Pilomatricoma With Florid Osseous Metaplasia: A Cytologist’s Perspective

This article presents a rare case of pilomatricoma with florid osseous metaplasia in a 32-year-old woman, highlighting the cytological and histopathological findings. Pilomatricoma is a benign skin tumor associated with hair follicle differentiation, typically affecting children and young adults. The case involved a long-standing nodule on the patient's leg, which was firm, painless, and non-progressive. Fine needle aspiration and histopathological examination revealed features such as ghost cells, calcification, and osteoclastic giant cells, with mature bony trabeculae indicating ossification. Osseous metaplasia in pilomatricoma is rare, with fewer than 15 cases reported, and is thought to result from prolonged fibroblastic response. The study suggests that bone morphogenic protein and oncostatin M may mediate the transformation of fibroblasts into osteoblasts in these tumors. The patient underwent successful surgical resection and showed no recurrence at 6 months follow-up.