Diagnostic concordance among dermatopathologists using a three-tiered keratinocytic intraepithelial neoplasia grading scheme.

The distinction between actinic keratosis (AK) and squamous cell carcinoma in-situ (SCCIS) is a subject of discussion among dermatopathologists. A previous study determined that there was excellent interobserver agreement among dermatopathologists using the current two-tiered grading system. Presently, we assessed concordance among dermatopathologists using a three-tiered keratinocytic intraepithelial neoplasia (KIN) diagnostic system. At the 2006 meeting of the American Society of Dermatopathology (ASDP), registration personnel solicited 125 registrants by randomly inserting an invitation into 125 registration packets. Participants reviewed 15 glass slides representing a spectrum of keratinocytic atypia from AK to SCCIS. Participants were asked to choose 1 or 2 but not 3 grades of KIN that best reflected the changes on each slide. Thirty-two of the 125 solicited enrollees participated in the study. There were 16 volunteers for a total of 48 participants. The inter-observer agreement for all participants was 0.575 (moderate agreement). The overall inter-observer agreement for anatomic pathologist-dermatopathologists (AP-DP), dermatopathologist-dermatologists (DP-D) and anatomic pathologist-dermatologist-dermatopathologists (AP-DP-D) was 0.665, 0.609 and 0.670 (substantial agreement), respectively. There is high concordance among dermatopathologists using a three-tiered diagnostic system for KIN. The observed agreement suggests that dermatopathologists are reliably able to categorize the continuum of keratinocytic atypia in a manner that may have diagnostic relevance.