Clinical manifestations of cutaneous metastases: a review with special emphasis on cutaneous metastases mimicking keratoacanthoma.

Approximately 5% of oncology patients develop cutaneous metastases, with only a small number of these patients (less than 1%) having metastatic skin lesions as the first sign of their visceral cancer. Metastases tend to occur on skin surfaces in the vicinity of the primary tumor. However, any site may be affected by cutaneous metastases. Skin metastases can present with several morphologies including, albeit rarely, keratoacanthoma-like lesions. Keratoacanthoma is a keratinous tumor that morphologically appears as a nodule with a central keratin-filled crater. This article reviews the characteristics of oncology patients whose cutaneous metastases mimicked a keratoacanthoma, including illustrations from our patient, a 53-year-old Caucasian man whose metastatic esophageal adenocarcinoma not only presented with a keratoacanthoma-like tumor on his upper lip but also a forehead macule and a scalp nodule. We also report keratoacanthoma-like presentations from literature cases of breast cancer, chondrosarcoma, and pulmonary malignancies. The lesions were discovered 3-24 months after diagnosis of visceral cancer and led to the discovery of unsuspected lung cancer in two patients. Most of the patients (60%) died within 2 months of discovery of the keratoacanthoma-like cutaneous metastases. We also reviewed the literature and discuss other morphologies of cutaneous metastases in patients whose primary tumors were in the breast, lung, and esophagus. In addition, we review from the literature other examples of tumors that present as metastatic nodules on the scalp. The possibility of cutaneous metastasis should be entertained and pathologic evaluation should be considered in an oncology patient with underlying visceral malignancy who develops a keratoacanthoma-like lesion.