Definition
This is a type of extranodal marginal zone lymphoma. The neoplastic lymphoid cells characteristically infiltrate the bronchiolar epithelium to form lymphoepithelial lesions.
Marginal zone lymphoma accounts for less than 0.5% of all lung neoplasms and of all lymphomas, but constitutes 70-90% of all lung lymphomas. It is not uncommon for patients to have extranodal MALT lymphoma at other sites.
Most patients are older adults. Marginal zone lymphoma in young adults is usually associated with immunosuppression. Autoimmune disease and monoclonal gammopathies are common8,11.
Lesions are usually peripheral. There may be a solitary nodule9, multiple nodules9 or diffuse bilateral disease: unilateral disease is more common than bilateral8. Associated findings are air bronchograms, airway dilatation, a positive angiogram sign and a halo of ground-glass shadowing at lesion margins7. Peribronchovascular thickening may also observed, as may hilar or mediastinal lymph node enlargement and pleural effusions or thickening7.
Resembles lymphoma of lymph node. Rarely, there may be cystic degeneration.
The histopathology resembles that of extranodal marginal zone lymphoma at other sites. In most cases, reactive follicles are smaller than those seen in gastric MALT lymphoma. Although the formation of lymphoepithelial lesions is characteristic2, they may also be seen in non-neoplastic pulmonary lymphoid infiltrates3. The lymphoid infiltrate often tracks along bronchovascular bundles3,10 and interlobular septa10, leaving airways intact, and may involve the pleura3. Invasion of bronchial cartilage favours malignancy6. Centrally, the lung parenchyma is destroyed and there may be sclerosis10: in some cases, the hyalinosis may be a dominant feature13. There may be epithelioid histiocytes, giant cells or granulomata13. Giant lamellar bodies may occur1. Amyloid deposition may be seen. A case with massive crystal storing histiocytosis has been reported14.
Tumours with a predominance of large cells should be designated as diffuse large B-cell lymphoma: often there is evidence of a pre-existing low grade MALT lymphoma3,8.
As for extranodal marginal zone lymphoma at other sites. Light chain restriction is diagnostically very useful, but may be masked by polyclonal reactive follicles and plasma cells2. The neoplastic cells are usually positive for bcl-2 and bcl-1012 and show an aberrant phenotype CD20+/CD 43+3. CD21, CD23 and CD35 highlight the meshwork of expanded follicles overrun by neoplastic cells10. Anticytokeratins high-light lymphoepithelial lesions10.
Clinically: sarcoid, organising pneumonia, infections, bronchoalveolar carcinoma, amyloidosis.
Histologically:
Nodular lymphoid hyperplasia (NLH): B cells form abundant follicles4 with preserved mantles and the interfollicular area consists of T-cells and numerous polyclonal plasma cells4, with variable fibrosis4. The bronchial cartilage and pleura are not invaded. The follicles are negative for bcl-2. Lymphadenopathy and pleural effusion suggest lymphoma, although lymphadenopathy may be seen in NLH4. There is a lack of rearrangement of the immunoglobulin heavy chains in NLH4.
Lymphoid interstitial pneumonia: does not destroy the alveolar architecture.
Follicular bronchiectasis.
If there is prominent hyalinosis: pulmonary hyalinising granuloma or inflammatory pseudotumour.
Nodular amyloidosis: these are non-neoplastic inflammatory foci associated with amyloid deposition5. Marginal zone lymphoma of the lung may produce amyloid. Features that favour MALT lymphoma associated with amyloid are lymphatic tracking of the lymphocytic infiltrate, pleural infiltration, sheet-like masses of plasma cell and the presence of reactive follicles, a dominance of B-cells, an aberrant phenotype (CD20+/CD43+) and light chain restrictions5.
See other low grade non-Hodgkin's lymphomas: immunophenotypes
If resectable, surgery. Otherwise as for lymphoma elsewhere.
MALToma of lung tends to remain localised2, conferring a good prognosis and potential for cure. Spread may occur to lymph nodes, stomach or salivary glands9. Five year survival is 84-94%, 72% at ten years8. A few cases progress to diffuse large B-cell lymphoma.
Tumours of the Lung, Pleura, Thymus and Heart. WHO Classification of Tumours. IARC Press 2004.
This page last revised 31.1.2006.
©SMUHT/PW Bishop