INTRODUCTION: Thymoma is a rare condition that is usually discovered as an incidental finding on chest radiography. We describe a case of a relatively low-grade (B1) thymoma presenting as advanced stage IV disease manifested by Superior Vena Cava (SVC) syndrome and profound anemia.
CASE PRESENTATION: A 34-year old female with no past medical history presented to the emergency department with complaints of severe fatigue, malaise and dyspnea with minimal exertion for the past month. Additionally, she noted chest pain and dizziness with standing, as well as a dry cough and anorexia with a 10-lb weight loss. For the past three years, she has noted progressive distention of the veins in her neck, chest wall and abdomen with some slight fullness in her right neck and face for which she never sought medical attention. On physical exam, she was slightly tachycardic and hypothermic. She appeared weak, pale and cachectic. There was significant distention of the veins in her neck, chest wall and abdomen with slight swelling of her right neck and face. Her lung exam revealed decreased breath sounds on the right side. Her laboratory data revealed a significant normocytic anemia (hemoglobin of 2.5mg/dL) and reticulocytopenia (absolute reticulocyte count of 0.2%). All other chemistries and cell counts were unremarkable. Her chest x-ray revealed a very large mass occupying the right chest with a rim of calcification. Subsequent imaging with computed tomography (CT) of the chest revealed a very large heterogeneous mass with calcifications occupying the right hemithorax and mediastinum with additional right-sided pleural-based nodules and a left upper lobe nodule. The mass was invading and occluding the superior vena cava and prominent collateral vessels were noted in the chest wall. Bronchoscopic evaluation revealed extrinsic compression of the trachea and right mainstem bronchus. Fine-needle aspirates and transbronchial biopsies were non-diagnostic. CT-guided biopsy revealed lymphoepithelial neoplasm most consistent with thymoma (grade B1). Furthermore, bone marrow biopsy revealed very rare erythroid precursors suggestive of pure red cell aplasia. Unfortunately, the tumor was deemed unresectable and the patient is currently undergoing chemotherapy with a cisplatin-based regimen.
DISCUSSIONS: Although thymoma is the most commonly diagnosed anterior mediastinal mass (20%), it is quite rare amongst the general population with an annual incidence of only 0.15 cases per 100,000 adults. Most thymomas are discovered incidentally. Furthermore, only 5% develop an associated paraneoplastic pure red cell aplasia and rarely present as an SVC syndrome. Thymoma is classified by histological grade (World Health Organization [WHO] Classification system) and clinical stage (Masaoka Staging System), both of which have been shown to be good independent predictors of outcome. To our knowledge, it is exceedingly rare for low-grade (B1) thymoma to present with such advanced stage IVa disease. This unfortunate young woman did not seek medical attention for her symptoms of SVC syndrome for three years. Hence, we are provided a glimpse into the natural history of a low-grade invasive thymoma. The relationship between histological grade, clinical stage and development of paraneoplastic syndromes (particularly, pure red cell aplasia) is not well defined.
CONCLUSION: Invasive thymoma is a rare neoplasm that, even with a low histological grade, can present as advanced metastatic and locally invasive disease, including SVC syndrome. Furthermore, the relationship between histological grade, clinical stage and paraneoplastic pure red cell aplasia remains to be defined.
DISCLOSURE: Nidhi Nikhanj, No Financial Disclosure Information; No Product/Research Disclosure Information