Marginal zone B-cell lymphoma of the pulmonary mucosa-associated lymphoid tissue: A case report.

Marginal zone B-cell lymphoma of the pulmonary mucosa-associated lymphoid tissue (pulmonary MALT-MZL) is a common type of primary pulmonary lymphoma, but is rare as a pulmonary malignant tumor. In the present study, a 49-year-old male patient was admitted to The First Affiliated Hospital of Xi'an JiaTong University (Xi'an, China) with a pulmonary lesion in the right upper lung. The patient was diagnosed with pulmonary MALT-MZL subsequent to undergoing chest computed tomography (CT), a routine blood test, pathological and histological examinations, a transbronchial lung biopsy and bronchoscopy. A chest CT scan revealed right middle lobe consolidation and inflammatory signs, accompanied by mediastinal lymphadenopathy in the anterior basal segment of the upper lobe and CT angiogram signs. Bronchial stenosis and swollen mucosa were observed by bronchoscopy. The tissue section of the transbronchial lung biopsy specimens revealed diffusely infiltrated monocytoid B-cell lymphocytes and a lymphoepithelial lesion. The tissue was found to be positive for cluster of differentiation (CD)20, B-cell lymphoma 2 and CD79a expression, but negative for CD3, CD5, cyclin D1 and κ-light chain expression. CD21 and CD23, located in the residual follicular dendritic cells, were detected by immunohistochemical staining. The clinical manifestations of pulmonary MALT-MZL are non-specific and misdiagnosis frequently occurs in clinical practice. Therefore, an appropriate invasive biopsy procedure is necessary for early and accurate diagnosis of pulmonary MALT-MZL. Clinical presentation that includes periodic fever and distended bronchi in pulmonary consolidation may indicate a diagnosis of MALT-MZL. Pulmonary MALT-MZL belongs to the category of indolent lymphoma and accurate clinical diagnosis is challenging. The results in the present study may provide additional evidence for the accurate diagnosis of this rare entity.