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A Rare Case of Thymic Neuroendocrine Tumor Presenting with Generalized Weakness and Dyspnea
Mariam Agladze1, Sakil A. Bhuiyan1, Leno Thomas2
1Internal Medicine, Icahn School of Medicine at Mount Sinai/NYC H+H/Queens, New York, NY, United States. 2Hematology&Oncology, Icahn School of Medicine at Mount Sinai/NYC H+H/Queens, New York, NY, United States.

Purpose of Study: Introduction: Thymic tumors are among the rarest forms of malignancy accounting for 0.13 cases per 100,000 people in the United States. Even rarer is its subgroup, thymic neuroendocrine tumor (NET). Here we discuss a rare case of Adrenocorticotropic hormone (ACTH) secreting Thymic NET.
Case Presentation: A 38-year-old male with no past medical history presented with generalized weakness and dyspnea for 1 month. He was found to have hypokalemia at 2.4 mmoL/L and metabolic alkalosis. Chest X-ray and CT chest revealed anterior mediastinal mass measuring 9x10.3x6.1 cm(Image 1; 2). Further workup showed elevated morning serum cortisol and ACTH levels, no response to high dose dexamethasone suppression, absolute CD4 count of 98, negative HIV test, normal metanephrine, acetylcholine binding antibody, and human chorionic gonadotropin levels. Biopsy of mass was reported as a grade 2 neuroendocrine tumor atypical carcinoid variety, positive for cytokeratin AE1/E3, Cam 5.2, synaptophysin, chromogranin, and ACTH and negative for CK7. The patient eventually underwent complete thymectomy and mediastinal mass resection with lymph node dissection.

Methods Used:

Summary of Results:
Discussion: Presenting symptoms of Thymic NET can include cough, dyspnea, superior vena cava syndrome (20%), or hoarseness. Thymic NET rarely presents with paraneoplastic syndromes such as carcinoid, acromegaly, SIADH with the most common being Cushing's syndrome. Few cases are reported in literature with Thymic NET associated with Cushing's syndrome presenting with cushingoid appearance, hyperpigmentation, facial fullness, plethora as well as weakness. Thymic NET was also reportedly observed in males with 65% 5-year mortality rate with associated paraneoplastic syndromes compared to 35% without it. The mainstay of treatment is surgical resection, even in advanced stages, as it is a strong predictor of overall survival. There is no drug regime proven to have a consistent response, although adjuvant chemotherapy regimen (etoposide and cisplatin, and 5-fluorouracil) have been tried.

In conclusion, Thymic NET is a rare tumor with an aggressive course. Further studies need to be done to investigate the early diagnosis of thymic tumors. Surgical resection is the mainstay of treatment. Effective chemotherapy regimens need to be investigated for the optimal management of thymic NET.

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