BACKGROUND
A 59-year-old Hispanic man presents to the emergency department with progressive shortness of breath for 6 months and a new onset of mild chest pain. He has no history of fever, chills, coughing, hemoptysis, weight loss, or smoking. He is otherwise healthy and does not take any medications on a regular basis.
On physical examination, the patient is afebrile with normal vital signs, including an oxygen saturation of 99% while breathing room air. He does not appear to be in acute distress. Cardiovascular examination reveals conjunctival pallor. No evidence of muscle weakness or neurologic deficit is noted. Routine laboratory studies reveal a WBC count of 7200/μL, a hemoglobin level of 10.1 g/dL (101 g/L), a hematocrit of 36% (0.36), and a platelet count of 120,000/μL (120 X 109/L).
The following routine posteroanterior (PA) and lateral chest radiographs are obtained. What is the diagnosis?
Hint
Note the large, lobulated, noncalcified soft-tissue mass in the anterior mediastinum in this older patient who presents with mild chest pain and dyspnea.
ma mai it seems difficult but hope it is not well is it thymoma/lymphoma???????i can think of the most common causes of an anterior mediastinal mass :----- thymoma; teratoma; thyroid disease; & lymphoma [/b]
Thymoma: The patient’s chest radiographs show a lobulated, well-defined, soft-tissue mass in the anterior mediastinum.
A CT scan of the chest not only confirmed these findings but also demonstrated a few hypoattenuating areas, suggesting necrosis or cystic change.
A distinct fat plane was noted between the mass and the mediastinal vascular structures.
The differential diagnosis for this mass includes thymoma (well-defined, smooth mass), lymphoma (ill-defined, lobulated mass with lymphadenopathy in other areas), germ cell tumor (which occurs in patients younger than this patient and which shows cystic areas, fat, and calcification), retrosternal goiter (which should be contiguous with the thyroid gland), and metastatic adenopathy.
A thymoma is the most common primary tumor of the anterior superior mediastinum. It arises from remnant thymic epithelial cells and is usually observed in the fifth to sixth decades of life; its sex predilection is equal in men and women. Thymomas are most commonly encapsulated, locally spreading tumors that can be benign or malignant. They are characterized by their degree of invasiveness.
Three quarters of all thymomas are associated with paraneoplastic syndromes, such as myasthenia gravis (MG), red-cell aplasia, pemphigus, dermatomyositis, systemic lupus erythematous, the syndrome of inappropriate anti-diuretic hormone secretion, and immunoglobulin (Ig) deficiency. Approximately 50% of patients with thymoma have myasthenia, and about 15% of patients with myasthenia have thymoma. A related disorder, Eaton-Lambert syndrome, is also reportedly associated with thymoma. Less than 10% of patients with thymoma have red-cell aplasia, but as many as 50% of those with red-cell aplasia have an associated thymoma, and their condition responds favorably to thymectomy. About 10% of patients with thymoma develop Ig deficiency.
One third of thymoma patients are asymptomatic. The disease may be diagnosed by using routine chest radiographs, which often show mediastinal widening and opacity in the retrosternal, anterior mediastinal space. Another third of patients present with symptoms of compression, such as dyspnea, cough, dysphagia, hoarseness, and chest pain. Hemorrhage may occur in large tumors due to necrosis. The remaining third of patients may present with symptoms suggestive of associated conditions such as myasthenia gravis. Laboratory results are notable for anemia, thrombocytopenia, or neutropenia.
CT scans are usually performed to evaluate the extent of the mass for preoperative planning, to detect local invasion and thoracic and distant metastases, and to guide percutaneous core biopsy. CT and MRI may show cystic change, necrosis, or hemorrhage in the tumor. Nuclear medicine imaging may be done by using thallium-201 (which differentiates normal thymus, lymphoid follicular hyperplasia, and thymoma in patients with myasthenia), indium-111 octreotide, or 18-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET).
Treatment for early, benign, and encapsulated tumors is surgical resection, which is associated with low recurrence rates. Surgically excised samples show the histologic characteristics of the tumor and enables staging to determine the need for adjuvant therapy. Chemotherapy with combinations of etoposide, doxorubicin, cisplatin, and steroids, as well as radiation therapy, are used to manage invasive or metastatic thymoma and incompletely resected or unresectable tumors.
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