Molecular characterization of breast cancer in young Brazilian women.
OBJECTIVE
To evaluate the distribution of molecular subtypes of breast tumors diagnosed in young Brazilian women and to analyze the frequency of loss of heterozygocity (LOH) in BRCA1 among different molecular subtypes of early-onset breast cancer.


METHODS
Samples from 72 cases of invasive breast carcinoma diagnosed in women aged between 19 and 40 years were evaluated using an immunohistochemical panel of biomarkers. Three intragenic BRCA1 locus microsatellites, D17S1322, D17S1323, and D17S855, were PCR amplified from matched normal (lymphocyte) and tumor DNAs for (LOH) analysis.


RESULTS
We found 13 cases (18%) that had an immunohistochemical profile consistent with being basal-like. Forty cases (55%) were luminal A type; 11% (8 cases) were luminal B type, 13% (9 cases) were HER2-overexpressing tumors and two cases were ER-/HER2- carcinomas lacking basal marker expression. Four of the 16 informative cases at D17S1322, one of the four informative cases at D17S855, and none of the five informative cases at D17S1323 displayed LOH (four basal-like and one Luminal A). Microsatellite instability (MSI) at D17S855 and D17S1322 was found in two cases (one a basal-like and one Luminal A).


CONCLUSIONS
In our study, basal-like tumor was the second most frequent molecular type among young Brazilian women and was only observed in women diagnosed under the age of 35 years. There was no significant difference of LOH at BRCA1 locus rates between basal-like breast tumors and not-basal-like breast tumors (p=0.62). LOH in BRCA1 and MSI in these breast cancers were not frequent but may indicate a small group of breast cancers with a specific molecular makeup.
Carvalho
Leda Viegas de
LV
Curso de Medicina, Centro Universitário Lusíada, UNILUS.
Pereira
Emílio Marcelo
EM
Frappart
Lucien
L
Boniol
Mathieu
M
Bernardo
Wanderley Marques
WM
Tarricone
Vicente
V
Tavtigian
Sean
S
Southey
Melissa Caroline
MC
D000328:Adult; D014408:Biomarkers, Tumor / Q000097:blood; D001938:Brazil; D001943:Breast Neoplasms / Q000235:genetics*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics*; D016009:Chi-Square Distribution; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D019398:Genes, BRCA1; D006801:Humans; D019656:Loss of Heterozygosity / Q000235:genetics*; D053842:Microsatellite Instability; D018295:Neoplasms, Basal Cell / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*; D055815:Young Adult
D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases