Melanocytic matricoma: an additional case with literature review over this rare entity

 Melanocytic matricoma is a rare cutaneous adnexal tumour first described as a distinct entity in 1999 by Carlson et al. It commonly presents as a well circumscribed pigmented dermal nodule, frequently on sun-damaged skin of elderly men. Melanocytic matricoma is presumed to recapitulate the growth of anagen hairs.   A 36-year old female presented to the clinic with an 18-month history of a non-tender solitary darkly pigmented lobulated nodule on the right parietal scalp. The nodule was surgically excised. Histopathology showed a well-circumscribed nodular dermal lesion, consisting of a mixed population of basaloid, intermediate and shadow cells admixed with dendritic melanocytes. Immunohistochemical studies were negative for Ber - EP4 while positive for S100, Beta Catenin and E – Cadherin. Based on the clinical, microscopic and immunohistochemical findings, a diagnosis of melanocytic matricoma was made.   To date, there have been only 16 cases reported in the literature. We report an additional case of melanocytic matricoma with similar clinical and histopathological findings to previously described cases. To the best of our knowledge, this is the first case reported in a middle aged female in the Middle East. It's important to recognize this neoplasm as it should be considered in the differential diagnosis of tumours that present with a dual cell population of follicular and matrical differentiation. Long-term follow-up is indicated to exclude the aggressive potential of these matrical neoplasms.