Primary cutaneous marginal zone B-cell lymphoma.

    Article Contributors: 
    Sean Klepper M.D.
    Stephen Lyle, M.D., ...

    Clinical Features:

    • Recurrent red to brown papules or plaques
    • Most common on the upper extremities and trunk
    • Possible association with Borrelia burgdorferi infection
    • Excellent prognosis

    Histologic Features:

    • Nodular to diffuse lymphocytic infiltrate involving the dermis and upper subcutaneous fat
    • The infiltrate is composed of small mature lymphocytes and monocytoid B-cells.
    • Monocytoid B-cells are medium-sized lymphocytes with abundant clear-staining cytoplasm and indented nuclei.
    • Reactive germinal centers are frequently present, and the neoplastic lymphocytes commonly encroach on the germinal centers.
    • Focal to extensive plasma cell differentiation is common.
    • The epidermis is characteristically spared.
    • The immunophenotype is nonspecific, with positivity for pan-B-cell markers.
    • If plasmacytic differentiation is present, immunohistochemical staining for immunoglobulin light chains may demonstrate kappa or lambda light chain restriction, proving the clonal nature of the process.

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