Cutaneous neoplasms composed of melanoma and carcinoma: A rare but important diagnostic pitfall and review of the literature

Abstract

We report two cases of combined cutaneous tumors composed of melanoma and carcinoma. The first tumor presented as a 5-mm pink-blue macule over the right zygomatic arch in an 85-year-old man. Shave biopsy and immunohistochemical studies revealed that the tumor was composed of melanoma (highlighted by SOX10 and MART-1, with high Ki-67 proliferative index) intermixed with nodular basal cell carcinoma (highlighted by pan-cytokeratin and Ber-EP4). The neoplastic melanocytes were confined to the basal cell carcinoma nodules, and a diagnosis of combined melanoma in situ and basal cell carcinoma was rendered. After therapeutic excision, the patient was disease-free at 9 months after the initial diagnosis. The second tumor presented as a 6-mm pink-brown crusted papule on the right forehead in an 89-yearold man. Shave biopsy and immunohistochemical studies revealed that the tumor was composed of malignant melanoma (MM) (highlighted by S100 and MART-1) intermixed with squamous cell carcinoma (SCC) (highlighted by cytokeratin and p63), and a diagnosis of combined MM-SCC was rendered. These two cases highlight the importance of recognizing these rare types of melanocytic-epithelial cutaneous neoplasms to arrive at an accurate diagnosis that may inform appropriate disease stage and therapy. K E Y W O R D Sbasal cell carcinoma, combined tumors, melanoma, squamous cell carcinoma

A tale of two tumours

“…The MIS remains within the BCC and does not penetrate further Combined A neoplastic lesion containing two cell populations that are intimately admixed and are best appreciated with immunohistochemistry Biphenotypic A mixed neoplastic tumour in which both neoplastic cells originate from the same precursor stem The cells display overlapping molecular and immunohistochemical properties Table 2 Theories as to the histogenesis of bi-malignant cutaneous tumours. 1,[3][4][5] Theory Description…”

“…Bi-malignant tumours of the skin involving epidermal and melanocytic neoplastic cells are rare but well documented. [1][2][3][4][5] The most widely used classification of these lesions follows those proposed by Satter et al 1 in 2009 (Table 1). Lesions can be described as collision, combination, colonization or bi-phenotypic tumours with dual differentiation.…”