False-positive FDG-PET scan secondary to lipoid pneumonia mimicking a solid pulmonary nodule

A rare case of lipoid pneumonia mimicking lung malignancy on radiological imaging: A case report

Lipoid pneumonia is a rare benign lung disease pathologically characterized by the presence of lipids in the alveoli. It may mimic lung malignancy on radiological imaging. In this case report we present a case of lipoid pneumonia that radiologically manifested as a lung mass and summarize the typical investigation findings and the management of the disease from the literature review to serve as a reminder of and refresh our knowledge of this rare disease entity.

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.

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.

Adult exogenous lipoid pneumonia: A rare and underrecognized entity in cytology - A case series

Background:

Exogenous lipoid pneumonia (ELP) is a rare benign entity without specific clinical or imaging presentation. Although cytological studies – either bronchoalveolar lavage (BAL) or fine-needle aspiration (FNA) – may be pursued in patients with ELP, a definitive diagnosis is frequently rendered only on histology. The aim of this study is to highlight the cytological features of ELP.

Methods:

A search of cytopathology (CP) and surgical pathology (SP) diagnoses of ELP was conducted. The corresponding clinical and imaging features were obtained, and the morphology, particularly the presence and size of the intracytoplasmic vacuoles and background, was assessed.

Results:

Nine cases of ELP were identified, including eight with corresponding CP and SP. A neoplasm was suspected in three based on imaging, but ELP was not in the differential clinically or radiographically in any. Among the cases, six patients had BALs and three FNAs. All of the samples showed multiple large vacuoles within macrophages with at least some equal to or larger than the size of the cell nucleus. Similar vacuoles were noted extracellularly on smears.

Conclusions:

ELP is typically described in case reports in the clinical or radiological literature. To the best of our knowledge, this represents the largest series of adult ELP in CP. When large vacuoles are present in macrophages in cytology specimens, at least a suspicion of ELP can be suggested to initiate appropriate therapy, identify/remove the inciting agent, and preclude a more invasive procedure.

A Unique Case of Pulmonary Hyalinizing Granuloma Associated With FDG-avid PET Scan and Deep Venous Thrombosis

An 83-year-old obese woman with a 60-pack-year smoking history was referred for evaluation of an abnormal chest radiograph [chest x-ray (CXR)]. Her past medical history was significant for recurrent deep venous thrombosis without any predisposing factors. CXR showed a large mass in the right mid lung and another nodule at the right apex, highly suspicious for a neoplastic process. These were not present on a CXR from 2 years earlier. An fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) scan revealed that all lesions were strongly FDG-avid. Six CT-guided core-needle lung biopsy specimens were obtained from the lung mass and all contained dense, lamellar, or "ropy" keloid-like collagen bundles arranged in a haphazard pattern. The biopsy specimens lacked significant necrosis and granulomas. Congo red stain with polarization was also negative for amyloid. The diagnosis of pulmonary hyalinizing granuloma (PHG) was made. A complete hypercoagulable workup was performed but no underlying abnormalities were found, including a negative lupus anticoagulant and malignancy workup. The patient was maintained on warfarin and followed with serial CT scans for 1 year, with spontaneous regression in the lung mass. The case is unique as it is the first case that reports an association of PHG with recurrent deep venous thrombosis in the absence of autoimmune or procoagulant factors and emphasizes the need for life-long anticoagulation in such scenarios. Also, we report the FDG-avid PET scan findings here that are novel for this disease in adults and add PHG to the list of diseases causing false-positive PET scans when malignancy is suspected.

Impact of 18F-FDG PET scan on the prevalence of benign thoracic lesions at surgical resection

