Receptor characteristics of the second tumor in synchronous versus metachronous breast cancer.

Presently, there is no consensus on whether synchronous breast cancer has the same disease origin as the primary tumor, or if it is a completely independent second primary. This study explores this concept in both synchronous and metachronous breast cancer looking specifically at their receptor characteristics and level of differentiation. A retrospective chart analysis of 114 patients with synchronous or metachronous breast cancer treated at a single institution between January 1991 and March 2004 was done. Sixty-three per cent of the patients were diagnosed with metachronous breast cancer. Synchronous breast cancer was histologically more aggressive (P < 0.05) with a significantly higher number of patients having poorly differentiated tumors, a greater number of metastases involving a larger number of organs (P < 0.05), and lower average survival compared with the metachronous group (P < 0.005). Both the first and second tumor in both groups were similar in hormone receptor status, histologic subtype, and grade. Synchronous breast cancer is more aggressive and has a poorer outcome than metachronous breast cancer. Concordance in hormone receptor status, grade, and histologic subtype between different tumors within the same patient suggests, but does not completely support, a monoclonal origin. Analysis applied here is crude and more specific methods of analysis such as DNA microarray would be required to infer such a conclusion.