[Exogenous lipid pneumonia]

Exogenous lipid pneumonia is an underdiagnosed pathology due to acute or chronic inhalation of lipid substances (paraffin oil, nasal drops, etc.). The clinical and CT appearance is polymorphic, ranging from fibrosing interstitial lung disease to a pseudo-tumoral nodule. The key to CT diagnosis is fatty hypodensity within condensations. The key to histopathological diagnosis is the presence of macrovacuoles in the macrophages, Oil-red-O+(on fresh/frozen material). The differential diagnosis is represented by endogenous lipid pneumonia, common and associated with bronchial obstruction, with necrotic changes, and specific entities such as alveolar proteinosis, hoarding (Niemann-Pick disease) or cordarone treatment.