LISBON – Two of 10 nonmelanoma skin cancers are misdiagnosed as being of a nonaggressive tumor subtype at initial biopsy, according to Dr. Nathalie Zeitouni.
This raises concern that a substantial number of biopsied squamous and basal cell carcinomas are being treated suboptimally, Dr. Zeitouni said at the congress.
She presented a consecutive series of 513 patients referred for Mohs micrographic surgery for biopsy-proven BCC or SCC. Based upon routine Mohs intraoperative evaluation of all histologic tumor layers, 21.1% of the cancers were of aggressive subtypes that went undiagnosed on initial biopsy.
Aggressive subtypes of nonmelanoma skin cancer include basosquamous carcinoma, invasive SCC, and morpheaform, infiltrating, keratinizing, and micronodular BCC. Nonaggressive subtypes include follicular, nodular, adenoid cystic, and superficial BCC, as well as SCC in situ, according to Dr. Zeitouni, chief of dermatologic surgery at the Roswell Park Cancer Institute, Buffalo, N.Y.
In only 51% of cases was there concordance between the preoperative and the definitive intraoperative diagnosis of a nonmelanoma skin cancer as being of an aggressive or nonaggressive subtype.
In 21% of cases the intraoperative evaluation showed no residual tumor present, only scar. In 5.5% of cases, intraoperative histologic tumor layer evaluation resulted in downgrading of the nonmelanoma skin cancer from an aggressive to a nonaggressive subtype.
Dr. Zeitouni stressed that dermatologists need to have a low threshold for suspecting that a nonmelanoma skin cancer is of an undiagnosed aggressive subtype. If the lesion is clinically atypical or it responds poorly to standard excision or simple destructive measures, that possibility becomes distinctly more likely. Aggressive subtypes, she added, are best managed by Mohs surgery.
She said she had no relevant financial disclosures.