Learning Radiology xray montage

Mediastinal Teratoma

  • Mediastinum is a rare site for occurrence of teratomas, most being ovarian in origin
  • Arise from primitive germ cell rests
    • Supposed to migrate along urogenital ridge to primitive gonad
    • Journey is interrupted in the mediastinum
  • May be solid or cystic
    • Most are cystic
  • Three major categories
    • Mature teratomas
      • Well-delineated from surrounding tissues
      • Contain ectodermal elements along with cartilage, fat and smooth muscle
    • Immature teratomas
      • Same elements as above with primitive tissues found in fetus
    • Teratomas with malignant transformation
      • Overall about 30% are malignant
      • Usually adenocarcinoma in mature teratomas
      • Angiosarcoma or rhabdomyosarcoma in immature teratomas
  • Most of the cystic lesions are benign and most of the solid lesions are malignant
  • Both occur early in life—young adults most commonly
    • DDX from thymomas which usually occur in 5th or 6th decade
  • Symptoms
    • Usually asymptomatic
    • Large lesions can cause shortness of breath, cough or retrosternal pain or fullness
    • Rare rupture of dermoid into trachea which leads to trichoptysis—expectoration of hair
  • Associations
    • Non-lymphocytic leukemia and malignant histiocytosis with immature teratomas
  • Imaging findings
    • Most occur in the anterior mediastinum, near junction of great vessels and heart
    • Benign lesions are usually smooth in contour whereas malignant masses tend to be lobulated
    • Usually larger than thymomas
    • Calcification may rarely occur but is of no help since thymomas also calcify
      • Exception would be the very rare occurrence of a tooth or bone in a dermoid
    • CT shows fatty mass with globular calcifications and rarely a tooth or bone
      • Fat-fluid level may be seen on CT

Enhanced CT scan of the chest shows large, septated anterior
mediastinal mass containing fat and bony elements

  • Rapid increase in size may mean hemorrhage into a cyst rather than enlarging malignancy
  • Treatment and prognosis
    • Mature teratomas
      • For benign cystic teratomas, surgical resection
      • Excellent prognosis
    • Immature teratomas
      • In childhood, surgical excision is often successful
      • In adults, tend to have a more malignant course
    • Teratomas with malignancy
      • Usually highly aggressive
      • Poor prognosis
  • Teratoma versus dermoid
    • Dermoid contain only epidermis
    • Teratomas contain all 3 germ layers, but are mostly endodermal when malignant
  • Other germ cell neoplasms
    • Benign dermoid cysts
    • Benign and malignant teratomas
    • Seminomas
    • Choriocarcinomas
    • Embryonal cell carcinomas
  • Mediastinal seminomas
    • Rare
    • Almost always in young men
    • Identical to testicular seminoma and ovarian dysgerminoma
    • May be well-encapsulated or invasive
    • Tends to be lobulated
    • Cannot be differentiated from teratoma
  • Primary choriocarcinoma
    • Even rarer than seminoma in the mediastinum
    • Only 23 reported in the literature, almost all in men
    • Occur between 20-30 years
    • May be lobulated
    • May have elevated beta sub unit of HCG
    • Growth is very rapid leading to dyspnea, hemoptysis, stridor
    • Gynecomastia and a + Aschheim-Zondek test can occur
    • Rapidly fatal

  Mediastinal Teratoma

Mediastinal Teratoma. Contrast-enhanced axial CT scan of the chest demonstrates an anterior mediastinal mass containing calcification (black arrow), fat (white arrow) and soft tissue components (dotted white arrow).
For this same photo without the arrows, click here
For more information, click on the link if you see this icon

Fraser and Pare