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Aims: To characterize clinico-pathological features and clinical outcome of low grade triple negative early breast carcinomas. Material and methods: Between January 2005 and December 2006, 300 tumours were classified as triple negative (ER-ve, PR-ve, HER2 0/1+) out of 3000 patients treated for a breast cancer at the Institut curie. Patients with a low-grade (grade 1 and 2 according to Ellis and Elston) T1 and small T2 (< 3cm) breast carcinoma treated with surgery first were considered in our study. Immunohistochemistry was performed with ER, PR, Androgen Receptor (AR), HER2, Ki67, EGFR, CK5/6, CK14 and CK8/18 antibodies for all tumours; GCDFP15 for invasive lobular carcinomas (ILC) and invasive ductal carcinoma (IDC) with apocrine features, and CA15-3 to assess the inverted polarity if needed. Results: We identified 36 low-grade carcinomas out of 186 triple negative breast carcinomas (19%). Thirty-two tumours were grade 2 and four tumours grade 1 and associated with a low or a moderate mitotic score. Ki67 proliferation index was high (20%) in 22 cases (61 %) (median: 22%-mean: 29%). Thirty-one (86%) tumours showed a basal-like phenotype (EGFR+ or CK5/6+ or CK14 +). Interestingly, the five "nul" (non basal-like) triple negative tumours demonstrated a low proliferation index (Ki67 20%). All but one tumors expressed CK8/18. The tumour's size varied between 3 and 37 mm (mean = 17.2). Lympho- vascular invasion was present in 10 cases (27%). High and intermediate grade ductal carcinoma in situ component was associated in 28 cases (77%). Stroma was abundant and associated with a lymphocytic infiltrate in all cases. Various histological types were observed: 16 IDC (44%), 7 ILC (19%), 5 IDC with apocrine differentiation, 2 micropapillary, 1 papillary, 1 mucinous, 3 adenoid cystic and one low grade adeno-squamous carcinomas. Three out of 16 IDC showed a week nuclear positivity with AR. Five and six out of the seven ILC were positive for AR and GCDFP15 respectively. All carcinomas with apocrine differentiation were AR and CGDFP15 positive. Conversely, all micropapillary, papillary and mucinous carcinomas were AR negative. The mean age of patients was 61.6 years. Distant metastases occurred in five patients. Thirty-three (91 %) women were alive and 29 (80%) of them without evidence of cancer at 6 years of follow-up. Conclusion: Low grade invasive carcinomas represent 19% of the cases in our series of 186 triple negative early breast carcinomas and were diagnosed in patients older than 60 years. These cases were of various histological types, were all associated with a marked lymphocytic infiltrate and in the majority of the cases with high grade ductal carcinomas in situ. Despite a low mitotic activity, proliferation index was generally higher than 20% except for "nul" non-basal cases. However, patient's overall survival seemed to be better than that reported for high grade triple negative breast cancer. Histological types, proliferation and age should be taken into account for treatment decision in triple negative early breast carcinoma patients. [ABSTRACT FROM AUTHOR]