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An immunohistological study using a Leu 7 antibody, which is a marker for human NK and K cells, was carried out in two cases of gastric carcinomas with prominent reactive hyperplasia. The patients were a 72-year-old man and a 55-year-old man who had shown good postoperative courses in spite of the advanced stage of their tumors. There were many scattered Leu 7 positive cells in the lymphoid hyperplasia, predominantly in the germinal centers and the peri-follicles. The number of Leu 7 positive cells were even more pronounced in a patient whose condition was more advanced. These findings suggest that lymphoid hyperplasia, particularly with regard to the NK and K cell response, plays a significant role in the clinical benignity of the tumors.

This report deals with a histologic demonstration of a combined tumor of early signet ring cell carcinoma and lymphoma of the stomach in a 52-year-old Japanese man. The Gastric carcinoma was found by a systemic work up for a tonsillar lymphoma. The relationship between the malignant lymphomas of the stomach and of the tonsil is not clear in this case. The carcinoma and lymphoma of the stomach were both small, and the depth of invasion was localized to the mucosa and submucosa, respectively. The lymphoma was observed just beneath the cancer and was a diffuse, large cell type, and of the same histologic typing as the tonsillar lymphoma. Based on the broader size of the carcinoma, it is considered that the carcinoma probably induced the lymphoma in the stomach. This of an early combined tumor of carcinoma and lymphoma of the stomach is, to our knowledge, the first to be reported in the literature.

Two cases of an undifferentiated carcinoma of the stomach have been investigated by conventional histologic, immunohistochemical, and ultrastructural methods. The patients were a 73-year-old man and 65-year-old man. A postoperative histological examination of the resected stomach of each patient disclosed large areas of an undifferentiated carcinoma which were relatively well demarcated from areas of the adenocarcinoma. In the undifferentiated carcinomatous areas, the reticulin fiber stain was epithelial in pattern, and mucin staining proved negative. Similarly both Grimelius and Fontana-Masson staining also negative. In like manner immunostains using cytokeratin , vimentin , IgG, IgA, s-100 protein, and NSE were all negative, and an electron microscopic study showed no neurosecretory granules or mucin secretory granules. Based on these findings, the diagnosis of either a malignant lymphoma or small cell anaplastic carcinoma could be excluded, and thus an undifferentiated carcinoma was the determination.