This study was designed to evaluate whether CD10, podoplanin (D2-40), and Ki-67 could reliably differentiate trichoepithelioma (TE) from basal cell carcinoma (BCC) and whether these proteins could be used as markers of basaloid epidermal proliferation (BEP) of nevus sebaceous (NS). The clinico-pathological characteristics of 11 TE, 19 BCC, and 23 NS cases with BEP were analyzed. CD10, podoplanin, and Ki-67 expression was evaluated by immunohistochemistry. Eight out of 11 (72.7%) TE cases expressed CD10. In 7 cases, CD10 was expressed only in the stroma, while stromal expression of CD10 was detected in 1 (5.3%) case of BCC. Twelve (63.2%) BCC cases only expressed CD10 in tumor cells. Seven out of 11 (63.6%) TE cases presented D2-40 staining. The staining was diffused in 4 cases (36.4%) and focally positive in 3 cases (27.3%). In BCC, only 6 of 19 (31.6%) cases stained for D2-40 and most cases were focally positive (26.3%). Mean Ki-67 labeling index of TE cases was 15.5, while that of BCC cases was 36.6. Cases presenting NS with BEP were less positive for CD10 (34.8%) and D2-40 (26.1%) compared to TE and BCC cases. Six cases presenting NS with BEP (26.1%) demonstrated CD10 positivity only in the stroma, and two cases (8.7%) presented CD10 positivity only in tumor cells. Mean Ki-67 labeling index of NS with BEP was 10.9. In conclusion, immunohistochemistry analysis demonstrated that CD10 and Ki-67 are reliable markers to differentiate TE from BCC. Additionally, NS presented a less aggressive biologic behavior in the BEP areas.
