Transplantation characteristics, morphologic features, and interpretation of preputial gland neoplasia in the Fischer 344 rat.

Preputial gland neoplasms in the Fischer 344 rat are relatively uncommon tumors with a prevalence of approximately 3% in the National Toxicology Program data base. They occur late in life, are well differentiated, and rarely metastasize. Based on studies through 4 serial passages, 10 well-differentiated preputial gland neoplasms transplanted into the mammary fat pads of syngeneic recipients grew to 30 mm within 10 weeks. Recipients died or were sacrificed with large transplanted tumors within 6 months. The morphologic features of the transplanted neoplasms were similar to those of the primary neoplasms through the four passages. Proliferative lesions of the preputial glands comprise a morphological continuum and separation of these growths into categories of hyperplasia, adenoma, and carcinomas is based largely on cytological features and the degree of altered growth patterns. Morphologic features to assist in diagnosis of preputial gland neoplasms and recommendations for interpreting treatment-associated increases of these neoplasms are presented.