Lineage-restricted chromosome translocation in a benign fibrous tumor of the breast

Lack of DNA copy number alterations revealed with comparative genomic hybridization in fibroadenomas of the breast

There are very few studies reporting DNA copy number changes in fibroadenomas of the breast. Using comparative genomic hybridization, we analyzed 20 paraffin-embedded samples of fibroadenomas of the breast from patients with no familial or previous history of breast cancer. No alterations in the DNA copy number were observed in any of the tumors analyzed, regardless of the chromosomal alterations observed using conventional cytogenetic analysis. We discuss our results and compare them to other reports on fibroadenomas.

Clonal chromosomal alterations in fibroadenomas of the breast

A cytogenetic study on short-term cell cultures from 10 fibroadenomas of the breast is reported. Clonal chromosomal alterations were observed in all cases analyzed, involving preferentially chromosomes X, 12, 14, 20, and 22. Normal karyotypes were found in 34.9% of the cells. The present findings are discussed together with the reports on fibroadenomas and other benign lesions of the breast described in the literature. Although no specific chromosome abnormality to date can be attributed to a particular type of benign breast pathology, some recurrent alterations are starting to emerge and may characterize these benign breast lesions, differentiating them from their malignant counterparts.

Cytogenetic description of breast fibroadenomas: alterations related solely to proliferation?

Twelve breast fibroadenomas were analyzed cytogenetically and only four were found to have clonal alterations. The presence of chromosomal alterations in fibroadenomas must be the consequence of the proliferating process and must not be related to the etiology of this type of lesion. In contrast, the few fibroadenomas that exhibit chromosomal alterations are likely to be those presenting a risk of neoplastic transformation. Clonal numerical alterations involved chromosomes 8, 18, 19, and 21. Of the chromosomal alterations found in the present study, only monosomy of chromosomes 19 and 21 has been reported in breast fibroadenomas. The loss of chromosome 21 was the most frequent alteration found in our sample. The study of benign proliferations and their comparison with chromosome alterations in their malignant counterparts ought to result in a better understanding of the genes acting on cell proliferation alone, and of the genes that cause these cells to exhibit varied behaviors such as recurrences, spontaneous regression and fast growth.

Fibrous tumor of the breast in a postmenopausal woman receiving estrogen

Fibrous tumor of the breast is a rare, benign stromal proliferation with atrophy of the epithelial component. Almost all patients who develop fibrous tumors are premenopausal. An unusual example of fibrous tumor of the breast is reported in a 62-year-old postmenopausal woman. The mass, first noted 1 year previously, progressively enlarged over the year. The patient noted a history of taking exogenous estrogens for 10 years. Intense estrogen administration during the year of enlargement may be associated with accelerated growth of the tumor. In addition, positive nuclear staining for estrogen receptor antibodies in stromal cells was demonstrated by immunohistochemical methods.

Comparative genomic hybridization detects novel amplifications in fibroadenomas of the breast

Comparative genomic hybridization analysis was performed for identification of chromosomal imbalances in 23 samples of fibroadenomas of the breast. Chromosomal gains rather than losses were a feature of these lesions. Only two cases with a familial and/or previous history of breast lesions had gain of 1q or 16q as the sole abnormality. The most frequently overrepresented segments were 5p14 (10/23 cases), 5q34-qter (6/23 cases), 13q32-qter (6/23 cases), 10q25-qter (5/23 cases), and 18q22 (4/23 cases). Some of these regions have previously been associated with breast carcinoma, but this study indicates that gain of these regions can also occur in benign breast lesions. Our findings may provide a basis for conducting further investigations to locate and identify genes associated with proliferation that may be involved in the early steps of tumorigenesis of the breast.

The clonal origin and clonal evolution of epithelial tumours

While the origin of tumours, whether from one cell or many, has been a source of fascination for experimental oncologists for some time, in recent years there has been a veritable explosion of information about the clonal architecture of tumours and their antecedents, stimulated, in the main, by the ready accessibility of new molecular techniques. While most of these new results have apparently confirmed the monoclonal origin of human epithelial (and other) tumours, there are a significant number of studies in which this conclusion just cannot be made. Moreover, analysis of many articles show that the potential impact of such considerations as patch size and clonal evolution on determinations of clonality have largely been ignored, with the result that a number of these studies are confounded. However, the clonal architecture of preneoplastic lesions provide some interesting insights --many lesions which might have been hitherto regarded as hyperplasias are apparently clonal in derivation. If this is indeed true, it calls into some question our hopeful corollary that a monoclonal origin presages a neoplastic habitus. Finally, it is clear, for many reasons, that methods of analysis which involve the disaggregation of tissues, albeit microdissected, are far from ideal and we should be putting more effort into techniques where the clonal architecture of normal tissues, preneoplastic and preinvasive lesions and their derivative tumours can be directly visualized in situ.

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.

Two cases of fibrocystic breast disease with polysomy 18 as the sole clonal cytogenetic abnormality

In the present study, we describe the occurrence of numerical alterations of chromosome 18 in two cases of benign fibrous/fibrocystic tumors of the breast, both of which were studied by conventional cytogenetic investigations and one of which was additionally tested by fluorescence in situ hybridization with the use of an alphoid centromeric probe specific for chromosome 18. Case 1 showed a tetrasomy 18 in 2 of 33 metaphases as the only clonal chromosomal aberration. Case 2 revealed both trisomy and tetrasomy 18 as clonal alterations in metaphases and interphase nuclei.

Karyotypic abnormalities in fibroadenomas of the breast

Short-term cultures of 50 fibroadenomas of the breast were cytogenetically analyzed. Nine tumors were found to display clonal chromosome aberrations. One had multiple, cytogenetically unrelated clones, whereas the others had a single abnormal clone each. Four cases had one balanced translocation as the sole anomaly, and one had a complex intrachromosomal rearrangement of chromosome 3, leading to loss of 3p material. One fibroadenoma had a single numerical aberration, and one had supernumerary ring chromosomes. The remaining 2 cases had both numerical and structural aberrations. The only recurrent alterations were trisomy 20 and rearrangement of chromosome arm 1p. The finding of similar chromosomal aberrations in fibroadenomas and carcinomas suggests that women with karyotypically abnormal fibroadenomas may have an increased risk of developing subsequent breast cancer. If so, different chromosome anomalies might have different pathogenetic and/or prognostic significance.