Although EGGCTs in adults most commonly present in the mediastinum, primary mediastinal GCTs are still quite rare. In a study of 1,064 patients with mediastinal tumors seen at the Mayo Clinic, malignant GCTs accounted for less than 1% of the tumors in this location while mature teratomas accounted for approximately 8% of cases.35
The majority of patients are symptomatic at diagnosis, with nonspecific symptoms frequently due to a large mass compressing surrounding structures. In one retrospective study of 56 patients, 86% were symptomatic at diagnosis.36 The most common presenting symptoms in this study were chest pain, cough, weight loss, dyspnea, and superior vena cava obstruction. Other series reported similar find ings.937,38 Hemoptysis suggests the presence of embryonal carcinoma or choriocarcinoma.36 37 Often these cases are very advanced at presentation because symptoms do not develop until a large mass is present. In those who are asymptomatic, a mass is often detected incidentally by chest radiography.
Once a primary mediastinal GCT is suspected, staging should include a physical examination, a computed tomography (CT) of the thorax and abdomen, and the measurement of serum tumor markers, including P-hCG, AFP, and lactate dehydrogenase (LDH). Careful examination of the testes is imperative, and testicular ultrasonography is also recommended. CT of the thorax complements chest radiography by helping to define the extent of disease for invasion of crucial structures (Figures 21-5 and 21-6). The presence of elevated levels of serum tumor markers depends on the histology. By definition, pure mature teratoma is marker negative. Although 7 to 10% of seminomas can produce low levels of P-hCG, high levels are highly suggestive of the presence of nonseminomatous elements.39 Elevation of AFP is diagnostic for the presence of non-seminomatous elements and is the tumor marker that is most often elevated in patients with MNSGCTs.10
Although serum tumor markers can sometimes be helpful, diagnosis is ultimately based on histologic review of a tissue sample. Histology is of the utmost importance as both treatment and prognosis vary widely for seminomas and nonseminomas. Often a tumor may contain many histologic types; therefore, a sufficient biopsy specimen is crucial for accurate diagnosis. At times, open surgical biopsy is required to obtain an adequate sample. Table 21-1 summarizes the diagnostic and treatment considerations for a suspected mediastinal GCT.
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