Aims: To examine the frequency of axillary lymph node (ALN) invasion of operable breast cancers by their combined oestrogen receptor (ER), progesterone receptor (PR) and HER-2 status.
Methods: 2227 recently operated cases in one centre were retrieved from the Multidisciplinary Breast Centre database and stratified according to their combined immunohistochemical (IHC) expression of ER/PR/HER-2 status. An equivocal HER-2 status was further analysed by Fluorescence in situ Hybridisation (FISH). The following 6 groups were considered: ER(-)PR(-)HER-2(-) (NNN; triple negative), ER(-)PR(-)HER-2(+) (NNP), ER(+)PR(-)HER-2(-) (PNN), ER(+)PR(-)HER-2(+) (PNP), ER(+)PR(+)HER-2(- )(PPN), ER(+)PR(+)HER-2(+) (PPP; triple positive). For ALN, the following variables were tested in uni- and multivariate models: age at diagnosis (years), tumour size (mm), tumour grade, ER, PR, HER-2 and the combined steroid receptor and HER-2 status. Likelihood ratio chi(2)-tests were used for univariate analysis and logistic regression for multivariate analysis.
Results: Triple positive tumours had a higher likelihood of being ALN positive than others (56.2% versus 35.7%; P<0.0001). Univariate logistic regression also withheld age, size, grade and HER-2 as predictors of ALN involvement. Final multivariate logistic regression revealed age, size, grade and PPP versus non-PPP to be independent predictors of ALN involvement; the odds ratio (OR) and 95% CI for PPP versus non-PPP tumours was 2.169 (1.490-3.156).
Conclusion: Our data provide insight into the natural history of triple positive breast carcinomas. Such tumours are more likely ALN positive than those with another steroid receptor and HER-2 status. How these findings correlate with breast cancer prognosis remains to be investigated.