Cytogenetic changes in benign proliferative and nonproliferative lesions of the breast

Genomic Changes in Normal Breast Tissue in Women at Normal Risk or at High Risk for Breast Cancer

Sporadic breast cancer develops through the accumulation of molecular abnormalities in normal breast tissue, resulting from exposure to estrogens and other carcinogens beginning at adolescence and continuing throughout life. These molecular changes may take a variety of forms, including numerical and structural chromosomal abnormalities, epigenetic changes, and gene expression alterations. To characterize these abnormalities, a review of the literature has been conducted to define the molecular changes in each of the above major genomic categories in normal breast tissue considered to be either at normal risk or at high risk for sporadic breast cancer. This review indicates that normal risk breast tissues (such as reduction mammoplasty) contain evidence of early breast carcinogenesis including loss of heterozygosity, DNA methylation of tumor suppressor and other genes, and telomere shortening. In normal tissues at high risk for breast cancer (such as normal breast tissue adjacent to breast cancer or the contralateral breast), these changes persist, and are increased and accompanied by aneuploidy, increased genomic instability, a wide range of gene expression differences, development of large cancerized fields, and increased proliferation. These changes are consistent with early and long-standing exposure to carcinogens, especially estrogens. A model for the breast carcinogenic pathway in normal risk and high-risk breast tissues is proposed. These findings should clarify our understanding of breast carcinogenesis in normal breast tissue and promote development of improved methods for risk assessment and breast cancer prevention in women.

Obesity is associated with atypia in breast ductal lavage of women with proliferative breast disease

BACKGROUND

Benign proliferative breast disease without atypia slightly increases breast cancer risk but there are currently few clinical options for breast cancer prevention in this group of women.

METHODS

We conducted a pilot study of women with a past diagnosis of proliferative breast disease with a goal to determine if the characteristics of cells obtained by breast ductal lavage were related to nutritional factors.

RESULTS

There were 57 women who enrolled. A total of 39 women yielded nipple aspirate fluid (NAF) samples and 36 underwent breast ductal lavage. Five of the lavage samples were acellular and 28 had at least 200 cells. Surprisingly, atypia was present in 11 women. Presence of atypia was associated with slight changes in morphometric features of the epithelial cells such as measures of circularity as obtained by image analysis, but the only variable significantly different in women with atypia (versus no atypia) was a higher mean body mass index. Body mass index was also significantly correlated with C-reactive protein (CRP) levels in the nipple aspirate fluid, indicating that obesity might have a pro-inflammatory effect on the breast that can contribute to increased rates of atypia.

CONCLUSIONS

Although the clinical significance of atypia in breast ductal lavage is uncertain, these results support further work on prevention of obesity as a strategy for reducing breast cancer risk.

Chromosomal rearrangement as the basis for human tumourigenesis

PURPOSE

To develop a model for the initiation of human tumourigenesis that is consistent with various observations that are difficult to reconcile with current models.

CONCLUSIONS

A novel model of tumourigenesis was developed that includes three basic postulates: (1) tumourigenesis is initiated by recombinogenic DNA lesions, (2) potentially recombinogenic DNA lesions in transcribed regions of the genome can be converted into chromosomal rearrangements and (3) chromosomal rearrangements alone are insufficient for tumourigenesis but can initiate a mutator/recombinator phenotype.

Molecular study of clonality in multifocal and bilateral breast tumors

The clonal origin of multiple tumors in the same individual has long been debated. The main aim of this study is to find out whether multiple tumors in same individuals originated from a single clone. In our previous work (Pathol. Res. Pract. 199 (2003) 313-321), the deletion at chromosome1p36 was found to occur early because of common allelic loss in the bilateral tumors. In order to further investigate the findings about the clonality of tumors, eight tumors from four patients (two synchronous bilateral breast carcinoma [biBC], one case with breast carcinoma in one breast and multiple calcified fibroadenoma nodules in another breast, and one case with multifocal fibroadenosis in one breast) were subjected to polymerase chain reaction (PCR) to detect (a) loss of heterozygosity (LOH) and microsatellite size alterations (MA) using microsatellite markers distributed over five chromosomal arms 11p/q, 13q and 17p/q, and (b) Cyclin D1 amplification. Some markers were intragenic for BRCA1, BRCA2, BRCAX, ATM, TP53, and RB1. Although a few cases were studied, our findings suggest that in at least a proportion of patients multiple tumors may arise from a single clone.

Cytogenetic findings in phyllodes tumor and fibroadenomas of the breast

The cytogenetic data on fibroadenomas and cystosarcoma phyllodes tumor of the breast, which are both biphasic breast tumors composed of epithelial and stromal components, are quite limited. In this study, we report on clonal chromosomal alterations in three fibroadenomas and one cystosarcoma phyllodes analyzed by GTG banding. The fibroadenomas presented mostly numerical abnormalities involving chromosomes 16, 18, and 21. One case presented a deletion on 17p. The cystosarcoma phyllodes presented numerous numerical abnormalities, mostly chromosome gains, and several marker chromosomes.

