"Mediastinal Masquerade": A Case Of Benign Mediastinal Adenopathy

SESSION TITLE: Medical Student/Resident Disorders of the Mediastinum Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Primary mediastinal amyloidosis localized to the intrathoracic cavity is a rare manifestation of amyloidosis. The diagnosis is challenging, requiring a pathologic diagnosis as well as ruling out the secondary causes. Here we report an uncommon cause of benign mediastinal adenopathy. CASE PRESENTATION: A 53-year-old African American male smoker presented with epigastric pain, tarry stools, and laboratory results indicative of acute pancreatitis. Chest X-ray showed a right perihilar mass with right pleural effusion and CT scan showed multiple large right paratracheal and right hilar nodes with internal calcification. With malignancy being in the differential diagnosis, the patient underwent a fiberoptic bronchoscopy with biopsies which were negative for malignancy. Mediastinoscopy was performed and revealed amyloidosis. Evaluation for multiple myeloma showed elevated kappa and lambda light chains and diffuse polyclonal gammopathy, but there was no monoclonal spike on SPEP. Bone marrow and abdominal fat pad were negative for amyloid, and the patient continues to lack chronic underlying systemic disease with no symptoms on cardiac or pulmonary examination. DISCUSSION: Localized mediastinal primary amyloidosis has been previously reported as a rare condition. Mediastinal amyloidosis is more a diagnosis of exclusion and thus difficult to consider, especially in patients testing negative for multiple myeloma and showing no signs of systemic disease. Diagnosis is challenging, as it can only be done through biopsy and subsequent positive Congo Red staining and apple-green birefringence under polarized light. While the diagnosis has no signature signs, mediastinal calcifications have been noted to occasionally be present, providing reason to consider mediastinal amyloidosis. In most cases, radiological findings conceal the diagnosis, stemming from it mimicking other more common conditions. In the elderly, lung carcinoma is usually higher on the differential, leading to tissue biopsy. While the differential diagnosis of mediastinal adenopathy includes granulomatous lung disease such as sarcoidosis, other causes of secondary amyloidosis such as multiple myeloma need to be excluded. Prognosis for localized amyloidosis is usually good with no specific indication for therapy unless signs of systemic disease begin. CONCLUSIONS: Primary mediastinal amyloidosis remains an uncommon clinical condition. Obtaining a definitive pathologic diagnosis and ruling out causes of secondary amyloidosis remain the standard approach, frequently requiring multiple diagnostic procedures. It may be diagnosed following work up of an incidental finding as was the case in this patient. Reference #1: Bertolino, J., Scemama, U., D’Journo, X. B., Daniel, L., Melenotte, C., Benyamine, A., & Granel, B. (2016). Mediastinal nodular AL-amyloidosis with progressive calcification. QJM: An International Journal of Medicine, 109(10), 683-684. Reference #2: Fiorelli, A., Accardo, M., Ciancia, G., Pettinato, G., & Santini, M. (2014). Isolated mediastinal amyloidosis mimicking a neoplastic lesion. General thoracic and cardiovascular surgery, 62(5), 324-326. Reference #3: Yong, H. S., Woo, O. H., Lee, J. W., Suh, S. I., Oh, Y. W., & Kang, E. Y. (2007). Primary localized amyloidosis manifested as supraclavicular and mediastinal lymphadenopathy. The British journal of radiology, 80(955), e131-e133. DISCLOSURES: No relevant relationships by jayanth keshavamurthy, source=Web Response No relevant relationships by Atul Lodh, source=Web Response No relevant relationships by Rohit Munagala, source=Web Response No relevant relationships by Varsha Taskar, source=Web Response