[Endobronchial malignant lymphoma of mucosa-associated lymphoid tissue]

A 56-year-old man presented with pulmonary infiltrates. A chest roentgenogram revealed infiltrates in the left upper lobe and a tomogram showed obstruction of the left upper lobe bronchus. Computed tomography of the chest confirmed the presence these infiltrates, and no lymphadenopathy or mediastinal involvement was detected. At bronchoscopic examination, endobronchial masses were found. These masses almost completely obstructed the distal portion of the left upper lobe bronchus and partly obstructed the right upper lobe bronchus. A left upper sleeve lobectomy was done. Macroscopically, the tumor mass looked like a polypoid growth in the bronchial lumen. Microscopic examination showed that the tumor was composed mainly of small cleaved cells. These cells were observed to have infiltrated the epithelium to form lymphoepithelial lesions. Their B-cell origin was shown by the positive CD19 stain. Monoclonality of tumor cells was shown immunohistochemically and by hybridization techniques. Evidence of monoclonal B-cell proliferation was found in the rearrangement of Ig heavy- and light-chain genes, with Bam HI and Hind III digests. The final diagnosis was distinctive B-cell lymphoma (diffuse, small cell type) of mucosa-associated lymphoid tissue.