Elevated right hemidiaphragm

Clinical History

A 32-year-old woman, without any known significant clinical problems, was admitted to the emergency department with a cough and fever. Chest x-ray was performed to rule out pneumonia.

Imaging Findings

Chest-x ray showed a slight right hemidiaphragm elevation (abnormal when the right hemidiaphgram is more than 3 cm higher than the left) (Fig. 1).
At physical examination, a right hypochondrial mass was then palpated.
Ultrasound showed a solid sub-hepatic mass (Fig. 2).
At CT a large mass was noted, centred on the right adrenal gland, displacing the liver upwards. It showed several central calcifications, and was relatively hypovascular to the liver on venous-phase (Fig. 3).
At MRI, the mass was heterogeneous on T2 and T1, as a reflection of cystic, necrotic and haemorrhagic changes. On in and out-of-phase GRE images there was no evidence of microscopic fat. The contrast uptake dynamics were similar to the already noted on the CT, showing a markedly hypovascular mass. Peripheral restriction to diffusion could also be appreciated (Fig. 4).
The lesion was surgically resected and diagnosed as primary adrenocortical carcinoma (Fig. 5).

Discussion

Adrenocortical carcinoma (ACC) is a rare highly malignant tumour with a poor prognosis and a yearly incidence of 1/1.000.000. It may be hormonally active, presenting with Cushing or Conn syndrome. When hormonally inactive, it commonly presents as a palpable mass, abdominal pain or metastatic disease [1, 2].

CT usually shows a large heterogeneous mass, due to internal haemorrhage and necrosis. Up to 30% have foci of calcification. It tends to displace the adjacent structures and invasion of the adrenal veins and inferior vena cava is not uncommon. Regional lymphadenopathy and metastases are common [3].
MRI is valuable in the evaluation of ACC, as it allows better assessment of invasion of adjacent structures. Both T2W and T1W images show an inhomogeneous mass due to necrosis and haemorrhage. There may be areas of intracellular lipid which result in a loss of signal on out-phase images. The contrast enhancement is commonly intense and heterogeneous with slow washout.

The differential diagnosis of an adrenal lesion is broad:
Adrenal adenomas and metastases are the most common cause of adrenal lesions. Metastases should be considered when adrenal lesions are bilateral, there is evidence of other metastases or there is a known primary malignancy.
Adrenal adenomas are usually small, homogenous, and have a low density (< 10 HU) due to high intracellular lipid content. Nonetheless, when bigger, distinction between ACC may be difficult as adenomas may present as heterogeneous masses with necrotic and haemorrhagic changes and central calcifications. In these cases, the rate of growth has to be taken into account and the only definite criteria for malignancy is the presence of metastatic disease.
The presence of macroscopic fat in an adrenal mass has classically been associated with myelolipoma, however, several cases of ACC containing macroscopic fat have been described [4].
Adrenal haemorrhage may be suspected if there is history of trauma; anticoagulation of bleeding diatheses. Acute to subacute haematomas contain areas of high attenuation that usually range from 50-90HU.
Pheochromocytoma is also a rare tumour, usually measuring between 3-5 cm. Classically described as having central cystic changes, may however have extensive imaging features. Biochemical measurement of plasmatic metanephrines and 24-hour urinary catecholamines should be the first step in the diagnostic workup.

Finally, even though primary adrenocortical carcinoma is a rare diagnosis, it is important to keep it in mind. It is an aggressive tumour, with a median survival of only 6 months if left untreated, and potentially surgically curable if detected early [3].

Differential Diagnosis List

Final Diagnosis

Primary Adrenocortical Carcinoma

URL:	https://eurorad.org/case/13933
DOI:	10.1594/EURORAD/CASE.13933
ISSN:	1563-4086