MORPHOLOGY OF SPONTANEOUS HARDERIAN-GLAND TUMORS IN AGED B6C3F1 MICE

Spontaneous Harderian gland tumors in B6C3F1 mice were found in 18(3.1 %)(one male had bilateral tumors) of 589 males and 18 (3.0%) of 609 fe males. The tumor-bearing mice ranged in age from 73 to 109 weeks. Thes e tumors comprised 32 adenomas (86.5%), four adenocarcinomas (10.8%) a nd one pleomorphic tumor (2.7%); the adenomas were classified, basesd on the growth patterns, into 17 papillary, nine cystic papillary, five acinar and one cystic types. Two adenocarcinomas grew papillary and i nvaded surrounding tissues, and the other two grew acinously. The pleo morphic tumor consisted of pleomorphic cells some of which had a kerat in-positive epithelial feature and acini lined by atypical epithelial cells.