Single primary lung cancer consisting of three cancer cell types (small cell carcinoma, adenocarcinoma, and squamous cell carcinoma) in which each had metastasized to different lymph nodes.

We report a case of a 70-year-old male smoker with a single primary tumor 2.5 x 3.0 cm in size in the right lung lower lobe. A transbronchial lung biopsy revealed squamous cell carcinoma of the lung. We performed right lower lobectomy with lymph node dissection (ND2a). The resected specimen consisted of three different cell types; small cell carcinoma, adenocarcinoma and squamous cell carcinoma (in a ratio of 70: 20: 10). Each cancer cell types had metastasized to different lymph nodes. The final diagnosis was a combined small cell carcinoma in the lung. Combined small cell carcinoma is uncommon, but is nevertheless a well-described diagnostic category in lung cancers.