Local recurrent breast cancer mimicking basal cell carcinoma and malignant melanoma

Abstract

A 52－year－old Japanese woman who underwent left mastectomy for breast cancer 13 years prior to presentation was referred to our department for evaluation of a rash on the left breast. Physical examination showed a central brown, depressed, firm, yellowish－white flat nodule (4×3 cm) at the site of the mastectomy scar, surrounded by firm yellowish－white nodules up to 1 cm in diameter. Dermoscopy revealed an atypical pigment network, blue－whitish veils, dots, globules, and arborizing vessels. Leaf－like structures and yellowish－white structureless areas were observed in the marginal region. Histopathological evaluation of a brown skin area revealed infiltration of breast tumor cells into the dermis and subcutaneous tissue with infiltration of large numbers of melanocytes and melanophages in the upper dermis. Dilated blood vessels and abundant fibrous stroma were observed in the dermis. Breast cancer that presents as a black－brown rash may show dermoscopic features of basal cell carcinoma and/or malignant melanoma.[Skin Cancer (Japan) 2024 ; 39 : 163－168]