The Use of Anti-Keratin 903 Antibodies to Visualize Colloid Bodies and Diagnose Lichen Planopilaris.

Cytokeratins are a major component of colloid bodies that are essentially diagnostic of lichen planopilaris (LPP). Here, the authors assess the ability of the cytokeratin 903 antibody (CK-903) to stain colloid bodies and differentiate LPP from other histologically similar appearing primary cicatricial alopecias. A retrospective review of all specimens submitted to the dermatopathology department over a 2-year window identified 18 cases of LPP and 20 cases of histologically similar appearing entities (discoid lupus erythematosus or central centrifugal cicatricial alopecia) through a combination of H&E, elastic van gieson, and periodic acid-schiff stains. All 38 samples were then prospectively stained with CK-903. Colloid bodies were identifiable in 3 of the 18 LPP cases based on H&E alone but were seen in 9 of 18 cases when CK-903 was used. There were no cases where colloid bodies were seen on H&E but not subsequently identified with CK-903. Additionally, there was no CK-903 staining in any of the 20 cases of similar appearing entities except 1 case of discoid lupus erythematosus, which is known to occasionally show colloid bodies. The authors conclude that CK-903 is a useful adjunctive tool that will allow for a quicker, less costly, and more accurate diagnosis of LPP given its ability identify colloid bodies even in the setting of significant inflammation and fibrosis and its advantages over direct immunofluorescence of low cost, short preparation time, and lack of need for a specialized fluorescent microscope.