Genetics of Familial Testicular Cancer

Familial clustering of testicular germ cell tumors (TGCT) is well-documented, and a family history of TGCT is associated with an increased risk of this disease. The International Testicular Cancer Linkage Consortium (ITCLC) has assembled 350 multiple case TGCT families in support of a linkage effort that provisionally mapped a susceptibility gene to chromosome Xq27 in a subset of these kindreds. However, familial TGCT is genetically heterogeneous, thus increasing the need for meticulous case definition and classification in ongoing genetic and etiologic studies. The histopathologic classification of TGCT is very complicated; few pathologists have extensive experience reviewing this uncommon tumor. Basing epidemiologic studies upon local pathology reports may result in failure to recognize etiologically critical TGCT subsets of the kind which have been central to suspecting and defining various hereditary cancer syndromes, such as the multiple inherited renal cancer disorders.

Few studies have addressed the risk of cancer among relatives of sporadic TGCT patients. Recent reports suggest a 20% increase in overall cancer risk among first-degree relatives of TGCT patients and site-specific excess cancer risks in male relatives and in the mothers of TGCT patients. These cancer sites constitute diseases for which there is some prior evidence to suggest a genetic relationship to TGCT. Identification of other cancers as part of the familial TGCT disease spectrum would both provide clinically relevant insight into this syndrome, and enhance the statistical power of gene-seeking linkage analysis.

We propose two studies, each targeting the ITCLC set of high-risk TGCT families, none of which come from the US: (a) Centralized Pathology Review of Familial TGCT; and (b) The Occurrence of Cancer Other than Germ Cell Tumors in TGCT Families. Data will be provided by three of the largest ITCLC contributors; each will contact TGCT probands and their relatives and collect the primary data under their familial and non-familial TGCT, and perform the data analysis for both studies. NCI will neither seek nor receive individual identifying information from any participant. Currently, our UK collaborator has completed acquisition of a Federal Wide Assurance (FWA) and local ethical review. Since this group is contributing 70% of the families in these two projects, we now bring that component before the NCI Special Studies IRB. We shall return to the IRB for review of the other two contributors upon completion of their local ethical review process.

• INCLUSION CRITERIA:

The criterion establishing familial TGCT is the presence of at least two cases of documented GCT in blood relatives.

A case will be determined to have TGCT according to the following criteria:

Pathologic confirmation of a germ cell-derived tumor arising in the testis. Estragonadal sperm cell tumors will also be included.

Germ cell-derived histologies including: seminoma, embryonal carcinoma, endodermal sinus (yolk sac) tumor, gonadoblastoma, choriocarcinoma, teratoma, and mixed germ cell tumor.

A case will be determined to have TIN on the basis of pathologic confirmation of intratubular malignant germ cells (ITMGCs) as defined by Burke and Mostofi.