Angiotensin I-converting enzyme in a suprasellar germinoma.

High levels of angiotensin I-converting enzyme (ACE) were found by both direct radioimmunoassay and enzyme activity evaluation in a patient's plasma that had suprasellar germinoma. ACE levels returned to normal values after surgery, suggesting the tumor was the cause of the elevated plasma ACE. ACE was found in the tumor, and ACE activity was measured in a tumor extract. With the use of specific antihuman ACE antibodies, ACE was localized by immunohistochemistry in the tumoral germinal cells. Because ACE was also found in testicular germinomas, it appears to be a possible marker for germ cell tumors.