Locations and types of neoplasms in immature dogs: 69 cases (1964-1989).

Sites, histologic types, and frequencies of neoplasms in immature dogs (less than or equal to 6 months old) were evaluated from data collected over 25 years. The frequencies of neoplasms in immature dogs were compared with those of mature dogs (greater than 6 months old). Of 69 immature dogs with neoplasms, 5 had 2 primary neoplasms each, resulting in a total of 74 neoplasms. The 3 most common sites for neoplasia, in decreasing order, were the hematopoietic system, brain, and skin. Immature dogs were 10.9 times more likely to have a neoplasm located in the brain, compared with mature dogs. Immature dogs also were 3.3 times more likely to have a neoplasm associated with the hematopoietic system, compared with mature dogs.