Abstract
Spontaneous vascular endothelial cell (VEC) tumors were found in 29 (14.5%) of 200 males and 30 (15.0%) of 200 females of B6C3F1 mice which had been maintained up to 109 weeks. The ages of mice with VEC tumors ranged from 72 to 109 weeks. The VEC tumors were divided into solitary and multiple types. The solitary type developed as a single, discrete lesion in the spleen of 6 males and 7 females, the liver of 8 males and 2 females, the subcutis of one male and 5 females, the parietal peritoneum of each 2 males and females, and the uterus of 3 females. The multiple type occurred in 12 males and 11 females at 2 to 5 combined sites of the spleen, liver, bone marrow, subcutis, parietal peritoneum, epididymis or thymus. There were no essential differences in histologic features and the site of neoplastic involvement between both types. Cavernous and hemangioendotheliomatous growth patterns were discerned. The former had features of cavernous hemangioma and was found in the most part of all the tumors. The latter was occasionally seen in the tumors developed in the spleen and liver, and consisted of slightly atypical cells with no dilated cavities nor mitosis. In mice with multiple VEC tumors, red blood cell count, hemoglobin concentration, hematocrit value and platelet count tended to decrease, and red blood cells with abnormal morphology were frequently seen.
