IRTA1 expression in MALT lymphomas. (A) Gastric MALT lymphoma. Tumor cells forming lympho-epithelial lesions are IRTA1⁺. ^* indicates a gland lumen. Tumor cells located far from the glandular epithelium are IRTA1^-. (B) Lympho-epithelial lesion in a MZ lymphoma of the lung. The arrow points to a IRTA1⁺ lymphoma cells invading the ciliated bronchial epithelium. The APAAP technique with mAb M-IRTA1 was used with a hematoxylin counterstain. Original magnifications × 200 (A); × 1000 (B).