552 Benign Pilomatricoma with Osseous Metaplasia: A Rare Case

Abstract Pilomatricomas are a frequently misdiagnosed benign neoplasm of the skin derived from hair matrix cells. may undergo calcification and ossification although latter is rare poorly documented, with only eight cases reported since 2006. We present case pilomatricoma osseous metaplasia arising scalp in an 87-year-old female patient. She was referred by her general practitioner via two-week pathway, for suspicious lesion. On examination, there 2×1cm nodule, protruding hardened yellow sebaceous material, on right side patient's occipital scalp. The lump hard, non-tender had been 17 years. surrounding area bleeding slightly ulcerated. A clinical diagnosis ruptured epidermal cyst made, patient prepared excision under local anaesthetic. excised lesion 23×18×10mm 22×9mm sent histology. This revealed partially ulcerated dermal composed islands keratin ‘ghost cell’ outlines. Foreign body granulomas, transition to mature lamellar bone foci were noted. There no definite populations basaloid cells features malignancy not seen. These findings consistent metaplasia. discharged 4 weeks later satisfactory wound healing. Differentiating this tumour other commonly encountered masses remains challenge, as seen which initially mis-diagnosed cyst.