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RCR RADIOLOGY CASE REPORTS
Case Report
Ectopic adrenocortical adenoma in the renal hilum mimicking a renal cell carcinoma
Masashi Endo, MDª, Hiroyuki Fujii, MD, PhDª,*, Akifumi Fujita, MD, PhDa, Tatsuya Takayama, MD, PhDb, Daisuke Matsubara, MD, PhDc, Tomohiro Kikuchi, MDª, Saki Manaka, MDª, Harushi Mori, MD, PhDª
a Department of Radiology, Jichi Medical University, School of Medicine, Tochigi, Japan
b Department of Urology, Jichi Medical University, School of Medicine, Tochigi, Japan ” Division of Integrative Pathology, Jichi Medical University, School of Medicine, Tochigi, Japan
ARTICLE INFO
Article history: Received 29 August 2021
Revised 14 October 2021 Accepted 17 October 2021
Keywords:
Ectopic adrenal gland adrenocortical adenoma renal cell carcinoma
ABSTRACT
Ectopic adrenocortical tissue can arise along the path of embryonic migration, such as the celiac axis, broad ligament, adnexa of the testis, and spermatic cord. Occasionally, ectopic adrenocortical tissues undergo marked hyperplasia and develop into ectopic adrenocortical adenomas. This report describes the case of a 60-year-old man who was incidentally found to have a lipid-containing mass with early enhancement and delayed washout in the right renal hilum. A renal cell carcinoma was suspected, and robot-assisted partial nephrectomy was performed, but the final diagnosis was an ectopic adrenocortical adenoma. We should include ectopic adrenocortical adenoma in the differential diagnosis when we find a lipid- containing tumor adjacent to the kidney.
@ 2021 The Authors. Published by Elsevier Inc. on behalf of University of Washington. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
Introduction
Ectopic adrenocortical tissue is a developmental abnormality of the adrenal gland. It can arise along the path of embry- onic migration, such as the celiac axis, broad ligament, ad- nexa of the testis, and spermatic cord [1]. Occasionally, ectopic adrenocortical tissues undergo marked hyperplasia and de- velop into ectopic adrenocortical adenomas and carcinomas [2]. A case of an ectopic adrenocortical adenoma in the renal hilum that mimicked a renal cell carcinoma (RCC) is reported.
Case report
A 60-year-old man presented to our hospital for further ex- amination of a nodular shadow in the left middle lung field found on a chest X-ray performed during a general checkup. He had a history of hypertension diagnosed at the age of 55 years and had received drug therapy from a local physician. His blood pressure was 137/80 mm Hg, and the remainder of the physical examination was unremarkable. Serum sodium and potassium levels were normal.
# Competing Interests: The authors declare that there is no conflict of interest regarding the publication of this paper.
* Corresponding author E-mail address: hiroyuki.fujii@jichi.ac.jp (H. Fujii).
https://doi.org/10.1016/j.radcr.2021.10.038
1930-0433/ 2021 The Authors. Published by Elsevier Inc. on behalf of University of Washington. This is an open access article under the
We re-examined the chest X-ray, but no nodular or mass shadow was found. Noncontrast chest computed tomogra- phy (CT) also showed no remarkable findings in his lungs. However, a well-defined, homogeneous, low-density mass (CT value: 15 Hounsfield Units), 2.3 × 2.3 × 2.1 cm in size, was in- cidentally found in the right renal hilum. The mass was par- tially in contact with the right renal cortex. Dynamic contrast- enhanced abdominal CT demonstrated that the mass showed slight enhancement in the arterial phase and washout in the delayed phase (Fig. 1). Bilateral adrenal glands showed no ab- normalities. There was no continuity between the adrenal gland and the mass. On magnetic resonance imaging (MRI), T1-weighted gradient echo images showed a uniform de- crease in signal intensity on the out-of-phase images com- pared with the in-phase images, which indicated distribution of a microscopic fat component within the mass (Fig. 2). On the apparent diffusion coefficient maps derived from diffusion- weighted imaging (DWI) with a b value of 1000 s/mm2, the mass showed lower intensity than the renal cortex. Based on these imaging findings, RCC was diagnosed because the mass was thought to originate from the renal cortex, and have mi- croscopic fat component.
