A survey on neoplasia in domestic species over a 40-year period from 1935 to 1974 in the Republic of South Africa. II. Tumours occurring in sheep.

A survey was carried out on all ovine neoplasms recorded in the registration files of the Section of Pathology of the Veterinary Research Institute at Onderstepoort over a 40-year period from 1935 to 1974. The neoplasms were divided and tabulated into 8 groups according to body systems or tissue types. Out of a total of 673 neoplasms, 436 (64,8%) were cases of jaagsiekte (pulmonary adenomatosis). Of the remaining 237 neoplasms, 41,3% involved the skin. Eighty per cent of the cutaneous neoplasms were squamous cell carcinomas which varied from well-differentiated to anaplastic. The majority occurred on the head, in particular on the ears, frontal region and on the eyelids or nictitating membrane. Several factors have been suggested to explain the high incidence of squamous cell carcinomas on the head. Lymphosarcomas were the 3rd most commonly encountered tumours, whilst a significant number of hepatocellular carcinomas also occurred. A variety of tumours of connective tissue origin were recorded, the most common of which arose from fibrous tissue and cartilage.