Adrenal incidentaloma: an adrenal lump found by chance on a scan

The adrenal glands are two small glands that sit above the kidneys and make hormones including cortisol, aldosterone and adrenaline-like substances. An incidentaloma is simply a lump found by accident, for example on a CT scan of the abdomen requested for abdominal pain or after an injury. The NHS guideline from North Bristol NHS Trust describes the term as covering lesions found on diagnostic imaging without prior clinical suspicion of tumour or disease.

The label covers a range of things. The guideline lists endocrinologically inactive lesions such as adenomas, myelolipomas, cysts and haemorrhage, as well as rarer lesions such as carcinoma and metastasis, and endocrinologically active lesions such as phaeochromocytoma and cortisol- or aldosterone-producing tumours. The purpose of the assessment is to sort the lump into one of these groups.

Imaging use has increased greatly in recent decades, so these lumps are found more often. The North Bristol guideline says prevalence increases with age, being very rare in childhood, rising to around 3 per cent at age 50 and around 10 per cent in the elderly. The Endocrine Reviews article, authored by clinicians in Dublin and Leeds, reports that about 2 per cent of people with an adrenal incidentaloma have adrenocortical cancer, and up to 10 per cent have autonomous secretion of adrenal hormones.

Both sources emphasise reassurance as the usual outcome. The guideline says that where the baseline assessment confirms a benign and hormonally inactive lesion, the risk of malignant transformation is 0.2 per cent and the risk of developing overt hormone excess is at most around 2 per cent, so a pragmatic approach to follow-up is warranted.

By definition the lump itself is found without symptoms. Where symptoms exist, they are those of the hormone being produced in excess. The guideline's comorbidity list for cortisol excess includes hypertension, type 2 diabetes, obesity, dyslipidaemia, impaired glucose tolerance and osteoporosis. The guideline recommends testing for aldosterone excess only in people who also have high blood pressure or unexplained low potassium.

If a scan report mentions an adrenal lesion, ask your GP who will follow it up. The guideline's advice is for medical staff who identify a possible adrenal incidentaloma to refer promptly to an endocrine team, and the very young, adolescents, pregnant women and adults under 40 are assessed urgently because of a higher likelihood of malignancy.

The assessment has two parts: imaging to characterise the lump, and hormone tests to see whether it is active. The guideline describes the following approach for lesions over 1 cm, since those under 1 cm usually do not need further investigation unless symptoms dictate.

The Endocrine Reviews article explains that size matters: it quotes a 2 per cent risk of adrenocortical cancer in lesions under 4 cm, 6 per cent in those 4.1 to 6 cm and 25 per cent above 6 cm, and notes that European guidelines recommend no further imaging for lesions with benign characteristics under 4 cm. For people with a past history of cancer elsewhere, an indeterminate lesion may call for further imaging such as PET-CT, because the adrenal can be a site of spread.

Most people need no treatment. The review says most patients can be discharged once malignancy and hormone hypersecretion have been excluded. Surgery, usually removal of the affected adrenal gland, is considered where tests suggest malignancy or significant hormone excess; the review says any indeterminate nodule greater than 4 cm should be offered surgery, and that surgery may be considered in larger lesions even if the imaging looks benign.

The decision is more nuanced for mild autonomous cortisol secretion. The North Bristol guideline notes that the risk of progression to overt Cushing's syndrome is very low, at less than 1 per cent, but that the condition may be associated with cortisol-related comorbidities, so blood pressure, glucose, lipids and bone density are checked, and surgery can be offered to individually counselled patients who have relevant comorbidities. The Endocrine Reviews article cautions that a causal link between cortisol hypersecretion and age-related comorbidities should be firmly established before recommending surgery.

On the NHS the usual route is referral from the clinician who requested the scan, or from your GP, to an endocrinology service, sometimes with discussion at a multidisciplinary meeting for complex cases. The hormone tests are routine blood and urine tests and an overnight tablet test.

A private endocrinologist can arrange the same tests more quickly. The decisions are the same either way, so it is worth asking for the original scan report and images to be shared so that tests are not repeated, and clarifying who will arrange any follow-up imaging.