Malignant lymphomas arising in Peyer's patches and other organs of untreated NZO-Bl mice.

Summary The pathology of all types of lymphoreticular cancers in untreated NZO/Bl mice of the original colonies is presented. Overall, there were 37/451 (8.2%) animals with malignant lymphomas, 50% of the tumors primary in Peyer9s patches of the intestine. Peyer9s patch lymphomas spread to other abdominal lymphatic organs but did not involve the liver or extend beyond the abdomen, as did cytologically similar tumors primary in other sites. Cytological classification of the primary lymphomas showed 59% overall were of mixed cell type, 18% histiocytic type, and 10% lymphocytic type. Of the Peyer9s patch lymphomas, 78% were of mixed cell type and the remainder were histiocytic. The sex incidence of lymphomas was equal, but lymphomas of lymphocytic type were found only in females and occurred late in life. The anatomic pattern of lymphoma metastasis resembled that for other types of cancer with direct extension, regional, and distant metastasis; there were only 2 cases with leukemia-like disease. The possible significance of Peyer9s patch lymphomas for etiological studies is noted.