Evaluation of margin status in lumpectomy specimens and residual breast carcinoma

Residual disease leads to most local recurrences, especially in those patients treated with breast-conserving therapy (BCT). This study evaluates whether assessment of excisional biopsy margins accurately predicts the presence or absence of residual tumor in the lumpectomy bed. The margin status of 201 consecutive lumpectomy specimens of 178 infiltrating and 23 in situ breast carcinomas followed by reexcision were evaluated microscopically and classified as "positive" (tumor at the inked margins), "negative" (tumor more than 0.1 cm from the inked margins), "close" (tumor within 0.1 cm of the inked margins, but not transecting it), and "indeterminate" (biopsy not inked or fragmented). Tumor size and grade were also analyzed, as potential predictors for residual disease. Residual tumor was found in 41% of the patients: in 21% of the cases with negative margins, in 63% with positive margins, in 30% with close margins, and in 56% with indeterminate margins. In 37% of the positive and 70% of the close margin cases, no tumor was found in reexcised specimens. In 24% of the cases the residual disease was composed entirely of an in situ component of the same histologic type as the initial biopsy. No relationship was found between tumor size or grade and residual disease. For breast tumors, histologically negative and "close" biopsy margins do not guarantee complete excision. A number of factors seem to be responsible for the discrepancy between the margin status and the presence/absence of residual cancer in the lumpectomy bed.