Lung tumor - MALT lymphoma

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Lung tumor

Lymphoma and lymphoid infiltrates

MALT lymphoma

Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 22 January 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Lymphoma of Mucosal Associated Lymphoid Tissue - a type of marginal zone lymphoma
● See also lymphoma of bronchial associated lymphoid tissue (BALT)
● Called pseudolymphoma in older literature
● In adults, lung MALT is usually low-grade, median age 68 years (range 34-88), often associated with autoimmune disorders, monoclonal gammopathies, hepatitis C, Helicobacter pylori gastritis
● 44% involve mediastinal nodes
● Usually indolent with excellent prognosis (Am J Surg Pathol 2001;25:997)
● May recur locally, rarely transforms, few die of disease
● 20% have monoclonal gammopathy, 30% have pleural effusions
● Flow cytometry of tumor cells is useful in phenotyping; may even be helpful on peripheral blood

Etiology
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● In pediatric HIV patients with lymphoid interstitial pneumonitis, chemokines and cytokines may recruit inflammatory cells, either representing an early stage of MALT or providing a microenvironment for the evolution of a monoclonal B-cell population (Mod Pathol 2001;14:929)

Case reports
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● 41 year old woman with multiple lung nodules, negative flow cytometry but clonal IgH gene rearrangement (Arch Pathol Lab Med 2003;127:115)

Treatment
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● Local resection for limited disease, chemoradiotherapy for advanced disease

Gross description
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● Solitary discrete mass, occasionally multiple nodules

Gross images
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Discrete tan mass (contributed by anonymous)

Micro description
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● Nodular pattern of monotonous, mature lymphocytes with germinal centers that infiltrate overlying epithelium (lymphoepithelial lesions) and around vessels, pleura and alveolar septa
● Cells may be monocytoid or resemble centrocytes
● Also reactive plasma cells, variable fibrosis and epithelioid granulomas
● Also colonization of germinal centers by tumor cells
● Rarely granulomatous vasculitis

Micro images
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Monotonous population of small-intermediate cells (contributed by anonymous)

Lymphoepithelial lesion (contributed by anonymous)

Figure 1-CT with multiple pulmonary nodules; 2A-lymphocytic proliferations with some germinal centers; 2B-lymphoepithelial lesions associated with bronchial mucosa

Positive stains
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● CD20, CD43

Negative stains
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● CD5, CD10, CD23

Differential diagnosis
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● Benign lymphoid aggregates / reactive disorder: architecture is preserved, associated with immunosuppression and collagen vascular disease; not monoclonal by flow cytometry or PCR (Am J Surg Pathol 2002;26:76)

End of Lung tumor > Lymphoma and lymphoid infiltrates > MALT lymphoma

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