Background Pathology reports of basal cell carcinoma (BCC) biopsies often contain comments of positive or negative margins, with only 1%-2% of the margin evaluated. The negative predictive value (NPV) of biopsy margin status on residual BCC is unknown.
Objective The purpose of this study was to determine the NPV of BCC biopsy margin status on the absence of residual BCC in the corresponding excision.
Methods From our institution's archives, we collected BCC biopsies with negative margin readings that had subsequent excisions. For excisions read as negative for residual BCC, the excision blocks were sectioned at 150-μm intervals until exhausted.
Results We collected 143 cases that met criteria; 34 (24%) were found to contain residual BCC in the corresponding excision leading to a NPV of 76%; in 31 of 34 (91%) of these cases, the residual histologic subtype was superficial.
Limitations Our sectioning technique did not evaluate 100% of the excision specimens.
Conclusion Negative margins in a BCC biopsy are a poor predictor of residual disease in the patient. We recommend that clinicians treat these lesions, and that pathologists who comment on margin status of BCC biopsies consider adding a caveat to reflect these findings.