Malignant renal tumors in male hamsters (Cricetus auratus) treated with estrogen.

Received for publication, October 19, 1949. lowing: (a) 20-mg. pellets of diethylstilbestrol,1 im planted subcutaneously on the 49th or the 68th day of life, with the animals killed 90, 120, 150, 170, 180, 217, 240, 270 or 300 days later; (6) the same, except the pellets contained diethylstilbes trol and cholesterol in a ratio of 1:4 and were im planted on the 53rd day of life; (c) 0.6 mg. of di ethylstilbestrol microcrystals suspended in 0.2 cc. of saline solution or dissolved in the same amount of sesame oil, injected subcutaneously every other day, from about the 50th day of life, and continued for total periods of 90, 120, 150, 190, 210, 240 and 270 days, or from 322 to 497 days as indicated in Table 1. Kidneys from untreated male and female hamsters, ranging from 93 to 865 days in age, were examined also. Renal tumors (Fig. 1) were found in all males treated with estrogen for 250 days or longer (Table 1), except those in which diethylstilbestrol-cholesterol pellets were implanted; in these, no renal tu mors have been detected. In kidneys from two males carrying pellets of pure diethylstilbestrol for 217 days, numerous, small, adenomatous nodules were observed microscopically, but not grossly. No renal tumors have been observed in any female, in any untreated male, in any treated, castrated male, or in any control treated with sesame oil or with saline solution. The tumors have always occurred bilaterally. They are usually adenomatous in character and always cortical in location. Tumor masses fre quently appear as well defined but never encapsu lated, more or less rounded, solid nodules of vary ing size (Fig. 2). They are often cystic and some times hemorrhagic (Fig. 3); they have not been ob served to ulcerate. As a rule, the epithelium con sists of small more or less cuboidal cells, rather embryonal in appearance, arranged in branching and anastomosing cords. The tumor cells contain a sudanophilic, singly refractive lipid; they frequently resemble small