ADRENALS

Question 1

INCIDENTAL ADRENAL
MASS (UNILATERAL)
Functioning tumours

Answer 1

1. Conn’s adenoma—accounts for 70% of Conn’s syndrome. Usually
   small, homogeneous, relatively low density due to cholesterol
   content. 30% of Conn’s syndrome is due to bilateral hyperplasia,
   which can occasionally be nodular and mimic an adenoma. Note
   that functioning and nonfunctioning adenomas are essentially
   indistinguishable on imaging, although functioning adenomas tend
   to be smaller and are more likely to be lipid-rich.
2. Phaeochromocytoma—usually large (>5 cm) with avid contrast
   enhancement ± central necrosis/haemorrhage (NB: it is safe to
   administer IV iodinated CT contrast). Often markedly T2
   hyperintense on MRI. Rule of tens: 10% malignant, 10% bilateral,
   10% ectopic—of these 50% are located around the kidney,
   particularly the renal hilum (if not seen on CT, MIBG isotope scan
   may be helpful). 10% show calcification. 10% are multiple and
   usually part of MEN 2A/B syndrome, NF1, tuberous sclerosis or
   vHL.
3. Cushing’s adenoma—accounts for 10% of Cushing’s syndrome.
   Usually >2 cm. 80% of Cushing’s syndrome is due to excess ACTH
   from a pituitary adenoma (Cushing’s disease) or ectopic source
   (small cell carcinoma, carcinoid, pancreatic NET,
   phaeochromocytoma, medullary thyroid carcinoma) with resultant
   adrenal hyperplasia. 10% of Cushing’s syndrome is due to adrenal
   carcinoma. The differentials for an adrenal mass in Cushing’s
   syndrome are:
   (a) Functioning adenoma/carcinoma—atrophy of the contralateral
   adrenal is suggestive.
   (b) Coincidental nonfunctioning adenoma—both adrenals may be
   hyperplastic (due to excess ACTH).
   (c) Metastasis from small cell primary.
   (d) Bilateral nodular hyperplasia—see Section 9.2.
4. Adrenal carcinoma—rare, usually large (>5 cm). Functioning
   tumours (<50%) may present with Cushing’s, virilization,
   feminization or rarely Conn’s, and are more common in
   women

Question 2

INCIDENTAL ADRENAL
MASS (UNILATERAL)
Malignant tumours

Answer 2

. Metastases—often bilateral, usually >2 cm, irregular outline with
patchy contrast enhancement. Common sources include lung,
breast, renal and GI tract. Metastases from melanoma and RCC are
usually hypervascular and may mimic phaeochromocytoma. Recent
haemorrhage into a vascular metastasis can produce patchy high Adrenals, urinary tract, testes and prostate 229
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attenuation on unenhanced CT. In patients without a known
extraadrenal primary tumour, the vast majority of adrenal masses
are benign; in the presence of a known primary malignancy
26-36% of adrenal lesions are metastatic.
2. Carcinoma—rare, aggressive. Typically a large (>5 cm), irregular,
heterogeneously enhancing mass with central necrosis/
haemorrhage ± foci of calcification and nodal, metastatic and/or
intravenous spread. May invade the adjacent kidney, making it
difficult to distinguish from an advanced RCC. Nonfunctioning
tumours (>50%) are more common in men and present at a larger
size than functioning tumours.
3. Lymphoma*—usually secondary in the presence of retroperitoneal
nodal disease. Unilateral or bilateral adrenal masses/diffuse
enlargement + mild homogeneous enhancement.
4. Neuroblastoma—very rare in adults. Usually large (>5 cm),
ill-defined and heterogeneous + calcification. Commonly surrounds
and displaces vessels (e.g. aorta and IVC) without causing
significant narrowing. Metastases are common at presentation.
5. Sarcoma—e.g. angiosarcoma, leiomyosarcoma. Very rare.
Nonspecific appearances: aggressive, irregular, heterogeneously
enhancing mass.

Question 3

INCIDENTAL ADRENAL
MASS (UNILATERAL)
Benign
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Answer 3

