Familial testicular cancer in five members of a cancer-prone kindred.

Of a family of 13 siblings, four brothers have developed testicular neoplasms, one embryonal cell carcinoma and three testicular seminomas. A first cousin once removed on their mother's side of the family (fourth-degree relative) has developed an embryonal carcinoma. After treatment they are all alive and well. Their mother is a dizygous twin and one of ten siblings. Multiple other cancers have been diagnosed among her siblings and their offspring including breast carcinoma at age 30 years in monozygous twin nieces. Associated urogenital abnormalities, concordance of age, and discordance of pathology in the five males with testicular cancer is discussed. Further identification and reporting of this risk factor is encouraged.