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.

Bcl-2, CD34 and CD10 expression in basaloid follicular hamartoma, vellus hair hamartoma and neurofollicular hamartoma demonstrate full follicular differentiation.

Generalized basaloid follicular hamartoma syndrome (GBFHS) is a rare, recently-described, autosomal-dominantly inherited disorder that presents with disseminated milia, palmoplantar pitting, hypotrichosis and basaloid follicular hamartomas (BFH). BFH is a benign adnexal tumor that resembles basal cell carcinoma (BCC). In this study, we report two cases of GBFHS and stain BFH, a vellus hair hamartoma (VHH) and a neurofollicular hamartoma (NH) with CD34, bcl-2 and CD10 to characterize and compare the staining patterns of these follicular tumors. Standard immunohistochemistry labeling with CD34, bcl-2 and CD10 was performed on paraffin-embedded, formalin-fixed tissue sections of five BFH (four for CD10), one VHH and one NH. CD34 stromal staining was observed in all specimens. Bcl-2 stained the outermost cell layers of the basaloid nests in all specimens. CD10 stained the peritumoral stroma of all specimens. The BFH, NFH and the VHH showed CD10 staining of matrical cells. CD34 and CD10 stain peritumoral stroma of BFH, VHH and NH. Bcl-2 stains the outermost cell layer of these tumors. CD10 was also observed to stain matrical cells. These results show the similarities in differentiation between these benign follicular neoplasms and trichoepithelioma.