Gross and Microscopic Diagnoses in Mouse Tumors at the Site of the Mammary Glands

Abstract

Among the data reported by the Jackson Memorial Laboratory in 1933 a staff paper appeared that recorded the existence and transmission of extra-chromosomal influence affecting the incidence of spontaneous mammary tumors in mice. In one of the reciprocal outcrosses used in the above and reported in full by Murray and Little (1935 a ), the inbred parent stocks were a dilute brown strain called d, and the C57 black strain called B. Mammary tumors have been almost unknown in the B strain but the d strain has an incidence of 50 per cent mammary tumors in virgin females and about 80 per cent in the breeding females which reach the cancer age. The above outcross data were based upon the gross findings in living animals and include all tumors that by position and physical characteristics were considered to be of mammary gland origin. Nearly 100 per cent of all tumors occurring at this site in the high-mammary-tumor strain d have been either adenomata or carcinomata. Similarly situated new growths in the hybrids were naturally assumed to be tumors in which the epithelial elements were definitely the site of the most pronounced neoplastic development. The object of this paper is to discuss the types of tumors found on histological examination in the hybrids of this reciprocal outcross. In the first generation of the dB cross, with mothers from the high-cancer line and fathers from the low-cancer line, there were 113 virgin females which reached the cancer age. Of these, 45, or 39.82 per cent, developed tumors that grossly were considered to be mammary tumors. Three were lost, 41 were carcinomata, and one was an adenoma. Thus 100 per cent of the tumors that could be diagnosed histologically were of epithelial origin and 97.61 per cent were malignant.