Adrenal nodules

The most common reason an adrenal nodule is found is as an incidental finding during an imaging test for something else. Spots are frequently seen on the adrenal gland and are called "adrenal incidentalomas". An adrenal incidentaloma is usually greater than 1 centimeter in size and serendipitously discovered by radiologists during an exam such as CT or MRI. The rate of finding such growths is 4 to 10%, higher with age. 

There are basically two main questions about these growths
1. Is it malignant?
2. Is is functioning?

Is it cancer?
The likelihood of cancer is quite low if a cancer diagnosis is not already known. The chances of cancer are best evaluated by a urologist and radiologist by use of imaging characteristics. An imaging test can help decide if the mass is mostly fatty or mostly solid / non-fatty. Fatty growths on the adrenal gland are almost always benign.  Non-fatty growth may or may not be benign and will need further imaging or invasive follow up by a urologist or endocrine surgeon. 
For example, on dedicated adrenal CT scanning the density of the image is rated by "Housfield units" which is a semi-quantitative way to measure "fattiness". Baseline pre-IV contrast values of fatty tissue are negative 20 to negative 150 Housfield units (HU). If an adrenal mass measures less than 10 HU on non-contrast CT then the likelihood of benign mass is 100% and is called an "adrenal adenoma" But 30% of adenomas do not contain large amounts of fat tissue and then a CT with timed IV contrast can give additional information. Ten minutes after administration of the contrast, an absolute contrast medium washout of more than 50% was reported to be 100% sensitive and specific for a benign adrenal adenoma. Otherwise surgery should be considered. Also MRI and PET scanning has their own sets of benign features.

The maximum size of an adrenal mass is predict of cancer. 90 % of adrencal carcinomas are more than 4cm when discovered. Therefore surgery should strongly be considered for any >4cm tumors discovered, especially in younger patients. 

Is it hormonally active?
There are 4 major hormones secreted by the adrenal gland: metanephrines (adrenaline), cortisol, DHEA, and aldosterone. Both benign and malignant adrenal nodules can potentially over-secrete these hormones. An endocrinologist can easily determine if these hormones are being secreted in excess.  Ten to 15% of adrenal incidentalomas secreate too much hormone. Subclinical cushings (excess cortisol) and pheochromocytoma are sufficienctly common that ALL patients with an adrenal incidentaloma should be tested for these disorders. If a patient has hypertension then aldosterone testing should be done as well. 

1. Adrenal incidentaloma: an overview of clinical and epidemiological data from the National Italian Study Group.  Angeli A et al
Clinical utility of noncontrast computed tomography attenuation value (housfield units) to differentiate adrenal adenomas/hyperplasias from nonadenomas. Cleveland Clinic Experience.  Hamrahian et al.