Reduced number of CD1a+cells in cutaneous B-cell lymphoma

Cutaneous B-cell lymphoma is difficult to distinguish from pseudolymphoma. The histologic pattern and monoclonal restriction (immunohistochemical anal ysis and molecular biology) are the criteria used for differentiating, thes e entities. CD1a+ dendritic cells have been observed in the infiltrates of T-cell lymphoma, but the presence of these CD1a+ cells has nor been compare d in B-cell lymphoma and pseudolymphoma. We studied the presence of CD1a+ c ells on frozen sections of 23 B-cell lymphomas, 13 pseudolymphomas, and 17 T-cell lymphomas by immunohistochemical analysis. We found abundant CD1a+ d endritic cells in only 1 (4%) of 23 B-cell lymphomas, whereas in 8 (62%) of 13 pseudo-lymphomas and 17(100%) of 17 T-cell lymphomas, strong CD1a stain ing was present. Our study demonstrates a distinct pattern of CD1a staining in the infiltrates of B-cell lymphoma and pseudolymphoma that may be of va lue in the differential diagnosis of these skin disorders.