Cancerous residue in breast‐conserving surgery

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Abstract
Local tumor extension was studied using a continuous series of multiple blocks of mastectomy specimens to assess malignancy remaining after breast‐conserving surgery for early‐stage breast cancer. In this study, 183 cases were chosen, consisting of 6 noninvasive ductal carcinoma cases and 177 invasive ductal carcinoma cases. The histopathology in 59 (32%) of the 183 cases corresponded to that showing extensions of more than 2.6 cm from the tumor margin. These wide extensions were also seen in 17% of breast cancers with a tumor size of less than 2 cm. The incidence of wide extension was higher in younger patients with cases of noninvasive ductal carcinoma. Extension to the nipple‐areola was seen in 14% of cases with a tumor size of less than 2 cm. Breast cancers with multicentric development accounted for 3% of those with a tumor size under 2 cm. These findings suggest that if lumpectomy is performed with a margin of 2 cm for tumors with a size of 2 cm or less, a cancerous residue would be found in the surgical margin of 15–20% of the cases. The actual incidence was 23% of cases after breast‐conserving treatment in our study. On the basis of the data, breast‐conserving treatment with only local resection of the primary lesion showed cancerous residue such as intraductal cancerous extension in about 20% of cases. Therefore, it was concluded that, as part of breast‐conserving therapy of early‐stage breast cancer, radiation therapy of the whole breast should be performed after surgery with clear margins to Control local recurrence.