Aromatase expression in human germinomas with possible biological effects.

Gonadal aromatase expression has been demonstrated in human Leydig, granulosa, and thecal cells, but never in human germ cells. In an attempt to explain the unique occurrence of isosexual precocious puberty in a young girl with a hCG-secreting suprasellar germinoma, we demonstrated the presence of aromatase expression in the germ cell component of this tumor. Immunohistochemical staining for P450-aromatase and hCG using a peroxidase-labeled streptaviden-biotin technique was performed on tumor specimens from the above patient and from four other subjects with central nervous system germinoma. Cytoplasmic aromatase staining was present in the germinoma cells of four of five cases of central nervous system germinoma studied. Staining was absent in the lymphocytic element within the tumor and in negative control tissues. The demonstration of aromatase activity in the malignant element of human germinomas indicates that aromatase expression can occur in human germ cells after malignant transformation. This parallels the finding that the transformation of Sertoli cells to sex cord tumor with annular tubules in Peutz Jeghers syndrome is associated with the induction of marked aromatase expression and systemic estrogen effect. We propose that tumor aromatase played a similar role in the unique occurrence of isosexual precocity in a girl with a suprasellar germinoma.