Primary cutaneous marginal zone B-cell lymphoma

Primary cutaneous marginal zone B-cell lymphoma (PCMZL), also known as primary cutaneous MALT lymphoma or extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) arising in the skin, is a rare, indolent (slow-growing) type of non-Hodgkin lymphoma that originates in the B-lymphocytes of the skin. It belongs to the group of primary cutaneous B-cell lymphomas and is classified among the low-grade cutaneous lymphomas with an excellent prognosis. The disease primarily affects the skin, presenting as solitary or multiple red to violaceous papules, plaques, or nodules, most commonly located on the trunk, arms, or head. Lesions are typically painless and may persist or slowly enlarge over months to years. Systemic dissemination (spread to internal organs) is rare, and the disease generally remains confined to the skin. PCMZL predominantly affects adults, with a median age of onset typically in the fifth to sixth decade of life, though it can occur at various ages. In some cases, an association with Borrelia burgdorferi infection has been reported, particularly in European populations, suggesting a possible role of chronic antigenic stimulation in disease pathogenesis. Diagnosis is established through skin biopsy with histopathological examination and immunohistochemistry, which typically reveals infiltrates of small B-cells expressing CD20 and BCL-2 but lacking CD10, CD5, and BCL-6. The prognosis for PCMZL is excellent, with a 5-year disease-specific survival rate exceeding 95%. Treatment options depend on the extent of disease. For solitary or localized lesions, local therapies such as surgical excision, local radiotherapy, or intralesional corticosteroid injections are commonly employed. In cases associated with Borrelia infection, antibiotic therapy may lead to regression. For patients with multifocal skin lesions, options include rituximab (systemic or intralesional), chlorambucil, or watchful waiting given the indolent nature of the disease. Relapses in the skin are common but do not adversely affect overall survival.

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