PRIMARY CUTANEOUS MARGINAL ZONE B-CELL LYMPHOMA - A RECENTLY DESCRIBED ENTITY OF LOW-GRADE MALIGNANT CUTANEOUS B-CELL LYMPHOMA

Recently a new classification of primary cutaneous B-cell lymphomas (P CBCLs) has been proposed by the European Organization for Research and Treatment of Cancer (EORTC)-Cutaneous Lymphoma Project Group. The mar ginal zone B-cell lymphomas (MZLs) were not included as a distinct ent ity because of insufficient experience and controversial opinions. We have studied 32 patients (M:F ratio 1.5:1; age range 25-93 years; mean age 49.6 years; median age 50 years) to determine the diagnostic crit eria of primary cutaneous MZL and the relationship with other low-grad e malignant PCBCLs, For com parison, three patients with immunocytoma were included in the study. Clinically, patients presented with solita ry or clustered reddish or red-brown papules, nodules, and plaques, so metimes surrounded by an erythematous halo, Histopathologic sections s howed nodular or diffuse infiltrates involving the dermis and subcutan eous fat. Cytomorphologically small to medium-sized cells with indente d nuclei and abundant pale cytoplasm (marginal zone cells, centrocytel ike cells) predominated. In addition, scattered blasts, lymphoplasmacy toid cells, and plasma cells were observed below the epidermis and at the periphery of the infiltrates. Reactive germinal centers were prese nt in 75% Of the cases. The three cases of immunocytoma showed a more monomorphous pattern with predominance of lymphoplasmacytoid cells. Th e marginal zone cells showed a CD20(+), CD79a(+), CD5(-) and Bcl-2(+) immunophenotype. They expressed immunoglobulin G in the majority of th e cases, Staining with the monocytoid B cell-related antibody KiM1p ga ve positive results in all specimens with a typical intracytoplasmic g ranular pattern. A monoclonal distribution of immunoglobulin light cha ins was observed in marginal zone cells in 75% of the cases. Germinal centers, when present, were either polyclonal or negative for both kap pa and lambda light chains. Monoclonal rearrangement of the J(H) gene was detected via polymerase chain reaction (PCR) in 18 of 26 investiga ted specimens. Analysis in 12 patients of the bcl-2/immunoglobulin hea vy chain gene rearrangement using PCR yielded negative results. Lesion s were treated by surgical excision followed in some patients by local radiotherapy. Systemic antibiotic therapy was administered to three p atients, with good response in two. The prognosis is excellent. After a mean follow-up of 47.9 months (range 6-252; median 24) all patients are alive without signs of systemic lymphoma. Primary cutaneous MZL re presents a distinct clinicopathologic subtype of low-grade malignant P CBCL.