Tumours in Iceland. 3. Malignant tumours of kidney. A histological classification.

Malignant tumours of the kidney occurring in Iceland during the years 1955 - 1974 were studied pathologically and typed histologically according to a classification proposed, but not yet published, by the World Health Organisation. Histological material was available from 89.2% and 84.0% of registered male and female patients respectively. Among males, renal cell carcinomas constituted 91.8%, transitional pelvic carcinomas 5.5% and nephroblastomas 2.7% of classified tumours. The corresponding figures for females were renal cell carcinomas 96.7%, transitional pelvic carcinomas 0.8%, and nephroblastomas 2.5%. The most frequent cell type of renal cell carcinoma group in both sexes was the combination of clear and granular cells, and the most frequent architecture was the combination of solid and tubular patterns. Renal cell carcinomas composed of pure granular cells were found in 22% of males and in 14% of females, and granular cells in combinations with all other cell types were also more common in males. In Iceland renal cell carcinoma is the fifth commonest malignant tumour in males and the tenth in females. The excess of granular cell tumours among males corresponds roughly to, and may account for, the sex difference in the frequency of renal cell carcinomas.