Lung Cancer Presenting as Abdominal Skin Metastasis: An Unsolved Case With Extensive Literature Review

Skin metastasis is the spread of malignant cells to the skin from a primary malignancy. It is quite uncommon for skin or cutaneous metastasis of internal malignancies to manifest as an initial presentation. It occurs in about 5.3% of patients with internal malignancies, representing 2% of all skin tumors. Lung cancer (LC) has the highest incidence and is the most common cause of cancer death worldwide. Metastasis to the skin should be carefully investigated to rule out a metastatic manifestation of an occult primary site tumor. It mostly occurs late in the course of the disease and indicates a poor prognosis. We report a case of a 65-year-old male presenting with multiple abdominal skin nodules as an initial uncommon presentation of unknown primary, along with a review of the literature for which we performed a Medline search for articles on cutaneous metastases from internal malignancies, including LC, using PubMed, and a manual search of pertinent references and textbooks.