Background: Spreading of carcinoma has been considered to be a prognostic factor for local failure after breast-conserving therapy. The extensive intraductal component (EIC) was defined as when the component of intraductal carcinoma constitutes more than 25% of the primary tumor with intraductal foci. However, the definition of EIC was based on the predominance of intraductal component surrounding the invasive lesions and not on the segmental anatomy. We designated carcinoma extension as the intraductal spread of carcinoma (ISC) along with the duct-lobular system by three-dimensional (3-D) reconstruction analysis. This study was initiated to simplify the method of two-dimensional (2-D) pathological examination based on 3-D mapping. Methods: Thirty-four specimens from breast cancer patients were subjected to 3-D reconstruction. We investigated the correlation between actual extension of intraductal carcinoma and EIC defined by 2-D examination or ISC grading defined by 3-D reconstruction. Furthermore, using another 62 histological mappings, we investigated how correctly the simplified 2-D method using several paraffin blocks reflected the actual carcinoma spread and margin state. Results: Carcinoma extension over 2 cm was observed in 64% specimens that were EIC positive and 26% specimens that were EIC negative. In contrast, according to the ISC grading defined by 3-D reconstruction, none of the specimens with a low grade of ISC demonstrated carcinoma extension over 2 cm. Carcinoma extension over 2 cm was observed in 71% of specimens with a high grade of ISC, thus demonstrating a correlation between carcinoma extension and ISC grading. In addition, the simplified 2-D method using only several blocks reflected both the 3-D ISC grading and surgical margin state. Conclusions: We conclude that ISC grading correlates with carcinoma extension and surgical margin state. From a clinical point of view, the simplified 2-D examination using paraffin blocks may contribute to routine surgical pathology in evaluating the degree of carcinoma extension in breast-conserving therapy.
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