Objective To elucidate the mechanism of the formation and dissemination of pneumonia type mucinous adenocarcinoma, to improve the diagnostic level of pneumonia type mucinous adenocarcinoma, and to explore the prognosis of the disease. Methods 19 patients with pulmonary mucinous adenocarcinoma were diagnosed by pathology, and the corresponding clinical and pathological data were sorted out. Results 17 patients had cough and expectoration symptoms, 1 patient had no obvious symptoms, 1 patient had cough. The imaging findings included patchy consolidation (100%), ground glass exudation (78.9%), cavity (15.8%), bronchial inflation sign (26.3%), bilateral lung involvement (52.6%), left lower lobe involvement (15.8%) and right lower lobe involvement (15.8%). 73.7% of the patients received chemotherapy after evaluation, 3 cases underwent lobectomy and 1 case targeted therapy. The median overall survival (median OS) was 6 months. Pneumonic mucinous adenocarcinoma may involve multiple lobes and segments of the lung. The effect of anti⁃infective treatment is not good. Ground glass exudation and consolidation are pathologically determined as mucus filling in the alveolar cavity and dissemination of some tumor cells. At the same time, Duff staining of sputum smear showed tumor cells. Conclusion When the imaging findings are ground glass opacity, consolidation, nodules, cavities and dead branches, the possibility of pneumonic lung cancer should be considered. The change of ground glass on imaging needs to be alert to the bronchial lung metastasis caused by the dissemination of adenocarcinoma cells in mucus.