Lung Cancer |

Primary Intrapulmonary Thymoma FREE TO VIEW

Steven Hobson, MD; Terence McGarry, MD; Anatoly Leytin, MD
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The Icahn School of Medicine (Elmhurst Hospital), Department of Pulmonary Critical Care Medicine, Elmhurst, NY

Chest. 2014;146(4_MeetingAbstracts):644A. doi:10.1378/chest.1989244
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SESSION TITLE: Cancer Student/Resident Case Report Posters I

SESSION TYPE: Medical Student/Resident Case Report

PRESENTED ON: Tuesday, October 28, 2014 at 01:30 PM - 02:30 PM

INTRODUCTION: Primary intrapulmonary thymomas are rare ectopic thymic epithelial neoplasms with 32 cases reported to date1. Tumors are identified and characterized with various imaging modalities, whereas microscopic morphology and immunohistochemistry provide diagnosis and staging. Treatment involves surgical excision and, if indicated, adjuvant radiation therapy.

CASE PRESENTATION: 46 year old male with no medical history presented with odonyphagia and weight loss. Physical exam revealed oral candidiasis and clear lung fields. He was HIV negative and had no history of taking immunosuppresive therapy. During the next two months, his candidiasis was refractory to antifungal therapy and he lost an additional 14 pounds. Computed tomography (CT) imaging revealed a right-sided 10.5 cm x 7.4 cm x 10.5 cm intrathoracic mass without contrast enhancement in the anterior mediastinum (Figure 1). Fiberoptic bronchoscopy with transbronchial biopsy and cytology was suggestive of T-Cell Lymphoma, and cytology from a CT-guided needle biopsy also suggested lymphoma. Following surgical excision, pathology confirmed an ectopic thymoma, World Health Organization (WHO) Type B1, while the anterior mediastinum was thymic tissue.

DISCUSSION: An ectopic thymoma is a thymic epithelial neoplasm located outside the anterior mediastinal compartment. The mechanism of disease is unsettled with one hypothesis claiming embryologic displacement during the descent of thymic primordia from the third pharyngeal pouch, while another theorizes origin from uncommitted germinative cells. It has been shown to occur across a broad age range and equally affect men and women. Patients typically present with chronic respiratory complaints such as shortness of breath or chest pain, but they may be asymptomatic or have paraneoplastic syndromes. CT imaging may reveal a well demarcated mass or diffuse pleural thickening with lung encasement2. Histology reveals cell nests composed of epithelial cells and small lymphocytes separated by fibrous stroma. Immunohistochemistry stains are positive for Epithelial Membrane Antigen (EMA) and Cytokeratin AE1/AE31.

CONCLUSIONS: Primary intrapulmonary thymomas are rare - this being the 33rd reported case. The current WHO classification system identifies five histologic subtypes that are based on the morphology of the neoplastic epithelial cells and the lymphocyte to epithelial cell ratio3 (Table 1). 5-yr survivability ranges from 90-100% for Stage 1 lesions. Surgical excision is the standard of care and adjuvant radiation should be considered when there is incomplete excision of mass or signs of extracapsular disease as it has been shown to improve 5-yr survival.

Reference #1: Katsura M, et al. Primary Intrapulmonary Thymoma. Gen Thorac Cardiovasc Surg. 2013 Jun 30.

Reference #2: Marom EM. Advances in Thymoma Imaging. J Thorac Imaging 2013;28:69-83.

Reference #3: Girard N, et al. Thymoma: A Focus on Current Therapeutic Management. J Thorac Oncol. 2009;4: 119-126.

DISCLOSURE: The following authors have nothing to disclose: Steven Hobson, Terence McGarry, Anatoly Leytin

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