Metastatic squamous cell carcinoma presenting as an erythematous nodule in a man with lung adenocarcinoma.

Skin metastases from visceral malignancies have been well documented in the literature, and may be the presenting sign of an occult internal malignancy. Lung cancer in particular is a relatively common cause of skin metastases, which are considered a poor prognostic sign. Rarely, patients with lung cancer develop a second primary lung cancer that may require a novel chemotherapeutic regimen. The frequency of second primary malignancies presenting with metastatic skin lesions is not documented in the literature. We present a case of a 50-year-old man with a history of metastatic lung adenocarcinoma who was referred for evaluation of a nodule overlying his right mandible, which had been progressively enlarging for two weeks. Biopsy demonstrated metastatic squamous cell carcinoma. Subsequent CT-guided biopsy of a left retroperitoneal lymph node was conducted and notable for squamous cell carcinoma. Therefore, this patient's skin lesion was the presenting sign of a second primary visceral tumor, likely originating in the lung. We present this case to raise clinical awareness of the rare phenomenon that cutaneous metastasis may be the first sign of a visceral cancer, even in the setting of a previous distinct primary malignancy.