OBJECTIVE: The main utility of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) lies in the staging of lung cancer. However, it can also be used to differentiate indeterminate pulmonary lesions, but its impact on the resection of benign lesions at surgery is unknown. The aim of this study was to compare the prevalence of benign lesions at thoracotomy carried out for suspected lung cancer, before and after the introduction of PET scanning in a large thoracic surgical centre. MATERIALS AND METHODS: We reviewed our prospectively recorded surgical database for all consecutive patients undergoing thoracotomy for suspected or proven lung cancer and compared the prevalence of benign lesions in 2 consecutive 2-year groups, before (group I) and after (group II) the introduction of FDG-PET scan respectively. RESULTS: Surgical resection was performed on 1233 patients during the study period. The prevalence of benign lesions at surgery in groups I and II was similar (44/626 and 41/607, both 7%), and also in group II between those who underwent FDG-PET scan and the remainder (21/301 and 20/306 respectively, both 7%). In group II, of the 21 patients with benign lesions, who underwent FDG-PET, 19 had a false positive scan (mean standardised uptake value 5.3 [range 2.6-12.7]). Of these, 13 and 4 patients respectively had non-diagnostic bronchoscopy and percutaneous transthoracic lung biopsy pre thoracotomy. There was no difference in the proportion of different benign lesions resected between group I and those with FDG-PET in group II. CONCLUSION: The introduction of FDG-PET scanning has not altered the proportion of patients undergoing thoracotomy for ultimately benign lesions, mainly due to the avidity for the isotope of some non-malignant lesions. Such false positive results need to be considered when patients with unconfirmed lung cancer are contemplated for surgical resection.

Lipoid pneumonia: a challenging diagnosis

Lipoid pneumonia is a rare medical condition, and is usually classified into two groups, ie, exogenous or endogenous, depending on the source of lipids found in the lungs. Exogenous lipoid pneumonia may result from the aspiration of food and lipids. Although most cases are asymptomatic, common symptoms include cough, dyspnea, chest pain, pleural effusions, fever, and hemoptysis. Radiologically, lipoid pneumonia can manifest as consolidations, pulmonary nodules, or soft-tissue densities. These presentations involve a wide differential diagnosis, including lung cancer. Other rare causes of fatty pulmonary lesions include hamartomas, lipomas, and liposarcomas. The avoidance of further exposures and the use of corticosteroids, antibiotics, and lavage comprise the mainstays of treatment. The exclusion of mycobacterial infections is important during diagnosis, in view of their known association. Generally, acute presentations run a benign course, if promptly treated. Chronic cases are more persistent and difficult to treat. Although the radiologic and pathologic diagnosis is fairly reliable, more research is needed to clarify the optimal treatment and expected outcomes. We report on a 54-year-old man presenting with progressively worsening cough, hemoptysis, and dyspnea over a few weeks. The patient underwent multiple computed tomographies of the chest and bronchoscopies. All failed to diagnose lipoid pneumonia. The diagnosis was finally established using video-assisted thoracoscopic surgery. Most of the paraffinoma was resected during this surgery. He was treated with antibiotics and steroids, and discharged from the hospital in stable condition.

Contrast-enhanced ultrasonography in nodular splenomegaly associated with type B Niemann-Pick disease: an atypical hemangioma enhancement pattern

INTRODUCTION

Niemann-Pick disease (NPD) types A and B are lipid storage disorders. NPD type A is a fatal disorder of infancy. Type B is a non-neuronopathic form observed in children and adults. It is associated with enlargement of the liver, spleen, or both, and nodular splenomegaly may be detected with ultrasound.

METHODS

A 21-year-old female was admitted to the Emergency Room with fever, pharyngitis, and left upper quadrant abdominal pain. Labwork revealed anemia, thrombocytopenia, increased levels of AST, ALT, GGT, AF, LDH, triglycerides, and total cholesterol and low levels of HDL-cholesterol. PCR blood assays for CMV and EBV were both negative. Chest X-ray was unremarkable. Transabdominal B-mode ultrasound (US) revealed splenomegaly (long axis: >22 cm), an irregular subcapsular hypoechoic lesion in the superior pole that was consistent with splenic infarction, and multiple round highly echogenic nodes measuring 1-5 cm in diameter. Contrast-enhanced ultrasonography (CEUS) was performed using SonoVue(®) (Bracco).

RESULTS

The presence of a splenic infarction was confirmed. The nodular lesions showed arterial-phase enhancement with late parenchymal phase wash-out. (18)F-FDG-PET revealed splenic nodular uptake. Primary splenic lymphoma was suspected, and the patient underwent open splenectomy. The diagnosis was type B NPD with splenic hemangiomas.

DISCUSSION

CEUS confirmed the diagnosis and extent of splenic infarction, but the nodular atypical enhancement pattern together with nodular (18)F-FDG-PET uptake was misleading, suggesting as it did lymphoproliferative involvement of the spleen.