Synchronous Double Malignant Tumors Consisting of Stomach and Hodgkin's Lymphoma with Collision between Gastric Adenocarcinoma and Hodgkin's Lymphoma in the Stomach

We report the rare case of a 72-year-old man with double cancers (gastric adenocarcinoma and Hodgkin's lymphoma) with collision between gastric adenocarcinoma and Hodgkin's lymphoma. Abdominal computed tomography showed increased wall thickness in the fundus region of the stomach and multiple lymph node swellings in the lesser curvature, periceliac and left cardial regions. Upper gastrointestinal endoscopy showed an ulcer approximately 5 cm in diameter with a malignant appearance in the fundus region of the stomach. On histopathologic examination, two completely different tumors were recognized in the stomach. One tumor was a poorly differentiated adenocarcinoma characterized by poorly developed tubular structures associated with prominent lymphoid infiltration of the stroma. The other tumor was found to have proliferated in the wall of the stomach, with diffuse granulomatous lesions and bordering the adenocarcinoma. Large atypical lymphoid cells with prominent nucleoli and enlarged mononuclei or multinuclei were seen in the latter tumor. Hodgkin's lymphoma was also found in the swollen lesser curvature lymph nodes. As a result, gastric adenocarcinoma and metastasis of Hodgkin's lymphoma were collided in the stomach. In conclusion, this case might be helpful in exploring the occurrence mechanism of tumor collision between lymphoma and carcinoma.