Methotrexate-associated B-cell lymphoproliferative disorders presenting in the skin: A clinicopathologic and immunophenotypical study of 10 cases.

Methotrexate (MTX)-associated B-cell lymphoproliferative disorders (B-LPD) may first present in the skin, but their clinicopathologic features are still ill defined. Differentiation from primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL-LT) is important, as MTX-associated B-LPD may show spontaneous regression after withdrawal of MTX therapy. In the present study, the clinicopathologic and phenotypical features of 10 patients with MTX-associated B-LPD first presenting in the skin, including 5 EBV(+) and 5 EBV(-) cases, were investigated. Six patients had skin-limited disease. Clinically, abrogation of MTX therapy resulted in a complete response in 4 cases and a partial response in another 2. The 5-year disease-specific survival was 90%. MTX-associated B-LPD differed from primary cutaneous follicle center lymphoma by the presence of ulcerating and/or generalized skin lesions, an infiltrate composed of centroblasts/immunoblasts rather than large centrocytes, reduced staining for CD79a, and expression of BCL2, IRF4, and FOXP1 in most cases. EBV(+) MTX-associated B-LPD differed from PCLBCL-LT by the presence ulcerative skin lesions, marked tumor cell polymorphism, reduced staining for CD79a, and expression of CD30 and EBV. EBV(-) cases showed morphologic and immunophenotypical similarities to PCLBCL-LT but differed by presentation with generalized skin lesions in 4 of 5 cases. The results of this study, showing a relatively good clinical outcome and spontaneous disease regression after only withdrawal of MTX in a considerable proportion of patients, underscores the importance of a careful wait-and-see policy before considering more aggressive therapies in patients with MTX-associated B-LPD of the skin.