SARCOID MASQUERADING AS MALIGNANCY ON IMAGING

Abstract

TOPIC: Imaging TYPE: Medical Student/Resident Case Reports INTRODUCTION: Sarcoidosis is a multi-system inflammatory disease that predominantly affects the lungs and histopathologically characterized by non-caseating granulomas. A comprehensive evaluation must be pursued to diagnose Sarcoidosis as some findings can overlap with other compatible conditions. CASE PRESENTATION: A-44-year-old woman presented with chronic fatigue, shortness of breath, left sided chest pain, and cough. CT chest revealed left hilar, anterior mediastinal, right paratracheal, and subcarinal lymphadenopathy. An 18-F-fluorodeoxyglucose (FDG) positron emission tomography (PET) CT showed extensive mediastinal and hilar PET avid adenopathy. Notable lymph nodes include a 25mm subcarinal node with a Standardized Uptake Value (SUV) of 32.6 and 11mm left hilar node with a SUV of 27.7. The PET CT findings were highly concerning for lymphoma. Patient subsequently underwent an Endobronchial Ultrasound-guided transbronchial needle aspiration of lymph nodes, and forceps biopsy of station 7. Pathology of the lymph nodes was significant for non-caseating granulomas. Ziehl–Neelsen and silver stains were negative for acid fast bacilli and fungi, respectively. Patient was diagnosed with Sarcoidosis and treatment with Methotrexate and folic acid was initiated. Steroids were avoided in the setting of morbid obesity (BMI >40), prediabetes and history of psychiatric disease. DISCUSSION: This case illustrates the potential for misdiagnosis based on high Standardized Uptake Values on FDG PET-CT scan and the value of a comprehensive evaluation involving tissue biopsy. A SUV of >2.5 is suggestive of malignancy however, false positives due to 18-FDG uptake by inflammatory cells in infectious and granulomatous diseases have been reported in a few case series. Sarcoidosis is characterized by non-caseating granulomas that are formed by the recruitment of multiple inflammatory cells such as activated macrophages and lymphocytes which can lead to increased radiotracer uptake. Other causes of granulomatous disease such as fungal and mycobacterial infections, foreign bodies, pneumoconiosis and vasculitis should be explored. Newer nuclear imaging modalities using alternate radio-tracers have been developed to improve specificity however, low accessibility has rendered a paucity of available data. CONCLUSIONS: FDG PET-CT can aid in the detection and monitoring of various pathologies including Sarcoid. Due to the lack of specificity of any one diagnostic evaluation currently, it is important to obtain pathological confirmation in addition to imaging, and rule out other causes of non-caseating granulomas, prior to starting treatment. REFERENCE #1: Anjali Shetty, M., and John D Carter, MD, Sarcoidosis mimicking lymphoma on FDG-PET imaging. Radiology Case Reports 2011. REFERENCE #2: Paul E. Kinahan, P.a.J.W.F., MD, PET/CT Standardized Uptake Values (SUVs) in Clinical Practice and Assessing Response to Therapy. Semin Ultrasound CT MR., 2010. REFERENCE #3: Miyakubo M, Oriuchi N, Tsushima Y, Higuchi T, Koyama K, Arai K, et al. Diagnosis of maxillofacial tumor with L-3-[F-18]-fluoro-alpha-methyltyrosine (FMT) PET: a comparative study with FDG-PET. Ann Nucl Med. 2007. DISCLOSURES: No relevant relationships by Hamna Ahmad, source=Web Response No relevant relationships by Sarah Dubin, source=Web Response No relevant relationships by Ashraf Gohar, source=Web Response No relevant relationships by Sindhuja Palle, source=Web Response