Exogenous lipoid pneumonia: HRCT, MR, and pathologic findings

The objective of this study was to describe high-resolution CT (HRCT) and MR findings of exogenous lipoid pneumonia and to correlate them with pathologic findings. A retrospective review of the medical records of our institution revealed seven patients with a diagnosis of lipoid pneumonia based on clinical data, chest films, bronchoalveolar lavage, and follow-up. Both HRCT and MR imaging were reviewed by two readers. Pathologic examination of the resected specimen or surgical biopsies were also reviewed in the four available cases. The HRCT findings were pulmonary consolidations (n = 6) with fatty (n = 3) or unspecific but low attenuation values (n = 3), areas of ground-glass opacities (n = 5), septal lines, and centrilobular interstitial thickening (n = 5). In five of the seven cases, a crazy-paving pattern of various spread was also present, either isolated (n = 1) or surrounding a pulmonary consolidation. In two cases traction bronchiectasis and cystic changes consistent with fibrosis were seen. At MR imaging (n = 2) a pulmonary consolidation of high signal intensity on T1-weighted image consistent with lipid content was present in one case. Pathologic examination (n = 4) showed the coexistence of lobules with lesions of various ages, sometimes in contiguous lobules, within the same patient. Recent lesions were those with alveolar fill-in by spumous macrophages and almost normal alveolar walls and septae. In more advanced lesions, lobules were filled in with larger vacuoles often surrounded by inflammatory infiltrates of alveolar walls, bronchiolar walls, and septa. The oldest lesions were characterized by fibrosis and parenchymal distortion around large lipid-containing vacuoles. The HRCT findings reflect pathologic findings in exogenous lipoid pneumonia. Although non-specific, consolidation areas of low attenuation values and crazy-paving pattern are frequently associated in exogenous lipoid pneumonia and are indicative of the diagnosis.