Fine needle aspiration cytology of pilomatrixoma and differential diagnoses.

Objective: To review the cytologic features of pilomatrixoma to allow a definitive diagnosis at the time of aspiration and correct patient management.
Study Design: Three patients each presented with a mass lesion and on fine needle aspiration were diagnosed as either having pilomatrixoma or a benign skin adnexal tumor. The diagnosis was confirmed on histology. A retrospective analysis of the cytology was performed.
Result: The most consistent and predominant features for diagnosis were basaloid cells, anucleate squamous cells and calcification in an inflammatory background, often with giant cells. Only focal evidence of true shadow or "ghost" cells was seen in one case on the Diff-Quik smear. Therefore, lack of shadow cells does not preclude correct diagnosis in the presence of the other relevant cytologic features. If all the major components of pilomatrixoma are present in an aspirate, the diagnosis should not be problematic. However, if one component predominates, this may lead to an erroneous diagnosis of other benign and malignant lesions.
Conclusion: Knowledge of the cytologic features of pilomatrixoma will allow correct patient diagnosis and management.