Medscape: Dermatologic Manifestations of Metastatic Carcinoma of the Skin

"Cutaneous metastasis is a rare occurrence but may be the presenting sign of a primary internal malignancy."

"The most common sources of cutaneous metastases in woman are the breasts (69%), the colon (9%), melanoma (5%), the ovaries (4%), and the lungs (4%). In men, they are the lungs (24%), the colon (19%), melanoma (13%), and the oral cavity (12%)."