In a case recently observed occlusion of a segmental bronchus by inspissated mucus produced large bronchiectatic abscesses radiographically demonstrable as a mass resembling a neoplasm. The severe, chronic inflammatory process produced cytologic changes of metaplasia, atypical enough to be interpreted as malignant, probably adenocarcinoma of the lung. Case Report P. R., a 20-year-old vigorous female college student, was admitted to St. Paul Hospital, Dallas, Texas, with pain in the left anterior chest of four weeks duration. There was no history of fever, weight loss, or fatigue accompanying the current illness. The patient was a non-smoker. The past history revealed that she had suffered from asthma “for most of her life,” had experienced frequent respiratory infections accompanied by a productive cough, and had had pneumonia one and two years before the present episodes. Chest films on these occasions were reportedly negative. Physical Examination and Admission Laboratory Data: The patient was a well developed girl in no distress, but with a brassy cough. The only positive findings were expiratory squeaks and wheezes in the left anterior lower thorax, and dullness to percussion outside the left midclavicu1ar line in the fifth intercostal space. Breath sounds were of bronchial quality in this area. Skin tests for blastomycosis, histoplasmosis, and coccidioidomycosis, and with second-strength purified protein derivatives (P.P.D.) for tuberculosis were negative at thirty-six hours. Roentgen Findings: Review of the chest films taken at college just prior to admission and during the current illness revealed a large, lobulated density in the left hemithorax, obscuring the left cardiac border and occupying the lingula division of the left upper lobe. The mass measured approximately 9 × 6 × 7 cm. On the right was a small, poorly defined, somewhat linear infiltrate in the right upper lobe between the second and third ribs anteriorly. Admission roentgenograms of the chest (Fig. 1) in the postero-anterior and left lateral projections demonstrated the same findings as the pre-admission films. There was associated enlargement of the left hilus but no evidence of pleural effusion or atelectasis. Laminagrams of the chest confirmed these impressions and yielded no additional information. Bilateral bronchography demonstrated a complete block of the inferior segmental bronchus of the lingula division (Fig. 2). The lobulated mass occupied the lingula division, displaced the left upper lobe bronchi superiorly, and compressed the left lower lobe bronchi. No evidence of bronchiectasis was obtained. There was nonfilling of the posterior segmental bronchus of the right upper lobe associated with the previously noted linear density. The roentgen diagnosis was tumor of the lingula division and residual pneumonitis in the right upper lobe. Mucoid impaction was considered as the second possibility for both lesions.