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Skin - nonmelanocytic tumors

Lymphoma and related disorders

MALT lymphoma


Reviewer: Nikhil Sangle, M.D., University of Utah and ARUP Laboratories (see Reviewers page)
Revised: 27 February 2011, last major update February 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
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● Low grade B cell lymphoma, similar to counterparts elsewhere, that often relapses to skin and subcutaneous tissue

Epidemiology
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● In Scottish Highlands, cutaneous B cell lymphomas are associated with Borrelia burgdorferi / Lyme disease (Am J Surg Pathol 2000;24:1279); they are usually marginal zone subtype, but may be follicular center or diffuse large B cell lymphomas
● Asian cases were not associated with Borrelia DNA, API2-MALT1 fusion nor bcl10 mutation (Am J Surg Pathol 2003;27:1061)

Clinical features
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● Most patients relapse to skin or subcutaneous sites

Case reports
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● Swiss patient with Borrelia associated tumor that regressed after bacterial eradication (Hum Pathol 2000;31:263)
● Germany patient with Borrelia associated tumor outside classical endemic zones, with lesions on nipple (Am J Surg Pathol 2003;27:702)

Micro description
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● May resemble cutaneous lymphoid hyperplasia and cutaneous follicular lymphoma
● Diffuse proliferation of marginal zone cells outside reactive lymphoid follicles; cells are centrocyte-like or monocytoid B cells with plasmacytic differentiation
● No epidermal change or diffuse pattern of dermal or subcutaneous infiltration

Positive stains
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● B cell markers
● Light chains are monotypic
● B cell / T cell ratio is often 3:1 or more (hyperplasia is usually T > B, Am J Surg Pathol 1999;23:88)
● Note: CD21+ follicles may be reactive germinal centers (CD10+, CD20+, bcl6+, bcl2-), MALT lymphoma colonized follicles (CD10-, CD20+, bcl6 variable, bcl2 variable), follicular lymphoma (CD10+, CD20+, bcl6+, bcl2+) or expanded follicular dendritic cell meshworks (bcl6-, bcl2+, Am J Surg Pathol 2001;25:732)

Negative stains
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● CD1a, CD10

End of Skin - nonmelanocytic tumors > Lymphoma and related disorders > MALT lymphoma


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