Synchronous and metachronous primary gastric lymphoma and adenocarcinoma: a clinicopathological study of 12 patients

BACKGROUND: The occurrence of both malignant gastric lymphoma and adenocarcinoma in the same patient is very rare. METHODS: The resected specimens from 12 patients who had both primary gastric lymphoma and adenocarcinoma were analyzed using immunohistochemistry and in situ hybridization. RESULTS: Two different tumors were found synchronously in 10 patients (5 with independent tumors and 5 with contiguous/collision tumors) and metachronously in 2. The size of the lymphomas (mean, 7.2 cm) was larger than that of the adenocarcinomas (mean, 3.6 cm) (P < 0.005). Histologically, 9 of the 12 lymphomas (75%) were mucosa-associated lymphoid tissue lymphomas, and all lymphomas invaded the deep portion of the submucosa or deeper. Conversely, 10 of the 12 adenocarcinomas (83%) were early carcinomas. Six adenocarcinomas were intestinal type, whereas the other 6 were diffuse type. The MIB-1 index of the adenocarcinomas (mean, 50.4%) was higher than that of the lymphomas (mean, 29.3%) (P < 0.05). Helicobacter pylori (H. pylori) was documented in all 12 patients, whereas Epstein-Barr virus-encoded RNA 1 was detected in only 2. During the follow-up period after surgery, 6 patients died, 4 due to adenocarcinoma. The survival probability of all 12 patients appeared to be similar to that of previously reported patients with gastric adenocarcinoma alone, and was significantly worse than that of the 217 patients with gastric lymphoma alone (P < 0.05). CONCLUSIONS: An H. pylori infection is considered to be associated with the development of these double malignancies. In many such synchronously observed cases, lymphomas may precede carcinogenesis, while the prognosis appears to be more closely associated with the adenocarcinoma than the lymphoma.