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This report describes the organization and functions of the Registry of Experimental Cancers and gives the chronology of events that led to its establishment. Currently 21,500 accessions have been coded; the vast majority are spontaneous and induced cancers, chiefly of rodents, and also a wide variety of nonneoplastic diseases. Accessions are accepted from contributors working in laboratories in this country and abroad. The material is available for study by responsible scientists, and a limited number of study sets is available for loan on request.

Responses of strain DBAf/2 mice without the mammary tumor agent to oral administration of methylcholanthrene are reported. Mice of both sexes 2-4 months of age were given 9 weekly injections by stomach tube of 1 mg of methylcholanthrene dissolved in .2 cc of olive oil. Mammary gland tumors were induced in the females and leukemias chiefly mediastinal lymphosarcomas localized to the mediastinum were induced in both sexes. Microscopic sections from 54 of the mediastinal masses revealed 52 which were similar and were diagnosed as lymphocytic neoplasms apparently originating in the thymus. All showed the same type of neoplastic cell which had the characteristic features of malignant lymphocytes.

A classification of mouse mammary tumors in Dunn's miscellaneous group including recently reported types is presented. Adenocarcinoma type Y, first reported in (C3H X Y)F1 mice, is characterized by tubules that branch at acute angles and are lined by cuboidal epithelium. Adenocarcinoma type L is characterized by alcelike appearance and has projections of tumor cells with cytoplasmic vacuoles into lumina. Undifferentiated carcinomas in strains SWR/J and BABL/c contain sheetlike masses of epithelial cells with very little tendency to form glands but which may contain foci of cells with keratohyaline granules. Pale cell carcinomas, which occur in strain GR mice, are hormonally responsive and are characterized by the presence of pale cells and cystic spaces lined by basophilic cells. Foci of cells with acidophilic hyaline bodies and keratohyaline granules and with intercellular bridges distinguish this neoplasm from adenocarcinoma type B. A second hormonally responsive mammary tumor in strain GR mice is adenocarcinoma type P, which consists mainly of acini lined by a single layer of polyhedral cells. Carcinosarcomas of BALB/c mice have a myxoid stoma and, also containing glands, resemble mixed mammary tumors of the bitch. Criteria for differentiating trichoepitheliomas from mammary tumors are discussed.

This report covered the pathologic features, behavior, metastases, and results of transplantation of pure yolk sac carcinomas that were primary in the uterine horn of 8 mice; 6 mice were strain C3H and 2 were strain HR, and they varied from 10 to 23 months of age. Three of the mice had never been treated. Of the 5 that had, the treatment was different for each mouse. Therefore, treatment could not be correlated with tumor development. At least 5 mice were nulliparous; in fact they had never been mated, so in these some mechanism involving parthenogenesis must have been operative to account for the tumor. The tumors were identified as being primary in the uterus and occupied and distended the cavity of one uterine horn where they were polypoid or plaquelike. The neoplastic yolk cells replaced the endometrial stroma forming a support for the original endometrial glands. In time the tumor cells destroyed many of the endometrial glands. That the glands present in the primary uterine horn tumors were the original glands of the endometrium and not neoplastic glands was attested by their absence from the secondary neoplastic deposits in 4 mice in which the tumor had spread to areas outside the cavity of the uterus and from the neoplastic tissue of the tumor transplants in the recipient mice.

Enovid was administered to BALB/c mice in a liquid Metrecal diet. Experimental animals developed uterine cervical and vaginal lesions while the control groups did not develop uterine cervical or vaginal carcinomas. The experimental techniques of introducing material in a liquid Metrecal diet has many applications including the answering of some questions on dosage of estrogens and limitations of exposure time.

This study investigates genetic control over the propagation and transmission of a mammary tumor agent. Strain C3H female mice with a mammary tumor agent were outcrossed to strain C57BL males without the agent and genetically resistant to it. The female offsprings were backcrossed to strain C57BL males through 7 successive backcross generations. By the 3rd backcross generation the agent has been eliminated by concentration of strain C57BL chromatin; this suggests that strains differed by only a few genes controlling the propagation and transmission of the agent and possibly by only a single pair of genes. Females of the 7th backcross generation were then outcrossed to C3Hf males (without the agent) and their female progeny backcrossed to C3Hf males through 4 backcross generations. With the concentration of C3H chromatin the mammary tumor agent did not reappear suggesting that the concentration of C3H chromatin the mammary tumor agent did not reappear suggesting that the concentration of C57BL chromatin had eliminated the agent rather than causing it to mutate to a latent or inactive form. Mammary tumors observed at an early age in females with the tumor agent were mainly adenocarcinomas of types A and B; some of the tumors occurred in older females with or without the agent. Type C adenocarcinomas and adenoacanthomas were observed mostly in females of an advanced age both with and without the agent. It is possible that this occurrence is associated with histologic changes of the mammary gland with advancing age rather than directly related to the agents absence.