Neurogenic tumours

urinary catecholamines. When those results are positive then imaging is performed to try and localise the tumour.

Adrenal

They most frequently arises from the chromaffin cells of the adrenal medulla.

Extra adrenal locations

Approximately 10% of all pheochromocytomas are not located in the adrenal glands. Extraadrenal tumours are more likely to be malignant and metastasise 4.

They can be found along the sympathetic chain as well as in the urinary bladder and organ of Zuckerkandl. Thoracic paragangliomas are rare and only account for 1 - 2 % of all cases of pheochromocytoma.

Radiographic features

As a general rule tumours in the adrenal region tend to be large at presentation, usually larger than 3 cm, with an average size of ≈ 5 cm. When confined to the adrenal glands, and especially if suspected clinically the diagnosis is readily made. Small extra-adrenal tumours can however be a challenge to find. Overall 98% of tumours are in the abdomen, and 90% are confined to the adrenal glands 6.

It is also important to note that it is not possible to distinguish malignant from benign pheochromocytomas merely on the direct appearance of the mass. Rather, the distinction is made on demonstrating evidence of direct tumour invasion into adjacent organs / structures or the presence of metastases 4.

CT

CT is the first imaging modality to be used, with an overall sensitivity of 89%. This is on account of 98% of tumours being located within the abdomen and 90% limited to the adrenal glands 6.

On CT pheochromocytomas are large usually heterogeneous masses with areas of necrosis and cystic change.

approximately 81% 6.

PET

18F Dopa PET is thought to be highly sensitive according to initial results 3

Treatment and prognosis

Definitive treatment is surgical, and if complete resection is achieved, without metastases, then surgery is curative, and hypertension usually resolves.

Pre-operative medical management is essential in reducing the risk of intra-operative hypertensive crises and typically consists of non-competitive alpha adrenergic blockade (e.g. phenoxybenzamine). Later (but never before 7-10 days of alpha blockade) a beta blocker may need to be added to control tachycardia or some arrhythmias 5-6.

Metastases from malignant pheochromocytomas are typically to lung, bone and liver 4.

Differential diagnosis

When located in the adrenal gland, the

differential is essentially that of an adrenal tumour, and includes :

•adrenal adenoma

•adrenal carcinoma

•adrenal metastasis(es)

In large tumours, especially if malignant, differentiating them from renal cell carcinomas can be difficult, especially on CT.

Adrenal cortical carcinoma

A primary adrenal cortical carcinoma is a highly malignant but rare neoplasm. It may present as a hormonally active or inactive tumour.

Epidemiology

Although men and women are affected equally, functioning tumours are more common in females, who are also more likely to have an associated endocrine syndrome 5. Median age of presentation is ~ 50 years, but tumours have been found at all ages 3,4.

An additional, but smaller, incidence peak occurs in early childhood. In these cases tumours are more likely to be functioning 5.

Incidence is low, ranging from 0.6 to 1.67 per million, per year 5.

Clinical presentation

Hormonally inactive tumours present as palpable masses, abdominal pain or with evidence of metastasis. Hormonally active tumours, representing 30 - 40% of all adult

tumours, present with characteristic clinical manifestations 3-5.

14.Cushing syndrome secondary to elevated cortisol

15.virilization or feminization secondary to elevated androgens

16.Conn syndrome secondary to

hyperaldosteronism (rare)

Associations

• Beckwith Wiedemann syndrome

Radiographic features

Ultrasound

Often a suprarenal well defined mass is seen, the appearance of which varies based on size of lesion. Smaller lesions are homogenous, whereas larger lesions are heterogenous secondary to necrosis/haemorrhage.

CT

CT is usually the first imaging modality used. Adrenal carcinomas tend to be large (> 6 cm) irregular shaped mass with central areas of necrosis and haemorrhage, resulting in variable enhancement. Calcification is seen in upto 30%

of cases.

If the mass is found early, when still small, then it is difficult to distinguish from an adenoma, as aggressive features are often absent 5.

Focal extension into renal vein, IVC and liver are relatively common, with some series finding renal vein involvement in up to 40% of patients 5. Metastasis to regional lymph nodes and lung can occur.

MRI

MRI can be useful to determine hepatic invasion if CT is inconclusive.

Heterogeneous mass is seen that is of high

the haemorrhage. Heterogeneous enhancement is seen with administration of gadolinium.1,4

Angiography

Arteriography is performed in patients who present with a large mass for which the organ of origin cannot be determined. 3 Selective catherisation can identify the primary vascular

supply, and thus help distinguish adrenal from renal tumours.

Treatment and prognosis

Ideally treatment is with surgical excision, however in many instances disease is advanced at the time of diagnosis, in which case chemotherapy (Mitotane) and radiation may be given for palliation.

In general males have a poorer prognosis, largely because they are less likely to have functioning tumours, and thus present later, with more advanced disease 5.

Differential diagnosis

For an adrenal mass consider other adrenal lesions 2, such as:

•adrenal metastases

•adrenal adenoma

•adrenal haemorrhage

•phaeochromocytoma

will look identical on imaging differentiation is on histology and

biochemistry / functional status