Locally Advanced Thymic Carcinoma With Direct Pericardial Extension and Atrial Clot Diagnosed by Endoscopic Ultrasound

Abstract

Introduction: Thymic carcinoma is a rare malignancy. We report the first case of a locally advanced thymic carcinoma with pericardial involvement and atrial clot diagnosed using endoscopic ultrasound (EUS). Our case highlights the role of EUS in evaluating local disease involvement with rare paraesophageal thoracic malignancies. A 31-year-old white male presented with progressive right posterior and lateral chest pain and hemoptysis for 2 weeks. Past medical history was significant for tobacco use. Chest x-ray revealed right lower lobe consolidation. A confirmatory computed tomography (CT) chest revealed a 5.8 x 4.9 x 4.5-cm subcarinal, oblique paraesophageal mass in the posterior mediastinum engulfing the bronchus intermedius and involving the right lower lobe pulmonary vein and extending to the body of the left atrium. Further work-up with positron emission tomography (PET) scan revealed increased fluorodeoxyglucose (FDG) activity suggestive of malignancy. A CT-guided biopsy of the right lower lobe lung mass basaloid lung carcinoma though thymic carcinoma could not be ruled out. EUS revealed a 4.0 x 4.8-cm mass abutting the left atrium along with a 1.8 x 2.5-cm intra-atrial thrombus. A subcarinal lymph node measuring 3.0 cm x 1.8 cm was also seen. EUS-FNA revealed CAM 5.2, CD 5 positive neoplastic cells. The patient underwent induction chemotherapy followed by right thoracotomy with resection of periesophageal mass, complete thoracic lymphadenectomy, right lower lobectomy, and partial left atriaectomy with subsequent reconstruction of left atrium with myocardial patch. Biopsy from resected tissue showed a lobulated epithelial tumor involving the lung and myocardium. Immunoperoxidase stains were positive for cytokeratin and p63 and negative for CD5, CD57, CD117, CD20, and CAM5.2. Pathologic examination of lung tissue including lymph nodes was consistent with thymic carcinoma. He subsequently underwent concurrent chemoradiotherapy, though chemotherapy had to be discontinued halfway through the treatment course due to increased toxicity. He had complete relief of symptoms and was leading an active life at the time of last follow-up, 2 years after treatment. Follow-up CT scans were negative for any evidence of metastatic disease. We describe the first case of thymic carcinoma with pericardial extension and atrial clot diagnosed under EUS guidance, which can play a major role in diagnosing primary mediastinal malignancies.