Four primary malignant neoplasms in a single patient.

A 60-year-old Caucasian male, with a previous history of a 10-year occupational exposure to ionizing radiation, chemical carcinogens, and a long history of tobacco and alcohol abuse, developed synchronous squamous cell carcinoma of the floor of the mouth and adenocarcinoma of the lung. Four years later, squamous cell carcinoma of the larynx followed by squamous cell carcinoma of the tongue were diagnosed. In this case report, we suggest that increased exposure to multiple carcinogenic factors may result in an increased incidence of both synchronous and metachronous primary malignant neoplasms.