Combined malignant melanoma and basal cell carcinoma tumor of the intermingled type

The combination of malignant melanoma (MM) and basal cell carcinoma (BCC) within a single tumor is an unusual finding.

An 84-year-old white man with a pigmented tumor on the back showing a combination of MM and BCC.

A 1.5 x 1.5-cm irregular brown lesion on the back was clinically suggestive of MM. Histopathologically, the lesions turned out to be a combined tumor consisting of a superficial BCC and a regressive MM with a tumor thickness of 1.25 mm. The conglomerates of the BCC lay within the MM and were admixed with a high number of Melan-A-positive melanocytic cells.

By reviewing the low number of published cases, we found that a combined MM-BCC tumor exists in two variants: a collision type in which components of each cell type are clearly demarcated and an intermingled type in which both cell types grow intimately together. Although both types occur as a mere incidence, in particular, the intermingled type may be diagnostically challenging and the evaluation of its dignity may be questionable.