A 40-year-old Caucasian woman presents with an abnormal chest x-ray as part of a preoperative work-up for a minor gynecological procedure. Each of the following lesions is consistent with the CT scan shown EXCEPT

A. lymphoma
B. Schwannoma
C. substernal goiter
D. teratoma
E. thymoma

Answer C

The most common lesions found in the anterior mediastinum include lymphoma, substernal goiter, teratoma, and thymoma. Lymphomas are ubiquitous in the mediastinum and can occur in all the mediastinal compartments, although they tend to occur predominantly in the anterior and middle mediastinum. These lesions can be visualized discretely by chest x-ray and CT scan. Biopsy of these lesions is diagnostic, and no therapeutic resection is necessary. Currently, needle biopsy techniques with flow cytometry and molecular biological markers are used in some institutions. Otherwise, a formal surgical biopsy is required to identify the subtype of Hodgkin's from non-Hodgkin's lymphoma.

Schwannomas are posterior mediastinal tumors typified by a paravertebral mass in relationship to one of the intercostal nerve bundles.

Substernal goiters are common anterior/superior mediastinal masses. These can usually be identified using a CT scan. The scan should be performed without iodinated contrast if substernal goiter is suspected, since this will interfere with iodine uptake scan. Often there will be highlighting of the iodine-enhanced goiter even before contrast is given. Likewise, one can perform a nuclear medicine scan to identify active thyroid tissue in the anomalous position before or following the non-contrast CT scan. These lesions can usually be approached by a cervical incision; resection is curative.

Teratomas and germ cell tumors are found in the anterior mediastinum. Teratomas are usually benign (dermoid tumors) and should be resected. Malignant germ cell tumors (seminomas, teratocarcinomas, embryonal cell carcinomas, choriocarcinoma) are identified by elevated serum markers and diagnosis is confirmed by needle biopsy. These tumors are treated with a combination of chemotherapy and radiation therapy possibly followed by surgery.

Thymomas are the most common anterior mediastinal tumor. Resection is indicated in most patients for treatment and cure. In patients with myasthenia gravis the incidence of thymoma is 10-15%.