Leydig Cell Tumors

• Facts:
  -MC testicular sex cord stromal tumor
  
  -Leydig cells are principal source of testosterone, but are also capable of estrogen production, due to markedly increased aromatase activity
  
  -Increased estrogen, causes secondary inhibition of LH/FSH
  
• History / PE:
  -Gynecomastia
  -Precocious puberty
• Diagnosis:
  Increased testosterone and estradiol
• Differential Diagnosis:
  Choriocarcinoma (increased beta-HCG)
  Yolk sac tumor (endodermal sinus tumor, increase AFP)