Learning Radiology xray montage
 
 
 
 
 

Mediastinal Teratoma
Dermoid

  • 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

  • Clinical Findings

    • 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

Mediastinal Teratoma

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

 

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