The metastatic capacity of multifocal breast carcinomas: extensive tumors versus tumors of limited extent.

The extent and distribution of lesions in breast carcinomas are important morphologic prognostic parameters that influence the type and results of surgical intervention, as well as the propensity for metastasis. We investigated how the extent of disease influences the risk of metastasis in a consecutive series of 519 invasive breast carcinomas that were documented in large-format histology sections. Breast carcinomas of limited extent (demonstrable invasive, in situ, and intravascular tumor structures occupied a tissue space <40 mm in the largest dimension) were delineated from extensive tumors; and the proportions of cases with lymph vessel invasion, lymph node macrometastasis, and mastectomy were registered. The risks of lymph vessel invasion and lymph node metastasis were elevated substantially for extensive multifocal invasive cancers and for multifocal tumors of limited extent compared with the risks for unifocal cancers (47%, 44%, and 21%, respectively, for lymph vessel invasion; 53%, 40%, and 20%, respectively, for lymph node metastasis). The odds ratio for having lymph node metastasis was 12.4 when extensive carcinomas with diffuse invasive component were compared with unifocal invasive tumors of limited extent. Although the risks of lymph vessel invasion and lymph node metastasis increased gradually with tumor size, they remained elevated in multifocal carcinomas in every size category. The risk of lymph node metastasis was not elevated in unifocal invasive breast carcinomas with multifocal in situ component. These results confirm that the extent and distribution of lesions in breast carcinomas are important biological prognostic factors and indicate a need for special histopathologic techniques for adequate assessment of these parameters.