Mediastinal Seminoma Workup

Updated: Mar 09, 2020
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Jeffrey C Milliken, MD  more...
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Workup

Laboratory Studies

Routine blood work includes the following:

  • Complete blood count (CBC)
  • Electrolyte concentrations
  • Coagulation profile
  • Renal and liver function tests
  • Lactic dehydrogenase (LDH) levels (known to be elevated and to play a role as a tumor marker)

Alpha-fetoprotein (AFP) and human chorionic gonadotrophin (HCG) levels are usually not elevated in patients with pure seminomas, though approximately 10% may have a slight increase in levels of these tumor markers. Patients with pure seminomas may have only a mild elevation in HCG levels; however, a mixed tumor may be present and cause elevations in AFP levels. If levels of HCG, AFP, or both are elevated, diagnoses other than seminoma should be considered.

Serum low-density lipoprotein (LDL) levels are frequently elevated in patients with seminomas.

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Imaging Studies

Plain radiography

A benign tumor may not be visible on a plain chest radiograph as a mediastinal mass. Usually, the tumor must be sufficiently large in order to show any evidence of mediastinal widening. In 30% of cases, seminomas manifest as coincidental findings. These tumors tend to become quite large before they cause symptoms, yet they do not demonstrate pathognomonic radiographic findings. (See the image below.)

Chest radiograph shows large mediastinal seminoma Chest radiograph shows large mediastinal seminoma causing deviation of trachea.

CT and MRI

Computed tomography (CT) and magnetic resonance imaging (MRI) are useful for determining the precise anatomic relations and morphologic features of the lesion. CT is usually adequate, but MRI may be considered if surgery is a possibility. MRI has better resolution of nearby tissue and vascular invasion.

On CT (see the image below), benign tumors tend to be round masses that grow slowly. They are most commonly located in the superior mediastinum. Calcification may be present but usually is not helpful in the diagnosis, because calcification is also observed in other anterior mediastinal tumors, including thymomas and thyroid goiters. In general, malignant tumors tend to be larger than benign ones, to be lobulated, and to grow faster. CT may also reveal evidence of mediastinal invasion, adenopathy, and metastatic disease in the lungs.

Contrast-enhanced axial CT scan shows ill-defined Contrast-enhanced axial CT scan shows ill-defined anterior mediastinal mass with irregular borders that is infiltrating mediastinal fat. CT-guided needle biopsy revealed mediastinal seminoma.

CT angiography (CTA) is warranted if there is suspicion of superior vena cava syndrome (SVCS).

Ultrasonography

Ultrasonography (US) of the testes is mandatory to ensure that there is no lesion in the scrotum.

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Procedures

Bronchoscopy

Bronchoscopy is indicated if the patient presents with hemoptysis or if there is suspicion of tracheal compresssion.

Biopsy

Needle

In general, tissue diagnosis is necessary even if typical radiologic features are noted or if serum levels of markers are elevated. Percutaneously performed aspiration needle biopsy is the first step. If the tumor is encroaching the trachea or a bronchus, transbronchial biopsy can be performed. A CT-guided needle biopsy is performed if the diagnosis cannot be confirmed with the aspiration needle or transbronchial biopsy.

Cytologic diagnosis is not always sensitive; tissue biopsy is preferred because mediastinal tumors have been diagnosed as lymphomas, which also manifest as bulky lesions in the anterior mediastinum and in persons of the same age range.

Open

Occasionally, a percutaneous technique cannot yield adequate tissue or the mass is in a difficult area; in such cases, an open biopsy is required. Open biopsy is best performed via a small anterior thoracotomy. The procedure is generally accomplished with the patient under general anesthesia, and a small parasternal incision is adequate for most patients.

Strict airway maintenance is required because large anterior mediastinal tumors can compress the trachea and make intubation difficult. A rigid bronchoscopy cart should always be available during this procedure. All anesthesia must be reversed before the patient is extubated. Some patients may require longer intubation times and may be extubated slowly, after the administration of steroids and bronchodilators.

Thoracoscopic

The biopsy can also be performed via thoracoscopy. The thoracoscopic procedure facilitates better evaluation of the tumor and allows biopsy specimens to be taken from multiple sites that are otherwise inaccessible.

Extragonadal workup

Because mediastinal germ cell tumors are not distinguishable from their gonadal counterparts, all extragonadal tissue must be carefully examined.

The histology of a mediastinal seminoma is similar to that of its gonadal counterpart. All patients with biopsy-proven mediastinal seminomas must undergo careful staging with scrotal examination and US, measurement of serum tumor markers, and CT of the abdomen and retroperitoneum.

Blind biopsy of the testes and orchiectomy are not indicated in the workup of seminomas.

Evidence of disease below the diaphragm suggests metastasis. The presence of metastatic disease mandates the use of induction chemotherapy in the management of mediastinal seminomas.

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Histologic Findings

The histopathology of seminoma is illustrated in the image below.

Histopathology of seminoma. Histopathology of seminoma.
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