Hereditary breast carcinomas constitute about 10% of all malignant mammary tumors, but the selection criteria to identify a high-risk population carrying BRCA1 mutations are not yet well-defined. We have collected 51 pedigrees of familial breast cancer, 16 pedigrees of familial breast and ovarian cancer, and 30 cases of early-onset breast cancer (<35 years of age) without any family history of breast cancer. The index cases of the 97 selected families were further subdivided into three groups based on histopathological parameters: group A (n = 19) was characterized by tumor grade III, negative estrogen and progesterone receptors, and high proliferative rate; group B (n = 20) was characterized by grade I-II tumors, positive hormonal receptors, and low proliferative rate; and group C (n = 58) was not homogeneous for the histopathological criteria. The aim of our study was to evaluate, in patients with a family history of breast cancer or with early diagnosis of breast cancer, the incidence of BRCA1 mutation on the basis of tumor phenotype. We found the highest rate of BRCA1 mutations in group A (53%), and low frequencies in groups B (5%) and C (0%). Our data strongly indicate that an aggressive tumor phenotype in patients with a positive family history or early diagnosis identifies a population with high probability of carrying BRCA1 mutations. Genes Chromosomes Cancer 27:130-135, 2000.

Hereditary breast/ovarian cancer is a well-characterized clinical entity, largely attributed to the inheritance of BRCA1 or BRCA2 mutations. Among general population, the mutation's frequency of these genes is very low; therefore, the identification of two independent mutations in the same family is a rare event. This study reports the presence of two mutations, one in the BRCA1 and the second in the BRCA2 gene in an Italian Caucasian kindred. This family is composed of more than 250 individuals, spanning through five generations, among which endogamy was a common phenomenon. Considering the tumor spectrum, this family is characterized by a high incidence of different types of cancer. In our study, we considered only three out of seven family units for BRCA1 and BRCA2 analysis. In one of the family units, we found independent mutations of both BRCA genes. The BRCA1 mutation on exon 11 (3358T-A) was identified originally in the index case and subsequently in 18 members of this family, whereas the same mutation was not detected in a related family member with male breast cancer. The male breast cancer patient led to the identification, through mutational analysis, of a new BRCA2 mutation (8756delA). This BRCA2 mutation was also found in the male breast cancer patient's daughter. The discovery of the BRCA2 mutation allowed us to alert the patient's daughter who, otherwise, could be falsely reassured since she had a negative BRCA1 test.

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