A CASE OF LARGE MEDIASTINAL MASS SECONDARY TO HISTOPLASMOSIS

Abstract

SESSION TITLE: Chest Infections 2 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: The differential diagnosis for anterior mediastinal masses classically includes lymphomas and neoplasms of thymus, thyroid, and germ cell origins. Mycotic etiologies such as Histoplasma capsulatum are rare in immunocompetent populations. The following is a pediatric case of a large anterior mediastinal mass secondary to histoplasmosis in an immunocompetent patient. CASE PRESENTATION: A 7-year-old boy with a past medical history of asthma was transferred to the pediatric hematology/oncology service from an outside hospital for evaluation of a paratracheal mass incidentally noted on chest radiograph after presenting with vague abdominal pain, weight loss, and a fever of 38°C.Chest CT revealed calcified pulmonary nodules in the right upper lobe and a 3.1 x 2.7 x 3.7 cm mass with areas of calcification at the confluence of the brachiocephalic veins. Initial workup was targeted towards lymphoma and germ cell neoplasm, but mycotic etiologies were also screened for with serum Cryptococcus antigen and Histoplasma antibody titers that were weakly positive at 1:20 and 1:32 respectively. An M band was present for Histoplasma. The patient had no recent travel to endemic areas, exposure to soil with bird or bat guano, or history of recurrent infections.The mass’s location was not amenable to minimally invasive biopsy. Consequently, pediatric surgery performed a thoracotomy with excisional biopsy of the mass and a right upper lobe wedge resection of the lung nodules. The mass was noted to have caseous drainage upon removal, and intraoperative frozen sections were not concerning for malignancy. Final pathology of the mass and pulmonary nodules revealed lymph node and lung tissue respectively with necrotizing granulomatous inflammation and fungal yeast forms. The fungal stains were compatible with H. capsulatum. Repeat serum Cryptococcus antigen and fungal cultures were negative. He was started on long-term oral itraconazole for 12 weeks. Other than intermittent low fevers, the remainder of hospital course was uneventful. DISCUSSION: H. capsulatum is endemic to the Mississippi, Missouri, and Ohio river valleys and is also commonly found in other temperate climates around the world. The dimorphic fungus preferably grows in soil containing bird or bat guano. Disruption of the soil can lead to inhalation of the mold form’s conidia. An overwhelming majority of pulmonary infections are entirely asymptomatic in immunocompetent patients although <1% of those affected can develop fever, malaise, headache, fatigue, and dry cough which are typically self-limiting. Rarely, as with this case, granulomatous mediastinitis can occur where mediastinal lymph nodes undergo massive enlargement and caseous necrosis. CONCLUSIONS: This process is insidious and the mass can be confused for more common etiologies such as lymphoma in pediatric patients, so it is important to consider mycotic etiologies even in non-endemic areas. Reference #1: Kauffman CA. Histoplasmosis: a clinical and laboratory update. Clin Microbiol Rev. 2007 Jan;20(1):115-32. Reference #2: Shersher DD, Hong E, Breard J, Warren WH, Liptay MJ. Anterior mediastinal mass secondary to histoplasmosis. Ann Thorac Surg. 2012 Jan;93(1):e9-10. DISCLOSURES: No relevant relationships by Narayana Gowda, source=Web Response no disclosure on file for Supriya Gupta; No relevant relationships by jayanth keshavamurthy, source=Web Response No relevant relationships by Daniel Kleven, source=Admin input No relevant relationships by Ivan Morales, source=Web Response no disclosure on file for Gilberto Sostre