Cytogenetic changes in nonmalignant breast tissue

Cytogenetic changes are common in breast cancer and have also been described in fibroadenomas and fibrocystic disease, but not in histologically normal breast tissue. Cytogenetic analysis was performed on nonmalignant breast tissue from benign breast lumps (n = 8), reduction mammoplasties (n = 31), and grossly nontumorous tissue from cancerous breasts (n = 84), using standard techniques and G-banding. All samples were reviewed histologically. Clonal chromosomal changes were found in three of eight benign breast tumors (38%). Of the reduction mammoplasties, 17 samples contained nonproliferative changes, and three of these (18%) showed a clonal deletion of 3p. No pathology was identified in the other 14 samples, of which one (7%) contained two clonal changes, apparently balanced translocations. Of nontumorous tissues from cancerous breasts, 15 (18%) showed clonal chromosomal abnormalities. Five of these samples were histologically normal. Two clones were identical to those found in the corresponding cancer. In 18 additional samples, single cells were detected with the same change as that seen in clones or single cells in the cancer. Only 4 of these 20 samples contained detectable cancer cells. Clonal abnormalities found in two or more samples included trisomies X, 7, and 20 and monosomies 19 and 18. Clonal changes were not significantly more frequent in proliferative than in nonproliferative lesions. The Icelandic BRCA2 founder mutation, 999del5, was detected in four samples, all histologically normal, two of which had clonal chromosomal abnormalities. In conclusion, clonal chromosomal changes are not infrequent in nonmalignant breast tissue and can be detected even in the absence of histological abnormalities.

Chromosome analysis in 31 cases of benign and malignant breast tumors: a study in Brazil

Cultures of 31 breast tumors, being 20 carcinomas and 11 benign lesions, were cytogenetically analysed. Clonal chromosome aberrations were detected in 16 carcinomas and in 4 benign lesions. Nine carcinomas and 2 benign lesions had multiple cytogenetically unrelated and related clones, whereas a single abnormal clone was observed in 7 carcinomas and in 2 benign lesions. Polyploid clones were found in 7 carcinomas and in 2 benign lesions. The presence of clonal chromosome aberrations and polyploid cells was not associated with the clinicopathologic parameters tested. Carcinomas had more clonal changes than benign lesions (p = 0.031), showing that cytogenetic features are of diagnostic value and that different chromosome anomalies might have different pathogenetic and prognostic significance.

Clonal rearrangement of 15p11.2, 16p11.2, and 16p13.3 in a case of nodular fasciitis: additional evidence favoring nodular fasciitis as a benign neoplasm and not a reactive tumefaction

This article describes a case of nodular fasciitis with the karyotype 47,XY,+4/46,XY,add(15)(p11.2), t(16;16)(p13.3;p11.2). The presence of clonal chromosomal abnormalities in this case, as well as in three previously reported cases, indicates that nodular fasciitis is a benign neoplasm and not a reactive lesion.

Loss of heterozygosity in benign breast epithelium in relation to breast cancer risk

The multistage model of breast carcinogenesis suggests that errors in DNA replication and repair generate diversity in the breast epithelium (the mutator phenotype), resulting in selection and expansion of premalignant clones with an acquired survival advantage. We measured loss of heterozygosity (LOH) in breast epithelial cells obtained by random fine-needle aspiration (FNA) biopsy from 30 asymptomatic women whose risk of breast cancer had been defined by the Gail model. Polymorphic microsatellite markers were selected on the basis of their relevance to breast cancer. Breast epithelium of 11 (37%) of 30 women had normal cytology, and that of 19 (63%) had proliferative cytology (eight with atypia and 11 without atypia). LOH was detected in two women with normal cytology and in 14 women (seven with atypia and seven without atypia) with proliferative cytology (P =.007). The frequency of LOH was associated with the cytological diagnosis, as well. The mean proportion (range) of informative markers demonstrating LOH was 0.02 (0-0.20) for the 11 women with normal cytology, as compared with 0.15 (0-0.50) for the 19 women with proliferative cytology (P =.02). Mean lifetime risk for developing breast cancer, as calculated by the Gail model, was 16.7% for women with no LOH compared with 22.9% for women with any LOH (P =.05). These observations support a multistage model of breast carcinogenesis where the initiating events are those that result in genomic instability. Accurate individualized breast cancer risk assessment may be possible based on molecular analysis of breast epithelial cells obtained by random FNA.

Cytogenetics of benign breast lesions

This review summarizes the cytogenetic information on benign breast lesions of various histologies, i.e., fibrocystic lesions from women with and without a known hereditary predisposition to breast cancer, fibroadenomas, phyllodes tumors, and papillomas, and relate the chromosomal features with those in breast carcinoma. In general, the frequency of chromosome abnormalities is lower in benign lesions than in breast cancer, and seems to correlate with the histologic features of the tissue, and the corresponding risk of developing invasive mammary carcinoma; aberrations are more common in proliferative than in nonproliferative lesions. The karyotypes are generally less complex than those detected in invasive carcinoma, and more often involve balanced rearrangements. No lesion-specific aberration has so far been detected; on the contrary, changes repeatedly encountered in breast cancer samples can be found in benign lesions as well, e.g., gain of 1q, interstitial deletion of 3p, and trisomies 7, 18, and 20. Especially intriguing is the prevalence of rearrangements of the short arm of chromosome 3, with the minimally deleted bands 3p13-14, in proliferative lesions from prophylactic mastectomies in breast cancer families. The potential tumor suppressor gene(s) in this region remains, however, to be identified.