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Signs and Symptoms of Chest Diseases |

False-Positive PET Scan in a Patient With Lipoid Pneumonia Simulating Malignancy

Juan Enghelmayer, MD; Tulio Papucci, MD; Luciano Melatini, MD; Julio Silio, MD
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Hospital de Clínicas José de San Martín, Buenos Aires, Argentina


Chest. 2013;144(4_MeetingAbstracts):936A. doi:10.1378/chest.1699499
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Abstract

SESSION TITLE: Miscellaneous Global Case Reports

SESSION TYPE: Global Case Report

PRESENTED ON: Tuesday, October 29, 2013 at 01:30 PM - 02:30 PM

INTRODUCTION: Positron emission tomography (PET) scanning is useful in evaluating suspicious lesions of the lung. Lipoid pneumonia ( LP) usually presents with pulmonary opacities or as a nonresolving process. We report a case of lipoid pneumonia that presented as a solitary pulmonary nodule and had a high standard uptake value on PET scan, thereby mimicking a malignant process.

CASE PRESENTATION: We present a 66 year old woman, with a history of hypertension, obesity, hypothyroid, former smoker (30 p / y), consulting for 6 months of productive cough. Physical examination showed few rhonchi at right base. Normal Blood tests, lung function tests with spirometry, lung volumes and carbon monoxide diffusing capacity (DLCO) normal. ChestTomography (CT) evidenced a 3 cm opacity in the right lower lobe. PET scan showed an hypermetabolic opacity in medial segment of the right lower lobe, with irregular borders and reach SUV max of 2.8. Thoracoscopic biopsy was performed and histopathology showed mediastinal lymph nodes with pigmented macrophages. Areas of consolidation and loss of architecture with accumulations of multinucleated macrophages , and numerous intracytoplasmic lipid vacuoles of variable size. Lymphocytic infiltrate and few fibroblasts, findings consistent with lipoid pneumonia , confirmed the diagnosis. Later, liquid vaseline intake for chronic constipation was observed.

DISCUSSION: Exogenous lipoid pneumonia is usually encountered in 2 situations: ingestion of vaselin for chronic constipation and use of oily nasal preparations for rhinopharyngeal obstruction. These oily substances are mineral oils and are not cleared by the lungs. In the LP, lack of characteristic clinical or radiological profiles can cause a delay in the recognition of the disease. Most patients with lipoid pneumonia present with fever, cough, dyspnea, or crepitations. In many patients, the finding could be incidental as in our patient. Lung function is usually normal or could show a restrictive pattern with decreased DLCO. Diagnosis can be established by demonstrating lipid-laden macrophages in the sputum, bronchoalveolar lavage (BAL) or lung biopsy. Importantly, progression can be stopped by avoiding exposure to irritants. LP can result in a variety of patterns on high-resolution CT scan, including ground-glass opacities, consolidation, thickening of interlobular septa with or without parenchymal distortion, and the crazy-paving pattern. It is very important to consider that this entity along with other inflammatory / infectious diseases such as tuberculosis, histoplasmosis, sarcoidosis, aspergillosis and pulmonary embolism are causes of glucose uptake in PET-CT, called "false positives" of this method. The treatment consists of preventing any further intake and correcting the underlying condition, if possible.

CONCLUSIONS: Lipoid pneumonia can present as a PET-positive lung nodule and should be considered in the differential diagnosis of a solitary pulmonary nodule.

Reference #1: Talwar A, Mayerhoff R, et al. False-positive PET scan in a patient with lipoid pneumonia simulating lung cancer. Clin Nucl Med. 2004 Jul;29(7):426-8.

Reference #2: Gondouin A, Manzoni P, Ranfaing E, et al. Exogenous lipid pneumonia: a retrospective multicentre study of 44 cases in France. Eur Respir J. 1996;9:1463.

Reference #3: Laurent F, Philippe JCS, Vergier B, et al. Exogenous lipoid pneumonia: HRCT, MR, and pathologic findings. Eur Radiol. 1999;9:1190.

DISCLOSURE: The following authors have nothing to disclose: Juan Enghelmayer, Tulio Papucci, Luciano Melatini, Julio Silio

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