IMMUNOPHENOTYPING AS A DIAGNOSTIC-TOOL TO DIFFERENTIATE LICHEN-PLANUSFROM CHRONIC GRAFT-VERSUS-HOST DISEASE - DIAGNOSTIC OBSERVATIONS ON 2PATIENTS

Background: Lichen planus (LP) and the lichenoid variant of chronic gr aft-versus-host disease (cGVHD) can present with similar clinical and histological findings, The distinction, although difficult, is importa nt both prognostically and therapeutically. The mechanism and effector cell phenotypes have also shown to differ between the 2 entities, Whi le the lichenoid infiltrate of LP is predominantly T lymphocytes of he lper/inducer cell phenotype, the T 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 transplantati on. Light microscopy revealed lichenoid inflammation in both cases cha racterized by a band-like lymphohistiocytic infiltrate at the dermal-e pidermal 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-as sisted image analysis, Results: We found that in both cases the majori ty of cells stained with pan T cell marker CD3+, One case demonstrated predominantly CD4+ T cells and increased numbers of CD1a positive Lan gerhans 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 a nti-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 infor mation, We conclude that immunophenotypic characteristics of the infil trate can be a useful tool in differentiating lichenoid cGVHD from lic hen planus.