1. Nonfunctioning adenoma—very common. Usually small (50%
   <2 cm), homogeneous and well-defined. If lipid-rich, will have
   unenhanced CT attenuation <10 HU and will drop signal on
   out-of-phase T1-weighted MRI.
2. Myelolipoma—benign tumour composed of fat and haemopoietic
   tissue. Characteristic appearance on CT: discrete mass containing
   soft tissue and macroscopic fat (L), but can also occur in vascular
   masses (e.g. phaeochromocytoma, metastases), coagulopathies
   and severe stress (e.g. surgery, sepsis, burns, pregnancy,
   hypotension—often bilateral).
3. Cyst—round, well-defined, water density, nonenhancing. May
   contain thin septa ± mural calcification. Pseudocysts due to
   previous haemorrhage > true cysts. Beware of cystic tumours (e.g.
   some phaeochromocytomas)—look for nodular wall thickening. If
   multiloculated, consider lymphangioma and hydatid cyst in the
   differential.
4. Granulomatous disease—e.g. TB, histoplasmosis. More commonly
   bilateral, see Section 9.2.
5. Haemangioma—rare. Often contains phleboliths. Typically
   demonstrates peripheral nodular enhancement ± partial infilling on
   delayed phase. Central fibrotic scar usually does not enhance.
   Peripheral nonfibrotic component is usually markedly T2
   hyperintense. May mimic phaeochromocytoma.
6. Ganglioneuroma—rare, occurs in children or young adults.
   Benign counterpart of neuroblastoma, arises from sympathetic
   ganglia. Well-defined, often shows heterogeneous delayed
   enhancement. Heterogeneously T2 hyperintense on MRI ± whorled
   appearance. Calcification is common.
7. Other very rare lesions—adrenal lipoma, teratoma and
   angiomyolipoma can mimic myelolipoma due to macroscopic fat
   content (a fat–fluid level suggests teratoma). Schwannomas may
   be cystic ± calcification. Solitary fibrous tumours, leiomyomas,
   oncocytomas and inflammatory pseudotumours have also been
   rarely reported in the adrenals
   and present as a nonspecific solid heterogeneously enhancing
   mass.
8. Pseudolesions—e.g. exophytic renal/hepatic/pancreatic mass,
   gastric diverticulum, splenunculus, retroperitoneal varices. These
   can occasionally mimic an adrenal mass but IV/oral contrast and
   coronal reconstructions will nearly always clarify the diagnosis

Question 4

BILATERAL ADRENAL MASSES

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Answer 4

1. Metastases—bilateral in 15%. Usually do not affect adrenal
   function; may cause adrenal insufficiency if extensive (replacing
   >80% of adrenal gland).
2. Phaeochromocytoma—bilateral in 10%. Suggests an underlying
   hereditary cause, e.g. MEN 2A/B, NF1, tuberous sclerosis or vHL.
3. Adenomas—due to the prevalence of adenomas, they can
   occasionally be bilateral.
4. Hyperplasia—congenital adrenal hyperplasia results in
   symmetrically enlarged and thickened adrenal glands in children.
   In adults, adrenal hyperplasia has several causes:
   (a) ACTH-dependent hyperplasia—more commonly due to ectopic
   ACTH secretion, but can occur in Cushing’s disease. Adrenals
   are usually mildly and diffusely enlarged but may be nodular
   in morphology.
   (b) ACTH-independent macronodular adrenocortical hyperplasia
   (AIMAH)—rare. Multiple bilateral large adrenal adenomas,
   each typically >1 cm and lipid-rich.
   (c) Primary pigmented nodular adrenocortical disease (PPNAD)—
   rare, autosomal dominant, typically presents in young females.
   Multiple bilateral adrenal micronodules, each usually <5 mm.
   Strongly associated with Carney complex.
5. Adrenal haemorrhage—often bilateral in cases due to severe
   haemodynamic stress.
6. Granulomatous disease—histoplasmosis/TB. Bilateral adrenal
   masses/enlargement ± central necrosis ± adrenal insufficiency in
   the acute setting. Results in adrenal atrophy and calcification in the
   chronic setting.
7. Lymphoma*—primary adrenal lymphoma is rare; typically presents
   with bilateral large homogeneous adrenal masses/diffuse
   enlargement, often with adrenal insufficiency. Secondary adrenal
   involvement is more common, usually without adrenal
   insufficiency.

Question 5

ADRENAL CALCIFICATION

Answer 5

1. Previous haemorrhage—unilateral or bilateral depending on
   aetiology. Old haemorrhage within a mass lesion (e.g. a large
   adenoma, myelolipoma or hypervascular metastasis) can also lead
   to calcification.232 Aids to Radiological Differential Diagnosis
2. Cystic disease—curvilinear calcification within the cyst wall/septa.
   More common in pseudocysts than true cysts. Can also be seen in
   chronic hydatid cysts.
3. Chronic TB*/histoplasmosis—atrophic calcified adrenals (often
   bilateral).
4. Calcification within a tumour—e.g. adrenal carcinoma (irregular
   punctate calcifications in 30%), phaeochromocytoma (10%),
   neuroblastoma (up to 90%, coarse/amorphous pattern),
   ganglioneuroma (fine/speckled pattern), haemangioma
   (phleboliths), teratoma and certain metastases (e.g. from mucinous
   adenocarcinoma, osteosarcoma).
5. Addison’s disease—calcification is rare in primary autoimmune
   disease, and suggests a secondary cause, e.g. previous
   haemorrhage, TB or histoplasmosis.
6. Wolman disease—rare autosomal recessive lysosomal acid lipase
   deficiency resulting in accumulation of cholesterol and triglycerides
   in organs. Presents in early infancy with failure to thrive.
   Pathognomonic appearance of enlarged densely calcified adrenals
   on AXR, US or CT. Fatty infiltration and enlargement of the liver,
   spleen and lymph nodes also occurs