Immunohistochemical examination of lichen nitidus suggests that it is not a localized papular variant of lichen planus.

BACKGROUND

Lichen nitidus is believed, by some, to be a variant of lichen planus, and by others to be a distinct entity.

OBJECTIVE

We examined five cases of lichen nitidus with immunohistochemical reagents designed to characterize the dermal inflammatory infiltrate in an attempt to resolve the uncertainty.

METHODS

We stained formalin-fixed, paraffin-embedded tissue sections with the following antibodies: L26, A6, KP1, BerH2, OPD4, and HECA-452.

RESULTS

The inflammatory infiltrate was 90% A6+, with few L26+ cells. In contrast to lichen planus, KP1+ macrophages were seen and fewer of the lymphocytes demonstrated HECA-452. Fifty percent to 80% of lymphocytes were OPD4 positive, similar to that usually seen in lichen planus. Rare Ki-1+ cells were seen in one case.

CONCLUSION

We believe that the pattern of a mixed cellular infiltrate characterized by macrophages and a helper T cell response with few HECA-452+ cells is somewhat different from the pattern seen in lichen planus, wherein almost all of the cells are CD4+/HECA-452+ lymphocytes. This suggests a different immunologic pathogenesis.