False positive 18FDG PET-CT results due to exogenous lipoid pneumonia secondary to oily drug inhalation: A case report

Pattern of FDG-PET uptake in lipoid pneumonia simulating lung cancer

Lipoid pneumonia presents with a variety of lung abnormalities, particularly mass forming lesions that mimic lung cancers. While ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) is expected to discriminate both diseases, some previous reports showed pseudo-positive FDG uptake in lipoid pneumonia. Here, we report a case of pathologically proven chronic lipoid pneumonia in a 78-year-old Japanese man. Computed tomography (CT) showed multi-lobar mass-forming lesions with a fat-density. PET confirmed the spotty accumulation of FDG in the corresponding fat-density area on CT, suggesting lipoid pneumonia. We reviewed the literature and discussed the FDG uptake patterns in lipoid pneumonia.

Exogenous lipoid pneumonia: when radiologist makes the difference

PURPOSE

To report high-resolution CT (HRCT) findings in our group of patients with exogenous lipoid pneumonia (ELP), confirmed with histopathological findings and clinical-anamnestic data, in order to describe the most common radiological patterns of this rare disorder.

MATERIALS AND METHODS

In this retrospective study, HRCT of 10 patients with ELP were evaluated by three radiologists. Diagnosis of ELP was made through CT, bronchiolo-alveolar lavage (BAL) and a pneumological examination associated with an accurate medical anamnesis. Five patients had a histologically proven ELP, through lung biopsy. All patients had a chronic exposition to substances made of animal fat or mineral/vegetable oils.

RESULTS

In our cohort of patients with ELP, the following parenchymal patterns were observed: 8/10 patients had lung consolidation with adipose density (attenuation values < - 40 HU); 10/10 patients had multiple areas of ground glass opacity; 6/10 patients had smooth thickening of interlobular septa and ground glass opacities ("crazy-paving" pattern); 2/10 patients presented nodules > 2.5 cm with spiculated margins (tumor-like); 5/10 patients showed reactive lymph nodes enlargement. The oldest lesions were characterized by bronchiectasis and fibrosis around the lipidic consolidations.

CONCLUSION

Pulmonary alterations found in HRCT exams can be confused with other lung diseases (especially lung tumors) and they are always a challenge even for the most experienced radiologist. In our experience, although non-specific, consolidation areas with low HU values and crazy-paving pattern are frequently associated in ELP. These characteristics should alert the radiologist to consider ELP among the possible differential diagnoses, always correlating the results of CT examination with appropriate clinical-laboratory evaluations and an accurate anamnesis.

A case report of exogenous lipoid pneumonia associated with avocado/soybean unsaponifiables

BACKGROUND

Exogenous lipoid pneumonia is a rare disease resulting from intra-alveolar accumulation of lipids of mineral, vegetal, or animal origin, that induce a foreign body type of inflammatory reaction in the lungs. Gastroesophageal reflux disease and other esophageal abnormalities have often been associated with this disease.

CASE PRESENTATION

We herein report the case of an 83-year-old patient in whom a follow-up chest computed tomography scan, for a lingular consolidation, showed multifocal ground glass and consolidative opacities with areas of low attenuation, suggestive of exogenous lipid pneumonia. The patient had been on piascledine capsules (avocado/soybean unsaponifiables) for 20 years and had a hiatal hernia with documented gastroesophageal reflux disease. After thorough history taking, no other predisposing factors were found. The diagnosis was confirmed using oil red staining of bronchoalveolar lavage showing lipid-laden macrophages and extracellular lipid droplets.

CONCLUSIONS

To our knowledge, this is the first case of ELP secondary to avocado/soybean unsaponifiables in the literature.

Increased FDG Uptake and Chronic Lung Changes in a Case of Persistent Lipoid Pneumonia

Lipoid pneumonia is uncommon disease caused by presence of macroscopic fat in the lung parenchyma commonly originating from exogenous source secondary to aspiration or inhalation of animal fats or mineral or vegetable oils. Alternatively, it can be due to endogenous fat accumulated in the alveoli in the setting of chronic bronchial obstruction or inflammation. The imaging findings include ground-glass opacities, consolidation, nodules, and masses. Presence of macroscopic fat on CT is helpful; however it might not always be present. Increased FDG uptake can be present secondary to ongoing inflammation mimicking malignancy. Tissue diagnosis might be needed in some cases.

Erratum: False positive 18FDG PET-CT results due to exogenous lipoid pneumonia secondary to oily drug inhalation: A case report: Erratum

[This corrects the article DOI: 10.1097/MD.0000000000006889.].