Peripheral mucous gland adenoma of the lung with parenchymal involvement and smooth muscle in the stroma: A rare case report and literature review

RATIONALE: Mucous gland adenoma is an extremely rare benign tumor predominately presented in central bronchus. Thus far, only six cases located in the periphery have been reported in English literature. PATIENT CONCERNS: Herein, we report a case located in periphery of the lung with parenchymal involvement in a 59-year-old female. Histologically, the tumor appeared as peripheral lobulated and solid mass with the pushing border. The tumor was composed of abundant irregular glands, mucus-filled acini and tubules lined by bland cuboidal to columnar mucus-secreting epithelial cells lacking cellular atypia and mitotic activities. Moreover, the tumor contained fibromyxoid stroma with smooth muscular bundles and prominent lymph follicles, which has not been reported in previous cases. DIAGNOSIS: Based on the morphological profile and immunohistochemical staining, the tumor was diagnosed as a mucous gland adenoma. INTERVENTION: The patient then underwent wedge resection in our hospital. OUTCOMES: The patient was alive with no tumor recurrence or metastasis within 16 months of follow-up. LESSONS: We report a peculiar case of mucous gland adenoma that occurred in the periphery of the lung and involved the parenchyma. The present case reported the smooth muscular bundles presenting in the stroma, which could broaden the histologic profile of the tumor.