Miliarial-type reactive B-cell rich proliferationL98.-

Miliarial-type reactive B-cell rich proliferation (rBLP), a small papular miliaria-like lymphocytoma variant of the skin, is a rare clinicopathologic subtype of cutaneous lymphocytoma (older name: lymphadenosis cutis beniga) characterized clinically by numerous translucent, asymptomatic micropapules located on the exposed areas of the head and neck.

Not secured; w>m (?)

Unexplained; an exacerbation (triggering?) after sun exposure is described.

Middle age (40-60 years)

Sunlight-exposed areas on the head and neck.

Numerous 0.1-0.2 cm large, symmetrically distributed, skin-colored or reddish, sometimes translucent, asymptomatic or slightly itchy papules on the head and neck. The papules are solitary, but can also aggregate.

Characteristics of a cutaneous "miniature lymphocytoma" with a superficial, non-epidermotropic, nodular infiltrate expressing small, well-circumscribed germinal centers with "tingible-body macrophages" surrounded by a distinct mantle zone.

Cells are ^CD20+, co-expression of BCL6 (follicular cell marker); Ki-67 positive in the follicular centers.

Polymerase chain reaction analysis of IgH gene rearrangement shows no clonal B-cell population.

Acne vulgaris (age unusual)

Rosacea: absence of flat, reactive erythema

Lupus erythematosus: Histology (lichenoid infiltrate) and immunohistology (IgG deposits on the basement membrane) are diagnostic

Lupus miliaris disseminatus faciei: histology: lupoid infiltrates

Miliaria-like primary cutaneous follicle center lymphoma (PCFCL): clinically and histopathologically difficult to differentiate: histologically pathological germinal center structure; monoclonal immunoglobulin chains, resistance to therapy. The histopathological finding of a "top-heavy" lymphocytic infiltrate, which is predominantly located in the upper layers of the skin, supports the diagnosis of benignity.

Improvement under treatment with hydroxychloroquine.

Miliaria-like reactive B-cell proliferation represents multifocal hyperplasia of B lymphocytes with follicular differentiation and formation of follicular germinal centers. The development of the disease is characteristic, with some of the lesions healing and others persisting in a nodular form. The disease is chronic and heals completely after one to several years.

Note: The distinction between Miliaria-like reactive B-cell proliferation and Miliaria-like primary cutaneous follicle center lymphoma (PCFCL) can be difficult due to the clinical and histologic similarity of the entities.

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