A Case of Lipoid Pneumonia Mimicking a Lung Malignancy

Abstract

Introduction: Lipoid pneumonia is an uncommon disease that could mimic infectious or malignant conditions. Clinicians should keep this in their mind while evaluating patients who are at risk of aspiration. We present a case of spiculated lung nodule, thought initially as a lung cancer, was found eventually to be a lipoid pneumonia. Case: A 75-year-old man who is an exsmoker was referred to the thoracic clinic for evaluation of a lung lesion seen on a screening chest X ray. The patient denied any symptoms including cough, sputum production, chest pain, or weight changes. A non-contrast CT chest was obtained, and it showed two left lower lobe spiculated nodules that were suspicious for malignancy. Imaging is shown in figure 1. The nodule density, however, was found to be low (close to fat density on CT) and this is demonstrated in figure 1C. Due to the high risk of malignancy, the patient underwent a left lower lobe wedge resection. Pathology came back showing lipid vacuoles associated with an inflammatory response, lipid-laden foamy macrophages, and scattered foreign body giant cells seen along the airways (Figure 2). No malignant cells were identified. Patient reported drinking a smoothie mixed with olive oil daily for many years. He denied any aspiration symptoms. A diagnosis of exogenous lipoid pneumonia was made. Discussion: It is well known that oil products do not provoke a strong gag or cough reflex leading to chronic silent aspiration of fatty material in exposed patients. The clinical manifestation of this is exogenous lipoid pneumonia. Endogenous lipoid pneumonia, on the other hand, is a much less common condition usually due to fat storage diseases. Obtaining a good history regarding risk factors for aspiration and excessive dietary oil products intake, occupational exposures, or medical use of oil-based products like lip balm and petroleum jelly is essential in the evaluation of such cases. Although the symptoms could be very nonspecific, the radiographic findings of fat attenuation on CT should direct the clinician thinking toward this entity. It can mimic infectious pneumonia, lung fibrosis, or lung malignancy (as happened in our case). Pathology is diagnostic with demonstration of lipid vacuoles and lipid-laden foamy macrophages. Spontaneous resolution is expected with cessation of exposure. However, symptomatic refractory cases may require treatment with glucocorticoids or whole lung lavage.