Adrenal Tumors: Diagnosis

2023 Author: Wallace Forman | [email protected]. Last modified: 2023-05-24 12:25

Adrenal tumors: diagnosis

Every adrenal tumor needs further laboratory tests, even if it is an incidental finding. The determination of the adrenal cortex and medullary hormones is an essential part of the diagnosis. It is important to distinguish whether the tumor leads to increased hormone production (is hormone-active) or whether it does not produce hormones (hormone-inactive). It is particularly important to safely exclude a pheochromocytoma, which can release stress hormones continuously or in spurts.

In addition, special imaging examinations (sectional image examinations such as CT or MRT) are carried out to assess the size and extent of the tumor (e.g. ingrowth into neighboring organs and vessels). The doctor receives the first important information as to whether the tumor is benign or malignant.

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How is the diagnosis made?

Hormone-active tumors of the adrenal cortex lead to different clinical symptoms. The first diagnostic step consists of a detailed anamnesis and a physical examination. If a hormonal disorder is suspected, the next step is a so-called endocrine functional diagnosis. This means that special tests are carried out to detect changes in hormone production.

More on the topic: Adrenal Tumors Forms & Symptoms

Endocrine function diagnostics: determination of the adrenal hormone levels

• If an excess of the stress hormones adrenaline and noradrenaline is suspected, an examination of the acidified 24-hour urine and blood plasma is carried out; the degradation products (metanephrines) are detected in it. Reproducibly increased hormone levels are evidence of a pheochromocytoma. If the results are unclear, further tests, such as the clonidine test, are carried out. Clonidine is a drug that centrally suppresses the release of adrenaline and noradrenaline. If the hormone levels remain elevated after taking clonidine, this makes a pheochromocytoma likely.
• If aldosterone overproduction is suspected, the aldosterone concentration is determined in relation to the concentration of the hormone renin (these two hormones work closely together in the salt and water balance). Determining aldosterone alone is not very meaningful because its concentration is influenced by many factors and changes frequently. The so-called renin-aldosterone quotient allows conclusions to be drawn about the function of the adrenal cortex. If the result is conspicuous, a saline test can confirm the suspicion: It checks whether the aldosterone level in the blood drops after the supply of a saline solution, as it should be physiological. If this is not the case, aldosterone overproduction (Conn syndrome) can be assumed.
• If an excess of cortisol is suspected, the cortisol level in the blood is determined in the 24-hour urine collection (or in the saliva). The dexamethasone test is an important part of confirming hormone overproduction. Dexamethasone is a drug that suppresses cortisol production. If the cortisol level in the blood remains high despite taking dexamethasone, this indicates an overproduction of cortisol (hypercortisolism). In a further step, it is determined whether the cause of the hormone overproduction is a tumor of the adrenal gland (Cushing's syndrome) or a tumor of the pituitary gland (pituitary gland). A CRH test is carried out to differentiate: CRH is a hormone of the diencephalon (hypothalamus),which in a physiological control loop ultimately leads to an increase in cortisol production in the adrenal gland. If the cortisol level in the blood does not rise in spite of the administration of CRH, this indicates a tumor of the adrenal gland.

Imaging examinations

If an overproduction of adrenal hormones has been confirmed, the next step is a cross-sectional examination (computed tomography or magnetic resonance tomography) with administration of contrast medium. The size of the tumor, its exact localization and delimitation (tumor capsule), the tissue density (homogeneity, ie whether the node is evenly structured) and its behavior to surrounding structures can be displayed.

Using certain criteria, CT (or better still, MRT) can reliably estimate whether the tumor could be benign or malignant. The tissue density (by attenuating X-rays) can be represented in so-called Houndsfield units (HU) on the Houndsfield scale. This allows conclusions to be drawn about the type of tissue (more malignant or more benign): Benign adrenal tumors (adenomas) have low HUs (less than ten HU). Houndsfield units of ten or more are suspected of malignancy, further diagnostic steps are necessary, such as functional examination with positron emission tomography (PET-CT).

The tumor size can also provide an important indication of whether the tumor is benign or malignant: the greater the tumor size, the greater the likelihood of a malignant tumor (adrenal carcinoma). Adrenal tumors less than four centimeters in diameter are malignant in only two percent of cases. By contrast, tumors with a diameter of more than six centimeters are malignant in over 25 percent.

Note In contrast to many other tumor diseases, no fine needle biopsy is carried out for further diagnosis of adrenal gland tumors, as it does not allow a clear distinction between benign and malignant tumors. If the pheochromocytoma is undetected, a biopsy can be life-threatening. A biopsy can lead to an excessive release of adrenaline and noradrenaline and thus to severe blood pressure crises with cerebral haemorrhage.

A fine needle biopsy is only performed in individual cases when a pheochromocytoma can be safely ruled out and there is a suspicion of metastases from other malignant tumors remote from the adrenal gland (e.g. lung cancer).

Further investigation procedures

Depending on the diagnosis, additional procedures can be used for further clarification. For example, after the diagnosis of a pheochromocytoma, nuclear medical examinations such as I-MIBG scintigraphy or F-DOPA-PET-CT are carried out. MIBG (meta-iodo-benzylguanidine) is a weakly radioactive substance that is chemically related to noradrenaline and adrenaline. After administration, it is therefore mainly stored in cells that produce these hormones - ie in pheochromocytomas. These enrichments can be visualized using scintigraphy. The primary purpose of the examination is to detect tumor cells that are located outside the adrenal gland (extraadrenal pheochromocytoma or metastases). The so-called F-DOPA-PET-CT examination also uses the property of tumor cells,absorb certain substances. This includes radioactively labeled DOPA, which is administered as part of this examination. Even small tumors or distant metastases of malignant pheochromocytomas can be made visible through the increased enrichment and thus localized.

What is the procedure for a symptom-free, accidentally discovered tumor?

Adrenal tumors that do not cause symptoms are often described by chance during imaging tests that were actually performed for other reasons. One then speaks of an incidentaloma. In 80 percent of cases, these are hormone-inactive, benign tumors (adenomas). However, it can also be caused by hormone-producing tumors (e.g. small pheochromocytomas) as well as adrenal carcinomas (in two to five percent of cases) or metastases (in around one to 2.5 percent of cases). Further clarification is therefore essential.

This includes, on the one hand, a laboratory test with endocrinological function diagnostics, because a possible (mild) hormone overproduction must always be reliably excluded. As a rule, a dexamethasone test and the determination of norepinephrine and adrenaline breakdown products in the blood (plasma metanephrine; plasma normetanphrine) and the excretion of adrenaline, noradrenaline, dopamine and the building products metanephrine, normetanephrine in the acidified 24-hour test Collective urine carried out. In addition, the aldosterone-renin quotient is determined. Depending on the result, further tests may be necessary (see above).

In addition, various radiological examinations must be used to assess whether the tumor is benign or malignant. If this is not possible based on the first (accidental) finding, further imaging examinations are carried out.