A review of 55 cases of cutaneous lymphoid hyperplasia: reassessment of the histopathologic findings leading to reclassification of 4 lesions as cutaneous marginal zone lymphoma and 19 as pseudolymphomatous folliculitis.

To clarify the confusion surrounding the diagnosis of cutaneous lymphoid hyperplasia (CLH) that was formerly described as lymphadenosis benigna cutis, lymphocytoma cutis, or lymphocytic infiltration of Jessner and to assess whether newly recognized diagnoses, such as cutaneous marginal zone lymphoma and pseudolymphomatous folliculitis (PLF), may have been overlooked, we reexamined 55 Japanese cases of nonepidermotropic lymphoproliferative disorder that had previously been diagnosed as "cutaneous pseudolymphoma." In all these cases, the immunohistochemical expressions of CD1a, CD3, CD4, CD8, CD20, CD21, CD30, CD43, CD56, CD68, CD79a, kappa and lambda chains, S-100 protein, and latent membrane protein were assessed. In addition, in 13 cases the gene rearrangement of the immunoglobulin heavy chain was investigated using a polymerase chain reaction method. As a result of these investigations, we have identified 4 cases of cutaneous marginal zone lymphoma, 19 cases of PLF, 1 case of diffuse large B-cell lymphoma, and 2 cases of solitary nonepidermotropic pseudo-T-cell lymphoma, with the remaining 29 cases being CLH. Cutaneous marginal zone lymphoma, which represented 7.3% of the total, was distinguished from CLH by the presence of patchy or diffuse proliferation of centrocyte-like cells, plasma cells at the periphery of the lymphocytic infiltration, monotypic restriction of the light chains, and gene rearrangement of the immunoglobulin heavy chain. Pseudolymphomatous folliculitis was identified by the presence of activated pilosebaceous units with abundant CD1a-and S-100 protein-positive T-cell-activated dendritic cells. Of the cases that were reassessed, 34.5% were PLF.