Miliarial-type reactive B-cell rich proliferation L98.-

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.

1. Barrabés-Torrella C et al. (2025) Miliarial-type reactive B-cell rich proliferation in sun-exposed areas: a diagnostic and therapeutic challenge. J Dtsch Dermatol Ges 23:228-230
2. Jauker P et al. (2021) Miliarial type perifollicular B-cell pseudolymphoma: an easily overlooked rare subtype of pseudolymphoma cutis manifesting as a centrofacial acneiform eruption. J Eur Acad Dermatol Venereol 35:e905-e906
3. Leinweber B et al. (2004) Differential diagnosis of cutaneous infiltrates of B lymphocytes with follicular growth pattern. Am J Dermatopathol 26:4-13.
4. Moreno A et al. (1991) Disseminated, miliarial type lymphocytoma cutis. A report of two cases. Acta Derm Venereol 71:334-336
5. Moulenogeut I (2012) Miliaria-type perifollicular B-cell pseudolymphoma (lymphocytoma cutis): a misleading eruption in two women: miliaria B-cell pseudolymphoma. J Cutan Pathol 39: 1016-1021
6. Villalobos-Ayala RA et al. (2022) Lymphocytoma cutis (cutaneous B-cell pseudolymphoma): study of 102 cases with emphasis on the histological characteristics and immunohistochemistry of the miliarial type. Int J Dermatol 61:316-323.