Squalene-Induced Extrinsic Lipoid Pneumonia: Serial Radiologic Findings in Nine Patients

Abstract

Squalene-induced extrinsic lipoid pneumonia most commonly appears as areas of ground-glass attenuation mixed with poorly defined centrilobular nodules and crazy paving on CT, being distributed mainly in the right middle and both lower lobes. The lesions are indolent and remain after cessation of squalene ingestion.

Lipoid pneumonia: A challenging diagnosis

“…1 Lipoid pneumonia usually shows significant uptake in [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) and Fluorothymidine-Positron Emission Tomography (FLT-PET) which places it withn the differential diagnosis of lung cancer. 25,28 A histologic examination of the lungs usually detects an accumulation of multiple macrophages with vacuolated foamy cytoplasms in the alveoli, as in our case. 1,4,8,17 With time, proliferative fibrosis occurs, and lipid droplets in varied sizes are trapped extracellularly and surrounded by large, multinucleated, foreign-body giant cells.…”

“…23,24 The most common locations include the right middle lobe, followed by the right lower lobe, the left lower lobe, and the lingula. 10,25 Our patient's lipoid pneumonia affected his right lower lobe (Figures 2, 3).…”

“…This picture in toto is usually termed the "crazy paving pattern." 10,25 This pattern can also be seen in Pneumocystis carinii pneumonia, mucinous bronchioloalveolar carcinoma, pulmonary alveolar proteinosis, sarcoidosis, nonspecific interstitial pneumonia, organizing pneumonia, adult respiratory distress syndrome, pulmonary hemorrhage syndromes, and alveolar microlithiasis. 10,22 Occasionally, oil may coalesce to form large droplets walled by fibrous tissue and giant cells, appearing as tumor-like masses termed paraffinoma.…”

Pneumonia lipoídica em adultos: aspectos na tomografia computadorizada de alta resolução

“…Then, they are incorporated into the alveolar walls, and, through the lymphatic channels, reach the interlobular septa causing its thickening (11,13,14) . The sometimes extensive fibrotic proliferation secondary to repeated aspiration (11,14) , may be associated with a considerable loss of pulmonary volume (15) . Fibrosis may develop and the oil may coalesce, forming large fat drops involved by a fibrotic tissue and giant cells, creating a tumor-like mass called paraffinoma (4) .…”

“…If the diagnosis remains undefined, transbronchial or open biopsy may be required (4) . In conventional radiology, findings of lipoid pneumonia are poorly specific (13) , and the disease alterations appear with variable patterns and distribution (15) . HRCT is the best imaging method for lipoid pneumonia diagnosis (20) .…”