LIPOID PNEUMONIA IN LUNG-CANCER - RADIOGRAPHIC AND PATHOLOGICAL FEATURES

Background: Obstructive pneumonia, a synonym for endogenous lipoid pne umonia, is often seen in patients with lung cancer, but details of thi s condition are still uncertain. Methods: To elucidate the features of obstructive pneumonia, we radiolopathologically studied 147 patients with lung cancer that had been resected. Results: Gross inspection of the resected materials revealed evidence of endogenous lipoid pneumoni a in 33 of the 147 patients with radiography that corresponded to obst ructive pneumonia. We classified the 33 cases into three types as foll ows: (1) type I lipoid pneumonia, localized to the lung parenchyma dis tal to an airway obstructed by a tumor (23 cases); (2) type II lipoid pneumonia, features of type I lipoid pneumonia and consecutively sprea ding to the adjacent segment whose airway was not affected (five cases ), (3) type III lipoid pneumonia, features of type II lipoid pneumonia and spreading to the isolated segments (five cases). Lipoid pneumonia was found in 16 of 89 (18%) adenocarcinoma cases and in 17 of 55 (31% ) squamous cell carcinoma cases. In type I lipoid pneumonia, squamous cell carcinoma cases were predominant over adenocarcinoma cases (14 vs nine cases), but in type III lipoid pneumonia, adenocarcinoma cases p redominated (four vs one case). Further, in cases of type III lipoid p neumonia, radiographs frequently revealed that lung cancers were cavit ated. Conclusion: Lipoid pneumonia in lung cancer may be associated wi th factors that play a larger role than the cancer alone. It can be sp eculated that transbronchial dissemination of breakdown products of ad enocarcinoma cells, including mucin, may contribute to the spread of t he non-obstructive component of lipoid pneumonia, because the local ph ysical effect of obstructed bronchus does not affect the non-obstructi ve component.