Rare Case of Thymoma Metastasizing to the Liver as an Incidental Finding

Document Type

Conference Proceeding

Publication Date

10-1-2024

Publication Title

Am J Gastroenterol

Abstract

Introduction: Thymomas are the most common anterior mediastinal mass but make up less than 1.5% of adult malignancies. The occurrence is 0.13 cases per 100,000 person-years. The 2021 WHO classification includes 6 types: A, AB, B1-3 and thymic carcinoma. Staging is based on tumor capsule invasion, locoregional spread, lymph node involvement, and distant metastasis. They can present asymptomatically or with paraneoplastic syndromes, like Myasthenia Gravis. They carry malignant potential regardless of type or stage and can recur despite resection. The 5-year survival for nonresectable metastatic disease is 24%. We present a case of an asymptomatic thymoma with rare, isolated liver metastasis that was identified incidentally Case Description/Methods: An 89-year-old man presented with acute urinary retention, attributed to benign prostatic hyperplasia (BPH). CT imaging revealed a significantly enlarged prostate ( .10 cm). He had previously declined treatment for BPH. Incidental imaging findings included a 1.9 cm lesion in the left hepatic lobe and a 6.8 x 5.2 cm mass in the aortopulmonary window. Subsequent CT chest showed a left anterior mediastinal mass, and biopsies confirmed malignant thymoma with Type B2 features. An MRI of the abdomen redemonstrated the hepatic mass, which grew 1.3 cm over 4 years. Endoscopic ultrasound (EUS) guided biopsy of the liver confirmed metastatic thymoma. PET-CT did not suggest other metastatic sites. Thoracic tumor board recommended radiation to the primary site and liver. Systemic chemotherapy and surgery were not advised due to his age, social support, and functional status. He completed 30 fractions of radiation to the mediastinum and 3 of 5 fractions to the liver. He continues to require a chronic foley catheter for BPH Discussion: We present a rare case of metastatic B2 thymoma isolated to the liver, identified only in 3 other reports. A 2023 review found only 39 cases of extra-thoracic thymoma metastasis, with 12 involving the liver; 5 were types B1 or B2 and liver was the only site in 3 cases. Thymomas often spread locally within the mediastinum, with rare distant metastasis. Extra-thoracic metastasis occurs in 3-6% of cases Despite surgical resection, recurrence rates vary, and prognosis can be poor. Given the unpredictable nature of thymomas, close surveillance with regular CT or MRI is recommended. Advanced endoscopy could also play a role in monitoring and diagnostic for indeterminate findings (see Figure 1).

Volume

119

Issue

10

First Page

S2847

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