D2-40 Expression in Primary Scarring and Nonscarring Alopecia

Tricholemmoma and clear cell squamous cell carcinoma (associated with Bowen's disease): immunohistochemical profile in comparison to normal hair follicles

There have been only a few reported comparative immunohistochemical studies of normal hair follicles and tricholemmomas. Clear cell squamous cell carcinomas (SCCs), which are derived from Bowen's disease, histopathologically mimic or are difficult to distinguish from tricholemmal carcinoma. The purpose of and methods used in the present study are as follows: (1) evaluation of whether the immunohistochemical profile (cytokeratin (CK)1, CK10, CK17, CD34, and D2-40) in normal hair follicles is retained in tricholemmomas (11 lesions); and (2) a study of the immunohistochemical profile of in situ or superficially invasive clear cell SCCs (associated with Bowen's disease) (10 lesions) to investigate the presence or absence of tricholemmal differentiation markers in these lesions. The present study demonstrated that (1) the immunohistochemical profile of the normal outer root sheath cells was generally retained in tricholemmomas; (2) in contrast to the D2-40 expression in tricholemmomas (only a peripheral pattern, which is similar to that in the normal outer root sheath), the CD34 expression in tricholemmomas represented in a diffuse pattern, a peripheral pattern, and a combined diffuse and peripheral pattern; (3) tricholemmomas are benign neoplasms with outer root sheath (below the isthmus) differentiation, which characteristically show upregulation of CD34 expression with some functionally similar conditions to the terminal hair follicles in the anagen phase; and (4) there is no clear immunohistochemical evidence of tricholemmal differentiation in clear cell SCC (associated with Bowen's disease).