Pulmonary Marginal Zone B‐Cell Lymphoma of Mucosa‐Associated Lymphoid Tissue (PMZL‐MALT) Diagnosed by Radial Probe Endobronchial Ultrasound–Guided Biopsy: A Case Report

Figures

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  Figure 1. Anteroposterior chest scan in March 2024 shows increased density shadows in the middle field of the right lung and the lower field of the left lung.

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  Figure 2. (a) Plain lung CT scan (August 2025) shows scattered patchy areas of increased density in both lungs; a prominent consolidation with visible air bronchograms is noted in the lingular segment of the left upper lobe. (b) Plain lung CT scan (August 2025) shows scattered patchy areas of increased density in both lungs; a significant consolidation is noted in the upper lobe of the right lung.

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  Figure 3. (a) Enhanced chest CT demonstrates significant enhancement of the lesion in the lingular segment of the left upper lobe, with visible vascular shadows within the lesion (arrow). (b) Enhanced chest CT demonstrates significant enhancement of the lesion in the right upper lobe.

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  Figure 4. (a) Bronchoscopic image of the left upper lobe reveals no endobronchial neoplasms or mucosal abnormalities. (b) Radial probe endobronchial ultrasound (RP‐EBUS)–guided biopsy is performed on the lesion in the left upper lobe, achieving precise localization and successful tissue sampling for histopathological analysis.

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  Figure 5. Radial probe endobronchial ultrasound (RP‐EBUS) image of the left upper lobe reveals abnormal echoes corresponding to the lesion.

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  Figure 6. Pathological and immunohistochemical findings of the left upper lobe lesion. (1) Hematoxylin–eosin (HE) staining (×100). Numerous centrocyte‐like cells are observed. Tumor cells are small, with slightly irregular nuclei and little cytoplasm. (2) HE staining (×200). Mononuclear lymphocytes in the center of the mass exhibit diffuse growth, with cells of moderate size, disrupting the alveolar structure. (3) CD20 immunohistochemical staining (×100). Positive immunoreaction for CD20 is observed in the plasma membrane of tumor cells. (4) CD3 immunohistochemical staining (×100). Partial (focal) positive expression is observed, with scattered and focal positive signals predominantly located in the interstitial and peritumoral regions surrounding the lesion, with clear localization to the cytoplasm and cell membrane of T lymphocytes. No diffuse or strong positive expression is observed in neoplastic cells. (5) CD21 immunohistochemical staining (×100). Disrupted and fragmented follicular dendritic cell networks are observed within the lesion, with scattered, discontinuous positive signals distributed in the lymphoid infiltrate area. No intact lymphoid follicle structure is observed. (6)…