Adrenocortical carcinoma with fat inclusion: case report
S. Heye,1 H. Woestenborghs,2 F. Van Kerkhove,1 R. Oyen1
1Department of Radiology, University Hospitals Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
2Department of Anatomopathology, University Hospitals Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
Abstract
Adrenocortical carcinoma is a rare tumor that arises from the adrenal cortex, with an estimated incidence of 0.5% to 2% per 1 million patients yearly. Although some fat content can be expected in hormonally active adre- nocortical carcinomas, areas of 100% fat are extremely rare. We present a case of an adrenocortical carcinoma with a small focus of pure fat depicted on magnetic resonance imaging.
Key words: Neoplasms, adrenal gland-Neoplasms, adrenal cortex-Carcinoma, adrenal cortical-Fat, mag- netic resonance-Adipose tissue
Adrenocortical carcinoma (ACC) has rather typical features on magnetic resonance imaging (MRI) such as internal hemorrhage, central necrosis, and peripheral enhancing nodules [1]. Some signal loss on out-of-phase images has been reported in hormonally active ACCs, likely due to areas of functional adrenal tissue that contain fat and water tissue. Areas that contain only fat are extremely rare, with only one case previously re- ported [2], and make differential diagnosis with myelo- lipoma difficult.
Case report
A 38-year-old male presented with hypertension and presyncopal episodes of nausea, paresthesia in both hands and feet, bioccipital headaches, and bilateral se- vere tinnitus.
The frequency of these symptoms increased and the severity of the complaints exacerbated during the next 2 weeks. Laboratory results showed low levels of potas- sium for which medication was started. To exclude an
adrenal mass lesion, ultrasonography of the abdomen was performed. On ultrasound (not shown), a large nodular mass, predominantly hypoechoic but with a hyperechoic center, was found in the left adrenal area. For further lesion characterization and staging MRI were performed.
On T2-weighted MR images, a heterogeneous mass was seen in the left adrenal region, displacing the left kidney (Fig. 1). On T1-weighted images there was a hy- perintense area present in the lesion (Fig. 2), without signal intensity loss in its center but with a hypointense halo on opposed phase images (not shown). This lesion disappeared on the fat-saturated images (Fig. 3).
After intravenous administration of gadolinium, the mass showed peripheral enhancement in the arterial phase and heterogeneous enhancement in the venous phase (not shown).
These imaging findings suggested an adrenocortical carcinoma with an area of pure fat. Laparoscopic resection was performed. The resected specimen mea- sured 7 × 4.9 × 4.3 cm and weighed 145 g. Histologic examination of the specimen showed an adrenocortical carcinoma without evidence of vascular invasion but with a focus of mature adipose tissue (Fig. 4) that mea- sured 1.5 × 0.7 cm. Myeloperoxidase staining to detect foci of myeloid cells was negative. Postoperative recovery was uneventful.
Discussion
ACC is a rare adrenal tumor that arises from the adrenal cortex. The annual incidence is estimated 0.5% to 2% per 1 million patients [3-5]. It presents a bimodal age dis- tribution, with a first peak occurring before age 5 years and a second peak in the fourth to fifth decade of life [3]. In general, ACCs in childhood tend to have a better prognosis because they present with a hormonal syn- drome, allowing earlier detection and, hence, treatment [3]. ACCs are bilateral in 2% to 6% of cases [3].
Fifty percent to 62% of ACCs are functional [3, 6] and cause endocrine symptoms such as primary hyper- aldosteronism (Conn syndrome), Cushing syndrome, and adrenogenital syndrome (virilization or feminiza- tion), depending on the cortical zone from which the tumor originates [4].
The most common syndrome associated with ACC in adults is Cushing syndrome [3], with typical clinical symptoms including weight gain and centripetal obesity, muscle waisting, hypertension, acne, hyperglycemia, and
osteoporosis. Hirsutism and oligomenorrhea are often present in patients with a component of virilization. In childhood, virilization is the most common hormonal syndrome.
Other, more aspecific symptoms are anorexia, abdominal pain and a palpable mass.
Several hormonal tests can be used to establish or confirm excessive steroid secretion.
Ultrasound can be used to identify adrenal masses, but it is not specific and is largely operator dependent. Most adrenal masses appear as rounded, rather well- circumscribed solid masses [3].
Computed tomography (CT) demonstrates a solid mass, usually large at presentation, with a diameter ranging from 4 to 10 cm, and central necrosis is common. Calcification has been described in 20% to 30% of cases [4, 6]. Small lesions may be homogeneous on unenhanced CT, but usually there is heterogeneous peripheral enhancement on contrast-enhanced series [6]. CT can also depict the extent of local invasion [3] including extension of tumor into the renal vein or inferior vena cava, which is a rather common finding. CT can also show distant metastases.
On MRI, ACC usually has a heterogeneous hyper- intensity on T1- and T2-weighted images due to internal hemorrhage and necrosis. There is patchy enhancement after intravenous gadolinium, with nodular zones of in- tense enhancement and areas without enhancement [1, 5]. Sparse amounts of fat have been reported in hormonally active ACCs, presenting as a signal intensity loss on opposed phase images.
In the present case, a small focus of pure fat was demonstrated in an ACC on the fat-saturated images. The opposed phase images showed no decrease in signal intensity, but rather a chemical shift artifact, a feature of tissue composed of pure, mature fat. This is a very rare
finding, rendering differential diagnosis with myelolip- oma difficult. The imaging features of this benign adrenal tumor are considered characteristic on ultrasound, CT, and MRI and are based on the large amount of mature fat in the lesion [4, 6].
Otal et al. use the term collision tumor for indepen- dently coexisting neoplasms in an adrenal mass without significant tissue admixture [7]. Myelolipomatous foci are commonly seen in the adrenal gland in Cushing disease but currently are more frequently reported in adrenal adenoma [7]. These findings suggest that the presence of fat is not always specific for myelolipoma, and that other imaging characteristics of the adrenal mass are important. In such cases, the diagnosis of my- elolipoma must be made with caution, especially when other findings such as size, necrosis, peripheral and het- erogeneous enhancement, and the paucity of the fatty
component are more likely to be suggestive of a malig- nant lesion. In these cases, the lesion should be managed as a malignant tumor.
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