Background: Contralateral breast cancer is either a metastatic lesion or the second primary cancer. From biological and therapeutic viewpoints, it is important to differentiate metastatic lesions from second primary cancer in bilateral breast cancer.
Methods: Based on Chaudary's histological criteria, we analysed the tumors in 14 and 27 patients with synchronous and metachronous bilateral breast cancers with full histological and biological evaluations. The Nottingham combined histological grade and immunohistochemistry (IHC) for the estrogen receptor, progesterone receptor and cerbB-2 were used.
Results: The median age of the patients at first diagnosis was 41 years (range, 26-68 years) and the median time interval between first and second tumors was 34 months (range; 7-209 months) in metachronous cancers. The histopathological type was found in 93% of synchronous cancers and 59% of metachronous cancers (P = 0.02). The concordance rates of T stage and TNM stage were 71 and 64% respectively in synchronous cancers, while they were 24 and 32% respectively in metachronous cancers (P = 0.03). For progesterone receptor status, the concordance rates were 86 and 52% in synchronous and metachronous cancers respectively (P = 0.03). In addition, there was no statistically significant difference in terms of N stage, histological grade, intraductal component, estrogen receptor status, or cerbB-2 expression.
Conclusion: In spite of the limitation of Chaudary's criteria and the number of patients involved, the combination of histopathological type, T stage and TNM stage shows that synchronous cancers are closer to same clonal lesions (metastatic lesions) than metachronous cancers and that a biomarker, such as progesterone receptor status, plays a role in addition to the histological parameters in differentiating metastatic cancers from second primary cancers.