A 21-year-old man comes to the emergency department due to a 6-week history of progressive shortness of breath and cough. The patient wheezes at night and has to sit up to relieve the chest discomfort. He has no other medical conditions. He takes no medications. The patient denies the use of tobacco, alcohol, and illicit drugs. Temperature is 36.1 C (97 F), blood pressure is 120/70 mm Hg, pulse is 70/min, and respirations are 14/min. Pulse oximetry is 98% on room air. The patient is awake, alert, and in no distress. No masses are palpable in the neck. Heart and lungs sounds are normal. CT scan of the chest reveals a large, anterior mediastinal mass causing tracheal compression. Serum levels of alpha fetoprotein and β-hCG are elevated. Which of the following is the most likely diagnosis?

Question

A 21-year-old man comes to the emergency department due to a 6-week history of progressive shortness of breath and cough.  The patient wheezes at night and has to sit up to relieve the chest discomfort.  He has no other medical conditions.  He takes no medications.  The patient denies the use of tobacco, alcohol, and illicit drugs.  Temperature is 36.1 C (97 F), blood pressure is 120/70 mm Hg, pulse is 70/min, and respirations are 14/min.  Pulse oximetry is 98% on room air.  The patient is awake, alert, and in no distress.  No masses are palpable in the neck.  Heart and lungs sounds are normal.  CT scan of the chest reveals a large, anterior mediastinal mass causing tracheal compression.  Serum levels of alpha fetoprotein and β-hCG are elevated.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

Explanation: This patient has a large, anterior mediastinal mass that is causing cough, shortness of breath, and postural wheezing due to mass-effect compression of other mediastinal structures, including the trachea. The differential diagnosis of anterior mediastinal masses includes the 4 Ts: thymoma, teratoma (and other germ cell tumors [GCTs]), "terrible" lymphoma, and thyroid neoplasm. When serum hormone levels of alpha fetoprotein (AFP) and β-hCG are elevated, a malignant GCT is likely. differential diagnosis Malignant GCTs occur predominantly in young men and can usually be distinguished by differences in serum hormone levels: Seminomas, which are more common than nonseminomatous GCTs, may cause elevated serum β-hCG in a minority of cases, but AFP is almost always normal (Choice C). Nonseminomatous GCTs, which include yolk sac tumors, choriocarcinoma, embryonal carcinoma, and mixed GCTs that contain a mixture of different cell types, cause an elevated AFP and/or β-hCG in the majority (~85%) of patients. In contrast, benign teratomas of the mediastinum typically do not cause elevation of either AFP or β-hCG. They can also often be distinguished from other GCTs on imaging by the presence of fat, bone, or fluid. Biopsy is typically performed to confirm the diagnosis prior to treatment. In addition, testicular ultrasound is performed to determine whether a primary testicular tumor is present because management and prognosis differ among primary mediastinal and metastatic (eg, testicular) GCTs. (Choice A) Lymphoma can arise in any of the mediastinal compartments, including the anterior mediastinum. However, it is not associated with elevated β-hCG and AFP. In addition, patients with high-grade (ie, fast-growing) lymphoma often have systemic symptoms (eg, fever, weight loss, night sweats). (Choice D) Small cell neuroendocrine tumors may present as a lung mass, but an isolated anterior mediastinal mass would be unusual. (Choice E) Thymomas are a common cause of anterior mediastinal masses. However, they do not cause elevated β-hCG and AFP. In addition, they usually occur in middle-aged patients and often lead to paraneoplastic syndromes such as myasthenia gravis (with abnormal levels of anti-acetylcholine receptor antibodies). Educational objective: The differential diagnosis for anterior mediastinal mass includes the 4 Ts: thymoma, teratoma (and other germ cell tumors), "terrible" lymphoma, and thyroid neoplasm. Seminomas may cause elevated β-hCG, but alpha fetoprotein (AFP) is essentially always normal. In contrast, most nonseminomatous germ cell tumors cause elevated AFP and/or β-hCG. References: Approaching the patient with an anterior mediastinal mass: a guide for clinicians. (http://www.ncbi.nlm.nih.gov/pubmed/25396306)

A 21-Year-Old Man Comes to the Emergency Department Due to a 6-Week