(CANCER RESEARCH 31, 953—956,July 1971] SUMMARY Histological examination of an invasive neoplasm from an 18-month-old female domestic shorthair cat revealed it to be a pleomorphic fibrosarcoma that ranged in microscopic appearance from well-differentiated collagenous connective tissue to anaplastic sarcomatous

Histological examination of an invasive neoplasm from an 18-month-old female domestic shorthair cat revealed it to be a pleomorphic fibrosarcoma that ranged in microscopic appearance from well-differentiated collagenous connective tissue to anaplastic sarcomatous tissue that infiltrated surrounding musculature and skin. The fibrosarcoma was transmitted by whole cells or cell-free preparations to 8 to 10 neonatal kittens. The original neoplasm and the induced fibrosarcomas that were examined electron microscopically contained mature and budding C-type particles. Immunodiffusion studies with serum prepared in rabbits against purified ether-disrupted feline leukemia virus revealed identity between the feline leukemia virus group-specific antigen and extracts of the original fibrosarcoma.