Impact of molecular analysis in the diagnosis of cutaneous lymphoid infiltrates

The diagnosis and classification of cutaneous lymphomas is a challenge for the dermatopathologist. This is particularly true for determining the disti nction between a malignant lymphoma and a benign reactive infiltrate (pseud olymphoma). Recent advances in molecular genetics, as the determination of clonality of lymphoid infiltrates, have emerged as an important tool to ove rcome these diagnostic dilemmas. In our experience, more than 90% of cutane ous T-cell lymphomas have a rearrangement of the T-cell receptor gamma chai n gene, whereas clonal rearrangements in cutaneous T-cell pseudolymphomas c ould not be found. However, the demonstration of clonality does not necessa rily indicate malignancy. There have been several reports that have identif ied clonal lymphoid proliferations in pityriasis lichenoides et varioliform is acuta, pseudolymphomas, and lichen planus. For this reason one must care fully evaluate the information that is provided by these techniques, The re sults should always correlate with clinical, histologic, and immunophenotyp ic data to achieve the correct diagnosis, Copyright (C) 2000 by W.B. Saunde rs Company.