Approximately 1%-4.5% of internal cancers metastasize to the skin. The most frequent primary tumors are carcinomas of the breast, stomach, lung, uterus, kidney, ovary, colon, or bladder. The lesions may represent direct extension to the skin or local or distant metastasis via lymphatic or hematogenous dissemination of tumor cells.

Cutaneous metastases usually indicate a very poor prognosis, with an approximate 75% one-year mortality rate. Patients may be any age but are typically older adults. The interval between detection of the primary tumor and development of cutaneous metastases may be on the order of years, or skin metastases may be the first manifestation of an internal malignancy.

In addition to the skin lesion(s), patients with previously undiagnosed cancer may also notice a palpable mass, pallor, or weight loss. A personal history of previous carcinoma should raise the index of suspicion for a cutaneous metastasis.

Related topic: subungual metastases