title: Sporadic invasive breast carcinomas with medullary features display a basal-like phenotype: an immunohistochemical and gene amplification study.
abstract: It is not clear whether invasive breast carcinomas with medullary features (IBCMFs, atypical medullary carcinomas) constitute a specific phenotype of breast cancer that is of biologic significance. Because medullary features are common in BRCA1-associated carcinomas and these tumors frequently show a basal-like phenotype, we examined whether IBCMFs expressed basal/myoepithelial markers and had a basal-like phenotype. We studied the immunohistochemical expression of 15 markers in tissue microarrays containing samples from 35 IBCMFs and 39 grade 3 invasive ductal carcinomas (IDCG3s) of no special type. In addition, we analyzed EGFR, C-MYC, and CCNE gene amplification by fluorescence in situ hybridization, because the expression of these genes is known to be associated with the basal-like phenotype. We defined the basal-like phenotype according to the criteria of Nielsen et al as being those tumors that were ER/HER2-negative and cytokeratin (CK) 5/6- and/or epidermal growth factor receptor-positive. IBCMFs were more frequently hormone receptor- and HER2-negative, but had greater expression of proliferation markers and p53. In addition, IBCMFs more frequently expressed basal/myoepithelial markers, such as CK5/6 and P-cadherin. A basal-like phenotype was found in 62.9% of IBCMFs but in only 18.9% of IDCG3s. No differences in gene amplification were found between IBCMFs and IDCG3s, although C-MYC amplification was more common in tumors without a basal-like phenotype. The identification of IBCMF as an independent group of tumors could be of clinical significance, given the high incidence of cases with a basal-like phenotype, which is a group of tumors with different prognosis and chemotherapy response from those of IDCG3s of no special type.
authors.affiliation: Breast and Gynecological Cancer Group, Molecular Pathology Programme, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain.
authors.forename: Socorro María
authors.initials: SM
authors.lastname: Rodríguez-Pinilla
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Rodríguez-Gil
authors.forename: Gema
authors.initials: G
authors.lastname: Moreno-Bueno
authors.forename: David
authors.initials: D
authors.lastname: Sarrió
authors.forename: M Del Carmen
authors.initials: Mdel C
authors.lastname: Martín-Guijarro
authors.forename: Lucía
authors.initials: L
authors.lastname: Hernandez
authors.forename: José
authors.initials: J
authors.lastname: Palacios
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D018276:Carcinoma, Medullary / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019927:Cyclin E / Q000235:genetics; D005260:Female; D005784:Gene Amplification; D018773:Genes, erbB-1; D016259:Genes, myc; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D046888:Tissue Array Analysis
chemical_list: D014408:Biomarkers, Tumor; D019927:Cyclin E