Occult lung cancer incidentally found during surgery for esophageal and gastric cancer: a case report.

A 70-year-old male was admitted to our hospital because of advanced esophageal squamous cell carcinoma and early gastric adenocarcinoma. A esophagectomy and partial gastrectomy with three-field lymph node dissection (neck, mediastinum and abdomen) was performed. Both tumors had lymph node metastases. In addition, three mediastinal lymph nodes (two subcarinal lymph nodes and a middle thoracic paraesophageal lymph node) were involved with adenocarcinoma. To elucidate whether they were metastases from the gastric cancer, an immunohistochemical analysis was performed. The cancer cells in these lymph nodes were positive for cytokeratin (CK) 7 and negative for CK 20, thus suggesting metastasis from a nondigestive organ. Interestingly, they were positive for thyroid transcription factor 1 (TTF-1), indicating metastasis from a lung cancer. Since the preoperative computed tomographic scan showed no evidence of lung cancer, a diagnosis of metastases from an occult lung cancer was finally recorded. Ten months after surgery, the patient was alive without a recurrence or the appearance of a lung cancer.