[A case of adenosquamous carcinoma at the esophagogastric junction, initially diagnosed as collision carcinoma].

A 47-year-old man was found to have a type 2 tumor of the esophagogastric junction on upper gastrointestinal endoscopy. Biopsy specimens revealed squamous cell carcinoma of the esophagus and adenocarcinoma of the stomach. The preoperative diagnosis was a collision carcinoma. No distant metastases were identified on computed tomography; therefore, partial esophagectomy and gastrectomy were performed. Pathological examination of the resected specimen revealed adenosquamous carcinoma at the esophagogastric junction (TNM classification: stage IIA, T3N0M0). Adenosquamous cell carcinoma of the esophagus and stomach is rare, but that at the esophagogastric junction even rarer.