DP18 A mimicker of melanoma on sun-exposed sites

Abstract Melanocytic matricoma is a rare, benign adnexal lesion arising from the hair follicle. First described in 1999 by Carlson et al., it tends to mimic basal cell carcinoma and melanoma both clinically and histologically (Carlson JA, Healy K, Slominski A, Mihm MC Jr. Melanocytic matricoma: a report of two cases of a new entity. Am J Dermatopathol 1999; 21: 344–9). It classically presents as a dark purple–black papule on the head or neck of older patients with a history of actinic damage. It demonstrates a predilection for male patients. A biphasic tumour, it contains both epithelial and melanocytic components, with a classic histological finding of a well-circumscribed unencapsulated tumour in the superficial dermis. While it typically demonstrates benign behaviour, there have been a small number of malignant melanocytic matricomas reported. Given this potential for malignant behaviour, albeit low, current recommendations for treatment of melanocytic matricomas include complete surgical excision with clear margins and clinical follow-up. We report two cases of melanocytic matricomas with varying clinical presentation and interesting histology. In both cases, the lesions were completely excised with clear margins, and both patients have outpatient follow-up planned postoperatively. Histological analysis was vital for differentiating this tumour from other malignant pathologies it can mimic, such as melanoma and basal cell carcinoma.