Need for consensus in diagnostic practices for actinic keratoses, squamous cell carcinoma

Due to the lack of clarity in literature, widespread implementation of consensus recommendations for actinic keratoses and cutaneous squamous cell carcinoma is needed, according to a study.

Actinic keratoses (AK), cutaneous squamous cell carcinoma (cSCC) in situ and invasive cSCC have “considerable variation in descriptions in the literature,” according to Rachel E. Christensen, BS, of the department of dermatology at Northwestern University Feinberg School of Medicine in Chicago, and colleagues.

“Moreover, there is a lack of consensus regarding key histopathologic features and their relationship to disease prognosis,” the researchers wrote. “This potentially complicates clinicians’ ability to understand diagnostic nuance and select appropriate treatment.”

In this literature review and cross-sectional multi-round Delphi process involving international dermatopathologists, Christensen and colleagues identified the points of widespread agreement and “grey areas in which agreement was absent” in diagnosing AK and cSCC in order to develop a consensus criteria.

In the Delphi surveys, 15 dermatopathologists voted on statements to which they agreed or disagreed in regard to diagnosing AK and cSCC. The statements were refined to reflect a consensus, defined as 70% of the panel being in “strong” agreement.

Results showed that the panel agreed on key dermatopathologic features for diagnosing cSCC and AK, including the grading of degree of cellular differentiation in cSCC and utility of immunohistochemistry for diagnosis of cSCC. There was also a widespread consensus on pathologic features that should be reported for cSCC and AK.

While the panel agreed on most standards, there were several controversial topics where consensus was not achieved. The panelists disagreed as to the definition of “Bowenoid” AK and how to approach treatment. Additionally, they could not reach a consensus on whether basosquamous carcinoma represents a more aggressive variant than either basal cell carcinoma or cSCC. The appropriateness of in-office cytokeratin pan monoclonal antibody immunostaining at the time of Mohs surgery or complete circumferential peripheral and deep margin assessment to confirm negative margins was also disputed.

While it was preferred that cSCC differentiations be grouped into two categories rather than three, the panel could not agree on which categories should be collapsed.

Many panel members expressed varying reasons for their preferences of certain immunohistochemical stains in identifying poorly differentiated SCC. There was consensus that immunohistochemical staining with cytokeratin 5, AE1/3, p63 and p40 were the best differentiators. Although half of the panel agreed staining with p40 was best, consensus was not quite reached.

Lastly, 64% of panelists strongly agreed that keratoacanthoma was a variant of well-differentiated cutaneous SCC, whereas 21% strongly disagreed, demonstrating that this category remains particularly elusive, according to the researchers.

“Consensus regarding the clinical and histopathologic features and reporting of AK and cSCC may improve communication among pathologists as well as between pathologists and clinicians, facilitating future research regarding diagnosis and management,” Christensen and colleagues wrote.