Immunophenotyping as a diagnostic tool to differentiate lichen planus from chronic graft-versus-host disease: diagnostic observations on two patients.

BACKGROUND

Lichen planus (LP) and the lichenoid variant of chronic graft-versus-host disease (cGVHD) can present with similar clinical and histological findings. The distinction, although difficult, is important both prognostically and therapeutically. The mechanism and effector cell phenotypes have also shown to differ between the 2 entities. While the lichenoid infiltrate of LP is predominantly T lymphocytes helper/inducer cell phenotype, the suppressor/cytotoxic subset appears to play a major role in cGVHD. The aim of this study is to determine whether the immunophenotypic character of the lichenoid infiltrate can aid in distinguishing the 2 entities.

METHODS

Biopsies were obtained from 2 patients with lichenoid papules and a history of transplantation. Light microscopy revealed lichenoid inflammation in both cases characterized by a band-like lymphohistiocytic infiltrate at the dermal-epidermal junction. Immunochemistry was performed on fresh tissue using a panel of monoclonal antibodies including anti-CD1a, CD3, CD4, CD8, CD16, CD20, CD28, and CD68. Results were quantitated using computer-assisted image analysis.

RESULTS

We found that in both cases the majority of cells stained with pan T cell marker CD3+. One case demonstrated predominantly CD4+ T cells and increased numbers of CD1a positive Langerhans cells, while the lymphokine natural killer cell activity (LAK) markers anti-CD16 and anti-CD28 were largely nonreactive. Conversely, the second case contained predominately CD8+ lymphocytes and very few CD1a positive Langerhans cells with abundant LAK cell anti-CD16 and anti-CD28 reactivity.

CONCLUSIONS

Based on these findings, the former was classified as lichen planus and the latter as lichenoid cGVHD. The diagnoses are substantiated with clinical history and follow-up information. We conclude that immunophenotypic characteristics of the infiltrate can be a useful tool in differentiating lichenoid cGVHD from lichen planus.