Biological characteristics of two transplantable pituitary tumors of Syrian hamsters.

appear to be common in the Syrian hamster. Among thirteen spontaneous tumors occurring in one series of a thousand hamsters of unspecified age, none were of pituitary origin (1). No pituitary tumors were reported among 226 animals autop sied at the end of a normal life span, although the majority of these old hamsters had both benign and malignant neoplasms which were frequently multiple (2). One carcinoma originating in a ham ster pituitary has been reported to be in its 60th transplant generation, but information concerning its possible endocrine activity has not been pub lished (16). Although estrogens will induce pitui tary tumors in hamsters as they do in some strains