A transplantable carcinoma of the rat that originally appeared spontaneously in the mammary gland of a pregnant albino rat, and which now resembles a carcinoma in young transplants and a sarcoma in older transplants. (Stedman, 25th ed)

Synonyms: Walker Carcinosarcoma 256, Walker Carcinoma 256, Carcinosarcoma 256, Walker, Carcinoma 256, Walker