Testicular germ cell tumors in HLA-genotype non-twin brothers.

The diagnosis of metastatic testicular carcinoma in a thirty-three-year-old man and his nineteen-year-old brother is reported. Histologically, the tumor of the older brother consisted predominantly of embryonal carcinoma with minor components of seminoma and adult teratoma; the tumor of the younger brother consisted entirely of embryonal carcinoma. Since previous reports suggest the possibility that the HLA genotype may be a factor in the etiology of testicular cancer, we typed the parents and four children of this family. The two affected brothers shared a paternal HLA-A3, Cw-,B7,DR2 haplotype that had not been transmitted to the two other living siblings. Analysis of the distribution of HLA haplotypes of the affected non-twin brothers of this family and those of three other non-twin pairs of brothers that have been reported showed that the affected pairs in each family shared one HLA haplotype. The differences between the expected and the observed distribution of HLA haplotypes in the four sibling pairs is not statistically significant, perhaps because of the small number of patients typed. Two of the four pairs shared a common haplotype. Additional family studies are required to establish a genetic origin of testicular tumors and to determine whether or not a "testicular carcinoma disease" gene is linked to the HLA complex. A large number of multicase families will be required for linkage analysis.