Lipoid pneumonia in lung cancer: radiographic and pathological features

Obstructive pneumonia, a synonym for endogenous lipoid pneumonia, is often seen in patients with lung cancer, but details of this condition are still uncertain.

To elucidate the features of obstructive pneumonia, we radiopathologically studied 147 patients with lung cancer that had been resected.

Gross inspection of the resected materials revealed evidence of endogenous lipoid pneumonia in 33 of the 147 patients with radiography that corresponded to obstructive pneumonia. We classified the 33 cases into three types as follows: (1) type I lipoid pneumonia, localized to the lung parenchyma distal to an airway obstructed by a tumor (23 cases); (2) type II lipoid pneumonia, features of type I lipoid pneumonia and consecutively spreading 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 predominated (four vs one case). Further, in cases of type III lipoid pneumonia, radiographs frequently revealed that lung cancers were cavitated.

Lipoid pneumonia in lung cancer may be associated with factors that play a larger role than the cancer alone. It can be speculated that transbronchial dissemination of breakdown products of adenocarcinoma cells, including mucin, may contribute to the spread of the non-obstructive component of lipoid pneumonia, because the local physical effect of obstructed bronchus does not affect the non-obstructive component.