Microsomal Aromatase in Testicular Tumour Tissue: Increased Activity in Choriocarcinoma Compared to Embryonal Carcinoma

Summary Microsomal aromatase activity was assayed in testicular tumour tissue from one patient with Choriocarcinoma and two patients with embryonal carcinoma. In the microsomal fractions of tumour tissue conversion of 3 H-testosterone and 3 H-androstenedione to 3 H-17β-estradiol and 3 H-estrone was measured. Aromatase activity was markedly increased (8-fold) in Choriocarcinoma compared to embryonal carcinoma. In the Choriocarcinoma patient, high HCG-levels measured in serum and the increased aromatase activity in the tumour with resulting elevated estrogen levels in serum seem to be responsible for the decreased production of androgen in this type of tumour.