Background: Bronchiolar adenoma (BA) is a recently proposed diagnostic terminology, which is considered as the expansion of the concept of ciliated muconodular papillary tumors (CMPT). BA is considered to be a benign neoplasm, but a few previous cases have been reported with the possibility of malignant transformation. Therefore，the genetic and histological nature of BA is controversial so far. We describe a rare case of multiple BAs with malignant transformation and CCNE1（cyclin E1）mutation to increase the understanding of this disease.Case description: A 56-year-old woman was admitted to our hospital due to two ground-glass nodules (GGNs) in the left lung detected by chest CT without symptom. The pure GGN located in the upper lingual segment about 6 mm in diameter and another mixed GGN located in the dorsal segment about 7 mm. The two GGNs have been found a year ago without treatment, and the mixed GGN become larger to 8 mm with vacuole sign in the next year health checkup. We performed a wedge resection of the two nodules completely by video-assisted thoracoscopy (VATS). Postoperative pathology indicated that the pure GGN was atypical bronchial adenoma, while the mixed GGN was atypical bronchial adenoma with malignant transformation which was missed in frozen section. Gene mutations analysis by next-generation sequencing (NGS) showed CCNE1 gene mutation in both lesions, and her-2 mutation was identified in the mixed GGN. The programmed cell death 1 ligand 1 (PD-L1) expression analysis of tumor cells showed 0% and less than 1% in the pure GGN and the mixed GGN, respectively. Conclusion: BA is generally considered to be a benign tumor. The present study indicated that BA may be carcinogenic in atypical cases with some driver genes mutation and we should be vigilant for its potentiality of malignant transformation in clinical practice.

Background and purpose Central nervous system (CNS) B‐cell lymphoma‐mimicking demyelinating diseases creates a diagnostic dilemma. This study aimed to determine the specific magnetic resonance imaging (MRI) features of CNS B‐cell lymphoma to facilitate the early identification of the disease. Methods We retrospectively reviewed the brain MRI of biopsy‐confirmed CNS B‐cell lymphoma patients. They were initially diagnosed with CNS demyelination, and these images were compared with those of actual patients with demyelinating diseases. Results A total of 20 patients with CNS B‐cell lymphoma and 12 patients with demyelination were included in this study. Cohesive enhancement with satellite enhancing foci surrounded by prominent non‐enhancing areas of oedema is the major contrast‐enhancing pattern of lymphoma patients, accounting for 81% (13) of patients with primary diffuse large B‐cell lymphoma (DLBCL). This imaging pattern revealed a sensitivity of 81% and a specificity of 75% for lymphoma in the differential diagnosis between primary DLBCL and demyelinating disease in our cohort. Among these lesions, most of the nodules were located deeply, which yielded a specificity of 100% and a sensitivity of 69% for primary DLBCL. Enhancement in a single pattern (mainly ring‐like, patchy or punctate; 57%) and no enhancement (30%) were commonly observed in demyelinating lesions, distinct from primary DLBCL (p < 0.05). Conclusions Lesions with cohesive enhancement and satellite foci on T1 contrast‐enhanced imaging could be a specific hallmark of CNS B‐cell lymphoma, suggesting the need to withdraw steroidal therapy and biopsy confirmation.