Infiltrative basal cell carcinoma occurring in sites of biopsy-proven nodular basal cell carcinoma

Over 200 basal cell carcinomas (BCCs) are biopsied and subsequently excised each year at the Veterans Affairs Palo Alto Health Care System (VAPAHCS). A focal infiltrative pattern developed in the region of the biopsy scar in the re-excision specimens of 20 cases out of approximately 400 BCCs (< 5%) examined histopathologically over a 2-year period. The patient population included predominantly male, elderly Caucasians (mean age 71), and all tumors fulfilled clinical and histologic criteria for nodular BCC at the time of initial punch or shave biopsy. No patient showed recurrence of tumor following simple re-excision with 2-3 mm surgical margins, with a mean follow up of 25.4 months after excisional surgery. These neoplasms had a more benign clinical course, possibly related to scar formation in healing sites of previously biopsied nodular BCC, rather than true aggressive-growth BCC. The authors conclude that a focal infiltrative pattern in a re-excision specimen may occur histologically as a scar-induced pattern which mimics an aggressive-growth BCC, but does not appear to have the same prognosis. We believe this is an important histologic observation, as recognition of biopsy scar changes in an excisional specimen of BCC may help to distinguish it from true aggressive-growth BCC.