Primary cutaneous B-cell lymphoma

Primary cutaneous B-cell lymphoma (PCBCL) is a group of rare non-Hodgkin lymphomas that originate in B-lymphocytes and primarily involve the skin without evidence of extracutaneous disease at the time of diagnosis. This condition encompasses several subtypes, including primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle center lymphoma (PCFCL), and primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT). The disease predominantly affects the skin, presenting as solitary or grouped reddish to violaceous papules, plaques, or nodules, most commonly on the head, trunk, or legs depending on the subtype. PCMZL and PCFCL are considered indolent subtypes with an excellent prognosis, while PCDLBCL-LT follows a more aggressive clinical course with a higher risk of extracutaneous dissemination. The exact cause of primary cutaneous B-cell lymphoma is not fully understood, but it is not considered a hereditary condition. In some cases, chronic antigenic stimulation, including infections such as Borrelia burgdorferi in certain geographic regions, has been implicated in the pathogenesis of the marginal zone subtype. Diagnosis requires skin biopsy with histopathological examination, immunohistochemistry, and staging investigations to exclude systemic lymphoma involvement. Treatment depends on the subtype and extent of disease. Indolent forms may be managed with local therapies including surgical excision, radiotherapy, or intralesional corticosteroids. For more aggressive subtypes or widespread disease, systemic therapies such as rituximab (an anti-CD20 monoclonal antibody), alone or in combination with chemotherapy regimens like R-CHOP, may be employed. Regular follow-up is essential as cutaneous relapses are common, particularly in indolent subtypes, although these recurrences generally do not affect overall survival.

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