P3106 - Rare Case of Thymoma Metastasizing to the Liver as an Incidental Finding

Polo Kostecki, DO¹, Diana Jomaa, MD², Robert Pompa, MD^2
1Henry Ford Hospital, Detroit, MI; ²Henry Ford Health, Detroit, MI

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 six 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 male 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 four 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 three other reports. A 2023 review found only 39 cases of extra-thoracic thymoma metastasis, with 12 involving the liver; five were types B1 or B2, and liver was the only site in three 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.



Disclosures:


Polo Kostecki, DO¹, Diana Jomaa, MD², Robert Pompa, MD². P3106 - Rare Case of Thymoma Metastasizing to the Liver as an Incidental Finding, ACG 2024 Annual Scientific Meeting Abstracts. Philadelphia, PA: American College of Gastroenterology.