Glandular papilloma of the lung is one of three histologic types of solitary endobronchial papillomas. It is known as an uncommon benign neoplasm. No malignant glandular papillomas have been reported. Herein, the first case of granular papilloma with malignant transformation is reported. A 74-year-old man with huge right lung mass extended upper and lower lobe was admitted to the hospital complaining of progressive cough and dyspnea. An open lung biopsy was performed. Microscopically, the tumor showed papillary growth pattern with thick fibrovascular cores. The stroma of the fibrovascular cores shown the infiltration of lymphoplasmacytic cells and proliferation of capillaries. The epithelial cells surrounding the papillary fronds were cilliated columnar cells with focal cellar atypia, and frequent mitoses. Suspicious pleural invasion foci were identified. The Ki-67 labeling index was about 24.3% and p53 labeling index was about 31.7%. Glandular papilloma is known as a benign neoplasm, which is lack of atypia and mitosis. In present case, there were several indications of malignant transformation, such as cellular atypia, frequent mitosis, architectural distortion, and pleural invasion. Pathologists must be aware that glandular papilloma can have a changes of malignant transformation. Further studies about disease behavior and molecular characteristics are needed.
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