Superficial basal cell carcinoma, think deeper: Step sectioning of skin biopsy specimens yields 14% more aggressive subtypes

Because of different therapeutic regimens for superficial and non-superficial basal cell carcinomas (BCCs), accurate histopathological examination of a punch biopsy to determine its subtype is essential. The aim of the current study was to evaluate the additional yield of a more extensive step-section method to that of a standard histologic examination at 4 levels. Data for this prospective study was obtained from the Pathology department of a Dutch tertiary hospital. Biopsy specimens of subsequent patients from March 2019 to June 2020 were sectioned to 8-levels instead of the regular 4-levels. Only patients with a superficial BCC subtype in the first 4-levels of sectioning were included (n = 100). After 8-level sectioning, it was recorded in which level (5-8) a more aggressive BCC component was found (i.e. nodular, infiltrative, or micronodular). Patients were followed-up to evaluate further treatment, and in case of excision, the excision specimen was reviewed to determine the BCC subtype. A logistic regression was performed to assess characteristics associated with a more aggressive BCC component in levels 5-8. In 14 patients (14%) a more aggressive component was found in levels 5-8, all with a nodular component. Thirteen of these patients underwent excision, confirming a more aggressive BCC subtype. Of the 86 patients that had no deeper BCC component in levels 5-8, 26 (30.2%) underwent excision; In 4 patients no residual BCC was found, in 15 patients superficial BCC, and in 7 a more aggressive BCC subtype (1 nodular and 6 a combination of superficial/nodular/infiltrative). In multivariable analysis, head&neck localization was associated with finding a more aggressive BCC subtype in levels 5-8 (OR 6.41 (95%CI 1.56-26.30), p = 0.01)). More extensive sectioning of superficial BCC biopsy specimens, especially in the head&neck area, leads to a more accurate BCC subtype diagnosis requiring different clinical management strategies.