Reappraisal of Endobronchial Polypoid Adenocarcinoma of the Lung

Lung adenocarcinoma rarely presents as a grossly or bronchoscopically visible tumor protruding into the bronchial lumen. This multicenter retrospective study aimed to reappraise this unusual growth pattern, termed endobronchial polypoid adenocarcinoma, and to examine its clinicopathological characteristics. We retrospectively reviewed 2261 surgically resected primary lung adenocarcinomas from 4 institutions and identified 11 cases of endobronchial polypoid adenocarcinoma, accounting for ∼0.5% of the included cases. All tumors showed both pulmonary parenchymal and endobronchial components, and direct continuity between the 2 components through the bronchial wall was identified in 8 cases. A lepidic pattern was observed in the pulmonary parenchymal component in 8 cases. In the involved endobronchial mucosa, abrupt transitions between non-neoplastic ciliated epithelium and adenocarcinoma were identified in all cases. Spread through air spaces was observed in 10 of the 11 cases. EGFR mutations were detected in 3 of 9 examined cases. TTF-1 positivity and NKX3.1 negativity supported a terminal respiratory unit-type rather than bronchial gland-type origin. Postoperative recurrence was observed in 5 patients, with a median time to recurrence of 6 months. Two patients died of the disease. These findings suggest that endobronchial polypoid growth may represent a rare, macroscopically recognizable manifestation of airway-associated progression in lung adenocarcinoma, conceptually related to STAS and endobronchial spreading of adenocarcinoma (EBSA).