Familial double testicular tumors: identical chromosome changes in seminoma and embryonal carcinoma of the same testis.

An identical abnormal chromosome, i(12p), and a marker chromosome of unknown origin were seen in 2 tumors of different histology (seminoma and embryonal carcinoma) in the same testis. A younger brother of the patient also had undergone orchiectomy for 2 seminomas in the left testis 2 years previously. These findings are discussed in relation to the possible cellular background of testicular tumors and their genetic parameters.