentin [] and CD34 and negative staining for S-100.