Skin, Primary cutaneous marginal zone lymphoma, CD20 stain [LMP72002]

87 year old female with a history of non-melanoma skin cancer who presented with a slowly growing papule on the left chest, that clinically was suspected to be a basal cell carcinoma.

Primary cutaneous B cell lymphomas (PCBCL) constitute the minority (20-30%) of cutaneous lymphomas (with T cell subtype composing the majority of cases). They are classified into 3 main types: follicle center, marginal zone, and diffuse large B cell. Primary cutaneous marginal zone lymphoma (PCMZL) shows indolent clinical behaviour and excellent prognosis, with a survival rate in 5 years >95%. There is an extremely low risk for systemic dissemination, but cutaneous recurrences are common.

Histologically, there is nodular or diffuse expansion of the marginal zone by atypical uniform lymphocytes. These marginal zone B-cells obscure and infiltrate germinal centers, and there is usually associated plasma cells at the periphery of the infiltrate. PCMZL cells are CD20+ and BCL-2+, and these cells do not express CD10, BCL-1 or cyclin D1. Immunohistochemical analysis may otherwise be normal, but there can be light chain restriction, positive monoclonality by molecular testing and cells can co-express CD43.

This slide shows CD20 stain. See related content for H&E, CD43, and Kappa stains.