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Frequent Development of Pancreatic Carcinomas in the Rana nigromaculata Group¹

Department of Pathology, Cancer Institute, Kami-Ikebukuro, Toshima-ku, Tokyo 170 [P. M., Y. K., K. N., H. S., T. K.]; Laboratory for Amphibian Biology, Faculty of Science, Hiroshima University, Higashihiroshima 724 [M. N., H. U.]; and Mitsui Memorial Hospital, Kandaizumi-cho, Chiyoda-ku, Tokyo 101 [I. Y.], Japan

In 1979, 2 species of pond frogs (Rana nigromaculata and Rana plancyi plancyi) were imported from China, and hybrids were made between these and Japanese, Korean, and Taiwanese pond frogs (R. nigromaculata, Rana plancyi fukienensis and Rana brevipoda) that had been kept for a number of years in the Laboratory for Amphibian Biology of Hiroshima University. From 1982, development of tumors, especially in the peritoneal cavity, was noticed frequently in the hybrids and also later, although rarely, in the Japanese pond frogs. Such tumors had never previously been observed among pond frogs in the laboratory.

Histological and immunohistochemical studies identified the i.p. tumors to be pancreatic carcinomas with occasional production of insulin and/or somatostatin. Ultrastructural investigation revealed both endocrine and exocrine secretion granules together with C-type retrovirus particles in the carcinoma cells. Other tumors included a retroperitoneal rhabdomyosarcoma, liver adenomas, and an unclassifiable mesenchymal tumor of the foot pad.

¹ Supported in part by grants-in-aid from the Ministry of Education, Science and Culture, Japan.

² To whom requests for reprints should be addressed.

Received 4/21/95. Accepted 7/ 6/95.

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