Chromophobe Adenoma-Like Lesions of the Rat Hypophysis Frequency of the Spontaneous Lesions and Characteristics of Growth of Homologous Intraocular Transplants*

In a study of spontaneous diseases that occur in albino rats with advance in age, chromophobe adenoma-like lesions were found in the bypophyses of many old rats of the Yale strain. The frequency of this lesion in a limited series of animals, and the prel iminary results of intraocular transplantation of one of the lesions, have been reported (8). Periods of 7 to 12 months elapsed before growth of these transplants became evident, and it was therefore thought likely that advanced age of the host was necessary for growth of this type of tissue following transplantation. This is contrary to the usual experience that transplanted tumors grow best in young animals, and would suggest that this tissue had little if any autonomy of growth and therefore was not neoplastic. Experiments have been continued to determine so far as possible by the behavior of transplants whether the spontaneous growths represent hyperplasia of chromophobe cells in response to endogenous stimuli associated with advancing age, or true neoplasia in the generally accepted sense. The experiments were designed to study the character of growth of transplants under varying conditions of age, sex, and strain of the hosts. For comparison, transplants were made of normal hypophyseal tissue. The study of frequency of the spontaneous lesions has been continued to include a larger number of rats of the Yale strain. In addition, the pituitaries of rats of the Sherman strain and of a stock derived from the Wistar albino strain have been examined.