Pilomatricoma: A Case Series Highlighting Cytological Diagnostic Pitfalls

Pilomatricoma (PMX) is an uncommon benign skin adnexal tumor that frequently poses diagnostic challenges on fine-needle aspiration cytology (FNAC) due to its variable morphological spectrum. We present six histologically confirmed cases of PMX from our institution, emphasizing the cytological diagnostic pitfalls. The series included three females and three males (age range: 28-52 years) presenting with subcutaneous nodules at various locations. Clinical diagnoses include lipoma, sebaceous cyst, and tuberculosis. Correct cytological diagnosis was achieved in four cases (66.7%), while two cases were misdiagnosed as metastatic adenocarcinoma and small round cell tumor due to focal sampling and predominance of basaloid cells. All cases were confirmed as PMX on histopathology with uneventful follow-up. This series highlights the importance of recognizing the dual cell population (ghost cells and basaloid cells), performing multiple needle passes from different sites, and awareness of cytological mimickers to avoid misdiagnosis. PMX should always be considered in the differential diagnosis when primitive-appearing cells are aspirated from subcutaneous nodules, particularly to prevent unnecessary aggressive workup for malignancy.