Basal cell carcinoma (BCC) is the most common type of skin cancer frequently encountered in both dermatology and primary care settings.1 When biopsies of these neoplasms are performed to confirm the diagnosis, pathology reports may indicate positive or negative margin status. No guidelines exist for reporting biopsy margin status for BCC, resulting in varied reporting practices among dermatopathologists. Furthermore, the terminology used to describe margin status can be ambiguous and differs among pathologists; language such as “approaches the margin” or “margins appear free” may be used, with nonuniform interpretation between pathologists and providers, leading to variability in patient management.2
When interpreting a negative margin status on a pathology report, one must question if the BCC extends beyond the margin in unexamined sections of the specimen, which could be the result of an irregular tumor growth pattern or tissue processing. It has been estimated that less than 2% of the peripheral surgical margin is ultimately examined when serial cross-sections are prepared histologically (the bread loaf technique). However, this estimation would depend on several variables, including the number and thickness of sections and the amount of tissue discarded during processing.3 Importantly, reports of a false-negative margin could lead both the clinician and patient to believe that the neoplasm has been completely removed, which could have serious consequences.
Our study sought to determine the reliability of negative biopsy margin status for BCC. We examined BCC biopsy specimens initially determined to have uninvolved margins on routine tissue processing and determined the proportion with truly negative margins after complete tissue block sectioning of the initial biopsy specimen. We felt this technique was a more accurate measurement of true margin status than examination of a re-excision specimen. We also identified any factors that were predictive of positive true margins.
We conducted a retrospective study evaluating tissue samples collected at Geisinger Health System (Danville, Pennsylvania) from January to December 2016. Specimens were queried via the electronic database system at our institution (CoPath). We included BCC biopsy specimens with negative histologic margins on initial assessment that subsequently had block exhaust levels routinely ordered. These levels are cut every 100 to 150 µm, generating approximately 8 glass slides. We excluded all tumors that did not fit these criteria as well as those in patients younger than 18 years. Data collection was performed utilizing specimen pathology reports in addition to the note from the corresponding clinician office visit from the institution’s electronic medical record (Epic). Appropriate statistical calculations were performed. This study was approved by an institutional review board at our institution, which is required for all research involving human participants. This served to ensure the proper review and storage of patients’ protected health information.