Immunoreactivity for bcl-2 protein in cutaneous lymphomas and lymphoid hyperplasias

The B-cell leukemia/lymphoma gene (bcl-2) produces a unique protein product (BCLP) that is believed to protect lymphoid cells from apoptosis. The bcl-2 gene is frequently rearranged in nodal follicular lymphomas as well as in diffuse lymphoproliferations, but has generally been regarded as most useful in the recognition of the former of these lesions. However, little is known regarding BCLP expression in cutaneous lymphoid infiltrates. Using an immunohistochemical technique and a monoclonal antibody (clone no. 124) the authors examined 67 examples of cutaneous lymphoid infiltrates--31 cases of malignant lymphoma of the skin (MLS) and 36 examples of cutaneous lymphoid hyperplasias (CLH)--to determine if patterns of BCLP reactivity could distinguish CLH from MLS or primary from secondary involvement of the skin by malignant lymphoma. Fifty-eight per cent of MLS cases were BCL-positive, as were 33% of CLH. Three of four cases of follicular cutaneous lymphoma showed BCLP-positivity in neoplastic follicles, whereas similar structures in cases of CLH with a follicular pattern were BCLP-negative. Sixty per cent of primary MLSs and 57% of secondary lymphomas were reactive for BCLP. These data suggest that immunostains for BCLP are of little help in the separation of benign from malignant cutaneous lymphoid infiltrates, and that they are likewise incapable of separating primary from secondary MLS. BCLP immunostains may have a limited adjuvant diagnostic role in distinguishing reactive from neoplastic follicular lymphoid lesions of the skin.