Conclusion
Metachronous bilateral breast cancers, compared to synchronous bilateral breast cancers, are characterized by more aggressive phenotype, expressed by lower expression of estrogen receptor and stronger expression of cytokeratin 5/6 and vimentin; this does not, however, translate into differences in the distribution of intrinsic tumor phenotypes.
Methods
Tumor morphology and expression of 8 immunohistochemical markers were assessed in tissue microarrays containing primary breast tumor cores from 113 metachronous bilateral breast cancers and 61 synchronous bilateral breast cancers. Analyzed markers included hormone receptors (estrogen receptor, progesterone receptor), HER2, Ki67, cytokeratin 5/6, E-cadherin, vimentin and epidermal growth factor receptor. Cutoff levels are provided in the table.
Results
Metachronous bilateral breast cancers tumors had lower estrogen receptor expression (p=0.047) and higher expression of cytokeratin 5/6 (p=0.017) and of vimentin (p=0.008); in multivariate analysis only vimentin retained the significance (p=0.01). Ten (13%) and 11 (26%) of metachronous bilateral breast cancers and synchronous bilateral breast cancers had luminal A phenotype, 39 (50%) and 15 (36%) were luminal B HER2-negative, 13 (17%) and 12 (28%) - luminal B HER2-positive, 3 (4%) and 2 (5%) - HER2-positive (not luminal), and 12 (16%) and 2 (5%) had triple negative phenotype (p=0.07).