Distinguishing immunohistochemical features of alopecia areata from androgenic alopecia.

Characterization of CD3 and CD8 in IHC samples is helpful, especially when the density of CD3 and CD8 T cells are significant in more than 50% of the infiltrated cells and are located intrafolliculary. Moreover, the most specific and sensitive test for differentiating of AA from AGA is CD3.