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Papillary lesions of the breast are a heterogeneous group of diseases characterised by the presence epithelial proliferation supported by fibrovascular stalks. Normal breast tissue does not show papillary morphology and the mechanisms underlying papillary morphogenesis in breast tumours remain poorly understood. Current clinical evidence indicates an indolent behaviour of malignant papillary breast tumours. Herein, we present some phenotypic features that may explain the development of papillary morphology of breast lesions. Active papillary morphogenesis, which appears to reflect a unique mechanism involving interaction between epithelial and mesenchymal elements, is best appreciated in intraductal papilloma and papillary carcinoma. Morphological evidence suggests papillary morphogenesis during oncogenesis is a dynamic process with variable degrees of papillary differentiation among the same lesion and between primary and metastatic tumours. Secondary papillary-like architecture of non-papillary breast lesions exists. Further studies of the molecular mechanisms underlying papillary morphogenesis in the breast and its association with a better outcome are warranted., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

It is often difficult to make a definitive diagnosis of papillary breast lesions using core needle biopsy (CNB) specimens. We studied loss of heterozygosity (LOH) on chromosome 16q in order to assess its diagnostic use for papillary breast lesions in CNB specimens. Of 25 patients with intraductal papillary breast tumors, we extracted DNA from paired samples of tumor cells from CNB specimens and non-tumor cells from subsequent excision specimens and analyzed LOH at the D16S419 and D16S514 loci on chromosome 16q. LOH analysis results were compared with final diagnoses based on pathological features of the resected specimens. On the CNB specimens, 21 tumors were histologically diagnosed as indeterminate or suspicious for malignancy, while four tumors were unambiguously malignant. Of the 21 indeterminate or suspicious tumors, 11 were finally diagnosed as benign and ten as malignant, and on these, LOH analyses were informative for 8 of the 11 benign tumors and 7 of the 10 malignant tumors. LOH was also informative on two of the four tumors unambiguously malignant on CNB. None of the eight informative benign tumors showed LOH on 16q. Six of the eleven informative malignant tumors showed LOH on 16q. LOH on 16q was significantly different between CNB specimens of benign and malignant intraductal papillary tumors (P = 0.007). Analysis of LOH on 16q may be helpful in making a definitive diagnosis in cases of papillary breast lesions, in both excised and CNB specimens.

Introduction: Breast papillary lesions represent a heterogeneous group of tumors ranging from benign to malignant, including several intermediate forms. Malignant papillary tumors are rare and their molecular characterization is still limited. A few studies pointed to the presence of specific genetic alterations that could be relevant both for diagnostic purposes and to elucidate tumour development and progression. In order to look into the issue, we compared LOH relative frequencies of four microsatellite markers located on chromosome 16 in a set of morphologically different papillary breast lesions. LOH at TP53 locus was also analyzed throughout lesions., Materials and Methods: Fifteen cases were analyzed. Sections including a malignant papillary lesion, a benign lesion (when available), and normal breast tissue were selected. Fifteen malignant and twelve benign areas were microdissected using the Leica laser microdissection system (AS LMD). After DNA extraction samples were tested for the following markers: TP53, D16S423, D16S310, DS163210 and D16S476, and analyzed on ABI PRISM 3100 (Applied Biosystems, Foster city CA)., Results: Fourteen malignant lesions and twelve paired benign areas appeared to be informative for at least one of the four markers on chromosome 16. In particular, LOH at loci 16p13 and 16q21 was detected in both benign and malignant lesions, whereas LOH at locus 16q23 was limited to malignant lesions. Nine malignant and seven benign lesions were informative for LOH at TP53 locus, that was found to be significantly associated (p=0.01) with the malignant phenotype., Conclusions: Our data suggest an involvement of chromosome 16 mutations in the early steps of breast papillary tumorigenesis. TP53 deletion and possibly LOH at 16q23 appear to play a role as progression factors, being they significantly associated with malignant transformation of breast papilloma.

Papillary carcinoma of the breast is a variant of predominantly intraductal carcinoma characterized by a papillary growth pattern with fibrovascular support. Loss of heterozygosity (LOH) was evaluated at multiple chromosomal loci (including loci reported to show frequent genetic alterations in breast cancer) to determine the frequency of genetic mutations in these tumors and their precursors. Thirty-three papillary lesions of the breast (6 papillary carcinomas, 12 carcinomas arising in a papilloma, and 15 intraductal papillomas with florid epithelial hyperplasia) were retrieved from the files of the Armed Forces Institute of Pathology (AFIP). Tumor cells and normal tissue were microdissected in each case and screened for LOH at INT-2 and p53 as well as several loci on chromosome 16p13 in the TSC2/PKD1 gene region (D16S423, D16S663, D16S665). LOH on chromosome 16p13 was present in 10 of 16 (63%) informative cases of either papillary carcinoma or carcinoma arising in a papilloma as well as in 6 of 10 (60%) informative cases of intraductal papilloma with florid epithelial hyperplasia (IDH). One case showed simultaneous LOH in both the florid IDH and carcinoma components of a papilloma. LOH was not observed at either INT-2 or p53 in any of the papillary carcinomas or papillomas with florid IDH. In conclusion, a high frequency of LOH at chromosome 16p13 (the TSC2/PKD1 gene region) is in both papillary carcinomas of the breast as well as in papillomas with florid IDH, including a case with LOH present simultaneously in both components. These findings suggest that chromosome 16p contains a tumor suppressor gene that frequently is mutated early in papillary neoplasia.