Microscopic colitis (MC), encompassing collagenous colitis and lymphocytic colitis, is featured by chronic diarrhea, normal-looking endoscopic findings and unique microscopic appearance. After reviewing biopsied nonspecific colitis, we propose the third type of MC: colitis nucleomigrans (CN). Histopathological criteria of CN included: (i) chained nuclear migration to the middle part of the surface-lining columnar epithelium; (ii) apoptotic nuclear debris scattered below the nuclei; and (iii) mild/moderate chronic inflammation in the lamina propria. Thirty-three patients (M:F = 20:13; median age 63 years, range 17-88) fulfilled our criteria. Seven cases demonstrated MC-like clinical/endoscopic features. Mucosal reddening with or without erosion/aphtha was endoscopically observed in the remaining 26 cases with inflammatory bowel disease (IBD)-like features: occult/gross hematochezia seen in 19, abdominal pain in two and mucin secretion in two. Cleaved caspase-3-immunoreactive apoptotic debris appeared more frequently in IBD-like CN than in MC-like CN, while CD8-positive intraepithelial lymphocytes comparably appeared in both. Proton pump inhibitors (PPIs) were administered in five (71%) cases with MC-like features, and in three diarrhea improved after drug cessation. In IBD-like CN cases, eight (31%) received PPIs. Four patients received chemotherapy against malignancies. Four patients associated immune-related disorders. Microscopic appearance of CN also appeared in a remission state of ulcerative colitis (12/20 lesions).

Bronchiolar adenoma (BA) of the lung is a rare benign neoplasm. Because of a chest abnormal shadow indicated by health checkup, a 77‐year‐old female nonsmoker underwent computed tomography, revealing an 8 mm ground glass nodule in the peripheral field of the right lower lobe. Wedge resection of the nodule was performed, with a frozen diagnosis of primary lung adenocarcinoma. The localized, 8 × 4 × 3 mm‐sized, jelly‐like mass microscopically revealed a lepidic‐growing lesion composed of ciliated columnar cells, mucous cells and basal cells surrounded by mucin pool. Neither nuclear atypia nor mitotic activity was noted. Immunohistochemically, the ciliated, mucous and basal cells were positive for TTF‐1 and p16INK4a. Mucous cells were positive for napsin A and focally expressed MUC5AC. MUC6 was negative. Basal cells were positive for CK5/6, p40, p63 and podoplanin. Human papillomavirus genome was undetectable by in situ hybridization. Ultrastructurally, the bronchiolar epithelial tubules consisted of two layers, the inner nonciliated microvillous cells and the outer basal‐like cells, and some of the inner cells were filled with mucin granules in cytoplasm. Molecular analysis of the tumor failed to show driver mutations. The final diagnosis was distal‐type BA. The postoperative course was uneventful for 6 months.

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