Aggressive pilomatrixoma: a diagnostic dilemma on fine-needle aspiration cytology with review of literature.

We report a case of aggressive pilomatrixoma (PMX) in a 25-year-old male who presented with swelling in left supraclavicular region of 2-month duration. A diagnosis of small round cell tumor was suggested on fine-needle aspiration cytology. He underwent wide excision of the mass. On histomorphological examination, a diagnosis of aggressive PMX was made. The swelling recurred after 3 months of complete resection and on examination had similar morphological features. The case is presented because of the potential diagnostic difficulties on cytological examination and rare occurrence of aggressive variant of PMX.