529 Original Article Rev Assoc Med Bras 2009; 55(5): 529-34 IntroductIon Breast carcinomas are considered to be a heteroge- neous group of tumors showing different behavior, prog- nosis and response to treatment. 1 Furthermore, tumors classified under the same histological type and grade can present distinct molecular aspects and biological course. The molecular heterogeneity of breast tumors cannot be morphologically assessed and it represents an important challenge for the research and treatment of breast cancer. 2 Recently, gene expression profiling (GEP) analyses using DNA microarrays and later on immunohistochemical studies using tissue microarrays (TMAs) have enabled the recognition of distinct subtypes of tumors associated with different clinical outcomes, leading to the develop- ment of a new molecular-based classification of breast carcinomas 3,5 : luminal A [positive for estrogen receptor (ER) and progesterone receptor (PR); and negative for human epidermal growth factor receptor type 2 (HER2)]; luminal B (RE+; PR+; HER2+); HER2 overexpressing (ER-; PR-; HER2+); basal-like (triple-negative; ER-; PR-; HER2-; and positive for basal cytokeratins); unclassifiable *Correspondence: Faculdade de Medicina da Universidade Federal de Minas Gerais - UFMG Departamento de Anatomia Patológica e Medicina Legal Av. Alfredo Balena, nº 190 - sala 305 Belo Horizonte - MG - Brazil CEP 30130-100 Telephone: +55 (31)34099118 - Fax: +55 (31)34099664 Email: hgobbi@medicina. ufmg.br; helenicegobbi@ gmail.com ABSTRACT objectIve. To investigate the frequency of basal-like breast cancers in a series of triple-negative tumors (TNTs), which are defned as invasive breast carcinomas negative for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor type 2 (HER2). Methods. We selected 140 previously tested TNT and analyzed their clinicopathologic characteristics and the patients’ survival rate. A tissue microarray (two cores of each tumor) was constructed and submitted to immunohistochemical stains for ER, PR, HER2, cytokeratins (CKs) 5 and 14, epidermal growth factor receptor (EGFR), p63, and p53. The ER-, PR- and HER2-negative and CK5-positive tumors were considered to have a basal phenotype (basal-like breast cancers). results. We found 105 basal-like breast cancers among the 140 TNTs (frequency = 75%). The patients’ mean age was 54.8 years old, and 34.3% of them were premenopausal women. Most tumors were classifed as high-grade invasive ductal carcinoma of no special type (NST). TNTs were positive for CK5 (75.0%), CK14 (29.0%), EGFR (36.4%), p63 (28.6%), and p53 (67.1%). Advanced cancer staging was found in 52 patients (50.0%), with tumor size larger than 5 cm in 41 cases (39.0%). Axillary metastases were detected in 61 cases (59.2%). Clinic follow-up was carried out with 89 patients (mean = 51 months). Among these, 45 patients (50.5%) had no evidence of disease; six (6.7%) were alive with the disease, and 38 (42.6%) died of cancer. Forty-two (47.1%) patients had systemic relapse, with lungs, brain and bones being the main sites of metastases. The mean overall survival was 36 months and the mean disease-free interval was 28 months. conclusIons. Our fndings confrm aggressive clinical behavior, poor prognosis, and high frequency of basal-like breast cancers amongst TNTs, similar to data previously published and in agreement with North-American and European studies. Keywords: Breast cancer. Triple-negative tumors. Basal-like phenotype. Immunohistochemistry. Survival. basal-lIke breast carcInoMas: clInIcopathologIc and evolutIve profIle MarIna de brot 1 , fernando augusto soares 2 , MônIca MarIa Ágata stIepcIch 3 , vInícIus s. cúrcIo 4 , helenIce gobbI 5* Study conducted at the Breast Pathology Laboratory, Department of Anatomic Pathology and Legal Medicine, Medical School, Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG, Brazil 1- Professora de Anatomia Patológica da Faculdade de Medicina da Universidade Federal de Minas Gerais – UFMG e Patologista do Laboratório de Anatomia Patológica e Citopatologia Pittella & Andrade, Belo Horizonte, MG 2- Professor titular da Faculdade de Odontologia da Universidade de São Paulo – FMUSP e Diretor do Departamento de Anatomia Patológica do Hospital do Câncer A.C. Camargo, São Paulo, SP 3- Patologista do Instituto Fleury, São Paulo, SP 4- Bolsista do Programa de Iniciação Científca do CNPq e aluno do curso de Medicina da Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG 5- Professora Associada da Faculdade de Medicina da Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG