Epidermotropically metastatic malignant melanoma. Differentiating malignant melanoma metastatic to the epidermis from malignant melanoma primary in the epidermis.

In four instances, metastases to epidermis from primary cutaneous malignant melanomas at different sites showed histological features similar to those of cutaneous malignant melanoma primary in the epidermis. In these metastases, atypical melanocytes were present within the epidermis and in the upper part of the dermis much as in primary cutaneous malignant melanoma. Therefore, the presence of atypical melanocytes within the epidermis is not in itself an absolute criterion of malignant melanoma primary in skin. Nor does that finding absolutely deny malignant melanoma metastastic to the skin. Features that may enable histologic differentiation of epidermotropically metastatic malignant melanoma from primary cutaneous malignant melanoma are emphasized.