Albergaria et al. BMC Cancer 2011, 11:299 http://www.biomedcentral.com/1471-2407/11/299 findings concerning histological grade and tumour size were found [53]. Interestingly, we found no difference regarding lymph node metastization between luminal, HER2-overexpressing tumours and TNBC. Thus, although it has been suggested that TNBC tend to disse- minate in a lower frequency to lymph nodes, we found that 51.4% of TNBC developed metastasis to lymph nodes. This percentage shows that 1) the lymph node involvement in TNBC is as frequent as in other sub- types of breast cancer and, 2) the extension of this involvement do not differ between breast tumour sub- types. In the last 4 years, interesting studies have reported data concerning positive lymph node status in TNBC compared to non-TNBC, describing percentages of positive lymph nodes in TNBC ranging from 42.5% [55] to 54.4% [40], therefore, corroborating the results presented herein. Based on that, and even considering some putatively less prominent lymph node involvement in TNBC, which accordingly to our results was not observed, tumour size and grade variables are someway playing a compensatory score augmentation to NPI algo- rithm. Additionally, survival curves concerning tumour size and lymph node status demonstrated that these prognostic factors are equally important to stratify survi- val outcomes in non-TNBC as in TNBC. Taken together, and considering that the majority of TNBC lesions are grade III, these largely studied prognostic factors are reli- able to be used in the assessment of NPI in TNBC. Inter- estingly, we also found a slight association between tumour size and lymph node status in TNBC. This result contributes to some controversy concerning the existence or not of a relationship between size and lymph node sta- tus, since some authors already argued a lack of associa- tion between these two prognostic factors in TNBC [40]. In our TNBC series, we have a proportion of 74% of BBC. The discrepancies about the association between tumour size and lymph node status could be explained if the TNBC cohort used by Dent et al. were enriched in basal-like breast tumours compared with the cohort we studied here. These hypothesis lay on a robust study recently published by Ellis group, where although a trend (non-significant) to display lymph node involvement with increasing tumour size was seen (especially in tumours larger than 4 cm), basal-like tumours do not seem to obey the “size-node” rule [56]. Conclusions While basal-like tumours is a designation only revealed by gene profiling signatures [6], TNBC is a clinico- pathological classification which identifies a group of breast cancer with aggressive behaviour [2,38], and where improvements on therapy development and prog- nostication are compulsory. In the study presented Page 8 of 10 herein, we demonstrated that besides the fact that TNBC disseminate to axillary lymph nodes as frequently as luminal or HER2 tumours, we also showed that TNBC are larger in size compared with other subtypes and almost all grade III, therefore making truthful, at a clinical standpoint, the applicability of NPI as a prog- nostic tool in TNBC. Additional material Additional file 1: Association of tumour size (A), histological grade (B) and lymph node status (C) to high scores of NPI in TNBC. The boxplot graphic show an association between larger tumours, displaying high histological grade and with extensive lymph node invasion, with tumours clustered into the worst outcome group, represented by NPI > 5.4 (p < 0.0001) (A, B and C). The graphic highlights the contribution of lymph node status to the augmentation of NPI, showing that LNS is a determinant factor to predict worse prognosis in TNBC patients. Acknowledgements and Funding Authors would like to thank to Catarina Pereira by the effort and dedication in retrieving and organizing the breast cancer samples for this work. This work was supported by research grants from FCT - Foundation for Science and Technology [grant number SFRH/BPD/73247/2010 to A.A]. This work was also supported by a research project from Institute of Molecular Pathology and Immunology of Porto University (IPATIMUP), Porto, Portugal. IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology and Higher Education and is partially supported by FCT. Author details 1Institute of Molecular Pathology and Immunology of Porto University (IPATIMUP), Porto, Portugal. 2Institute of Biomedical Sciences of Abel Salazar (ICBAS), Porto, Portugal. 3Department of Pathology of Hospital of Divino Espírito Santo, Ponta Delgada, Portugal. 4Department of Pathology, Medical Faculty of University of Porto, Alameda Prof. Hernâni Monteiro, Porto, Portugal. 5Federal University of Santa Catarina, Florianopolis, Brazil. 6Department of Pathology, Hospital Xeral-Cíes, Vigo, Spain. Authors’ contributions AA carried out all the statistical studies, participated in the coordination of the study, intellectual content and drafted the manuscript. SR participated Pathologists VC, IA, DV, FM and JCT helped in the acquisition of data and evaluated the results of the clinic-pathological analysis. SR and FM were involved in critical revising and for important intellectual content. JCT and FS participate in the design of the study and coordination of the manuscript. 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