Diagnosis: Retrosternal goiter
A retrosternal goiter was the most plausible diagnosis because of the patient’s advanced age, the asymptomatic behavior of the tumor, and its development over several years. The multilobular heterogenous appearance in the CT scan supported this diagnosis and made other disorders, such as thymoma and non-Hodgkin’s disease (to be discussed in a bit) very unlikely. In addition, the noninfiltrative behavior of the tumor suggested a benign mass, and CT images obtained from the neck (not shown) demonstrated that the mass originated from the right thyroid lobe without infiltrative or obstructive growth.
Benign mediastinal goiters are relatively common in adults, and the incidence increases with age.1,2 When a goiter affects adjacent structures or obstructs the trachea, common symptoms include dyspnea, wheezing, coughing, jugular vein compression, dysphagia, vocal cord palsy, phrenic nerve palsy, and Horner’s syndrome.
Differential diagnosis includes thymomas and thymic carcinomas
Masses in the anterior mediastinum comprise a variety of pathologic entities and are more likely to be malignant than masses in other mediastinal compartments.3 The most common lesions are thymomas and thymic carcinomas, lymphomas, germ cell tumors, intrathoracic thyroid or parathyroid lesions, and metastases. Up to 50% of mediastinal tumors are detected incidentally, and cause few—if any—symptoms.4,5
Thymoma and thymic carcinomas represent approximately 20% of the cases of primary anterior mediastinal masses, and can be invasive. In addition, myasthenia gravis or tumor-related syndromes are very suggestive of thymoma.6 CT or magnetic resonance imaging (MRI) studies may help to differentiate the mass in the anterior mediastinum, but histopathological analysis is required to establish a definitive diagnosis.
Lymphomas account for 10% to 20% of primary anterior mediastinal masses. While Hodgkin’s lymphoma predominantly occurs in the third and fourth decade, non-Hodgkin’s disease may affect people at any age.7,8 Most patients are symptomatic at the time of diagnosis, complaining of fever, weight loss, and night sweats. Diagnosis is suggested by a CT scan showing a lobulated mass, but confirmatory histology is necessary to guide treatment and may be accomplished by needle biopsy or lymph node excision on a different body site.
Germ cell tumors represent 15% of anterior mediastinal masses, with an even higher share in children, and include benign teratoma, seminomas, and nonseminomatous germ cell tumors.9 CT and MRI studies may help to clarify the relationship of the tumor tissue to surrounding structures. While teratomas are most likely to occur in children and young adults (and contain various amounts of tissue derived from the ectoderm, endoderm, and mesoderm), seminomas occur predominantly in young men between 20 and 40 years of age (and often have cellular heterogeneity and contain elements of embryonal malignancy).10,11 Seminomas are the most common malignant germ cell tumors, but need to be distinguished from nonseminomatous germ cell tumors; serum levels for alpha-fetoprotein and beta-human chorionic gonadotropin may help, but fine needle aspiration cytology is definitely needed.