A rare adrenocortical tumour: myxoid adrenal carcinoma

Clinical History

Male patient, 54 years old. During an abdominal ultrasound examination an enlargement of the right adrenal gland was incidentally detected. Due to these findings, specific studies, such as computed tomography (CT) and magnetic resonance imaging (MRI), were carried out. The patient had no symptoms and laboratory tests were within normal ranges.

Imaging Findings

The abdominal ultrasound revealed a rounded soft tissue echogenicity image in the right adrenal area, reaching up to 3 cm in diameter.

A non-contrast CT confirmed a well-defined ovoid-shaped nodule in the right adrenal gland. It presented attenuation values ranging from 10 to 25 Hounsfield Units (HU) (Fig. 1).

On MR, the lesion was hyperintense on T2-weighted images (Fig. 2a) and hypointense on T1s. On diffusion-weighted imaging (DWI) it showed restricted diffusion and no loss of signal intensity on out-of-phase images (compared with in-phase) (Fig. 2b, 3).

Dynamic MR scanning revealed an early intense enhancement in the arterial and following phases, saving millimetric central foci that remained hypointense (Fig. 4).

6 months later, a new MR was carried out showing an increase in size (Fig. 5) because of it, surgery was decided. Histological study confirmed the diagnosis of myxoid adrenocortical carcinoma.

Discussion

Within the group of adrenal cortical neoplasms there is an extremely rare variant characterized by its myxoid component, first being described in 1979 by Tang et al. Less than 70 cases of myxoid adrenal neoplasms (MAN) have been reported in the literature including myxoid adrenal carcinomas (MAC), myxoid adrenal adenomas (MAA) and myxoid adrenal borderline tumours [1, 2].

The true clinical behaviour of MAN is difficult to assess. MAN can cause both absence of symptoms or alteration of hormone levels (Cushing symptoms) or even abdominal pain due to invasion of other organs.

Discard an adrenal adenoma is the first step to establish the diagnosis. In case of MAN, a non-contrast CT would show attenuation values >10 HU and in contrast-enhanced CT examination, after 15 minutes, more than 30 HU [3].

When CT findings are inconclusive (lesions with 10-25 HU could be lipid poor adenomas), an MR should be carried out. Due to the high water content of the myxoid material and the absence of cytoplasmic fat we could see hypointense signal on T1-weighted images and hyperintensity on T2s. Out-of-phase images may be useful to differentiate between a lipid poor adenoma and a MAN, which shows no loss of signal intensity compared with that on in-phase. Restriction on DWI (b = 1000 s/mm2) is also seen [4, 5].

The prognosis of MAN depends on its histological findings. MAA presents 100% of survival rates. However, MAC presents a high tendency to local growth and distant metastases in lung and liver with mortality between 70% and 90% [1]. Surgery is the basis of treatment, however, this option would only be considered if the lesion is large enough (> 2 cm) or if an increase of size is noticed, as in this case. Chemotherapy should be considered in case of a metastatic MAC.

Although it is a very rare entity with scarce published literature, it is important to include the MAC in the differential diagnosis of an adrenal lesion due to its poor prognosis. Keep in mind that it is the myxoid component of the neoplasm that determines its radiographic findings.

Differential Diagnosis List

Final Diagnosis

Myxoid adrenal carcinoma.

URL:	https://www.eurorad.org/case/14384
DOI:	10.1594/EURORAD/CASE.14384
ISSN:	1563-4086