Four to 6% of adult patients have an adrenal mass. These tumors are found, incidentally, on CT scans or MRI done to evaluate unrelated signs and symptoms. Adrenal tumors found in this way are known as incidentalomas.
When an adrenal mass is discovered unexpectedly, two questions must be answered:
- Is it cancer?
- Is it functioning?
Incidentalomas are rarely malignant. The best way to judge this is through careful imaging with either a CT scan or MRI. A tumor < 4 cm has only a 2% chance of being malignant. A tumor over 6 cm has a 25% chance of malignancy. The amount of fat in the tumor (which can be estimated by CT scan or MRI) as well how rapidly contrast washes out of the tumor is predictive of malignancy. A biopsy is generally not indicated because it is difficult for the pathologist to diagnose cancer on biopsy only and because the risk of spreading the tumor cells, if it is cancer, is significant. Small tumors, without worrisome features are rarely malignant and can be safely observed.
Determining the functional status of the tumor is done by performing screening test for Cushing syndrome, pheochromocytoma, Conn’s syndrome or examining for evidence of excess sex steroid secretion. If these tests are negative observation may be appropriate.
If the answer to the either question is “yes” then surgical removal is indicated. Most commonly we recommend a laparoscopic adrenalectomy. If the answer to both questions is “no” then observation is indicated. Usually we recommend a CT scan every 6 months for 1-2 years, then yearly after that. As long as no worrisome feature develop, the incidentaloma may be observed indefinitely.