The role of MT2 and anti-bcl-2 protein antibodies in the differentiation of benign from malignant cutaneous infiltrates of B-lymphocytes with germinal center formation.

MT2/CD45RA and anti-bcl-2 protein (Bcl-2) monoclonal antibodies are useful markers in distinguishing follicular lymphomas from reactive follicular hyperplasia of the lymph nodes. We examined biopsy specimens from 11 patients with primary cutaneous B-cell follicle center lymphomas, 10 patients with cutaneous pseudolymphomas with germinal centers, and 6 patients with inflammatory infiltrates with germinal centers in non-lymphoid cutaneous tumors (3 basal cell carcinomas, 2 malignant melanomas, and 1 solar keratosis), in order to evaluate the utility of MT2 and anti-Bcl-2 antibodies in differentiating benign from malignant germinal center cell proliferations in the skin. Immunohistochemical evaluation of MT2 and Bcl-2 was focused exclusively on the reactivity of germinal center cells. Specific membranous MT2 positivity was found in 2/11 cutaneous follicle center lymphomas; a diffuse, non-specific staining pattern was identified in 3/11 follicle center lymphomas and in 1/6 inflammatory infiltrates in non-lymphoid tumors. A negative MT2 reaction was observed in 6/11 follicle center cell lymphomas, in all cases of pseudolymphomas and in 5/6 inflammatory infiltrates in non-lymphoid tumors. Bcl-2 positivity was detected only in 1/11 follicle center lymphomas. Germinal center cells in all other cases were Bcl-2 negative. Our results suggest that MT2 and anti-Bcl-2 antibodies are only of limited value in differentiating primary cutaneous follicle center lymphomas from cutaneous pseudolymphomas with germinal centers.