Robot-assisted partial nephrectomy was performed. Intra- operative findings showed that the mass was in contact with the right kidney, as suggested by the imaging findings. How- ever, the mass was loosely attached to the kidney, and briefly removed. Although there was no apparent residual lesion on the surface of the kidney, a part of the kidney in contact with the mass was resected. The histopathological findings showed an adrenocortical neoplasm without capsule, and the tumor was distant from the native adrenal gland. According to the Weiss criteria, the adrenocortical neoplasm was benign, and the Ki-67 labeling index was approximately 1%. The final di- agnosis was an ectopic adrenocortical adenoma arising from adrenal rest tissue in the renal hilum (Fig. 3).
The patient’s postoperative course was uneventful. Blood pressure and serum electrolyte levels did not change signif- icantly. There was no recurrence at evaluation 2 years after surgery.
Discussion
A case of an ectopic adrenocortical adenoma in the renal hilum that mimicked an RCC was described. To the best of our knowledge, there have been few cases of ectopic adreno- cortical adenomas located in the renal hilum reported in the literature.
The adrenal gland consists of 2 parts, the cortex, and medulla. The adrenal cortex arises from the coelomic meso- derm of the urogenital ridge at the fifth week of gestation. By the eighth week of gestation, the cortical mass separates from the rest of the mesothelial tissue. The adrenal medulla arises from neural crest tissue in the adjacent sympathetic ganglion at the level of the coeliac plexus. The neural crest tissues mi- grate toward the adrenal cortex at the seventh week of gesta- tion, and they gradually invade the cortex.
Ectopic adrenal glands may form when fragments of the cortical cells break off during development. The ectopic adrenal gland may contain cortex and medulla or only cortex, depending on whether the fragments break off before or after the invasion of the medullary tissue into the cortex. Ectopic adrenal tissue is found in up to 50% of neonates, but most of them regress in early infancy [3]. The prevalence of ectopic adrenal tissue in adults was reported to be 1% [4]. The ectopic adrenal tissue can occur anywhere in the migration path de- scending with the gonads, including in the retroperitoneum, testis, broad ligament, kidneys, ovaries, and inguinal region. The most common reported sites of ectopic adrenal tissue are the celiac axis region (32%), broad ligament (23%), adnexa of the testis (7.5%), and the spermatic cord (1.2%) [1]. An ectopic adrenal gland has been rarely reported in the lungs, stomach, and even in the intradural space and brain [5].
Occasionally, ectopic adrenocortical tissues undergo marked hyperplasia and develop into ectopic adrenocortical adenomas and carcinomas [2]. Although most ectopic adrenal tissues were non-functional, few ectopic adrenocortical tu- mors can produce hormones such as cortisol, aldosterone, or androgens, which can lead to the patient presenting with Cushing’s syndrome or hyperaldosteronism, or it can produce extreme virilization [6]. The patient in the present case had
50 um
3
hypertension, but corticosteroid levels were not measured because an ectopic adrenocortical tumor was not included in the differential diagnosis before surgery.
Diagnostic imaging, such as CT and MRI, is important to detect ectopic adrenocortical tumors. Although it is challeng- ing to diagnose an ectopic adrenocortical adenoma preopera- tively, imaging features of adrenocortical adenoma could as- sist in the diagnosis. On noncontrast CT, an adrenocortical adenoma often appears low density due to its high lipid con- tent [7]. A dynamic study often shows rapid contrast enhance- ment and washout [8]. On MRI, chemical shift imaging is a reliable sequence for diagnosing adrenocortical adenoma, es- pecially when it is not hypodense on noncontrast CT. Chem- ical shift images show decreased signal intensity on the out- of-phase image compared with that of the in-phase image, which indicates a microscopic fat component within the ade- noma [9]. However, these imaging features also apply to RCC. In previous studies, a signal intensity decrease was observed in 60%-80% of clear cell RCC due to its intracellular lipid[10,11]. Other than clear cell RCC, microscopic fat is also found in fat-poor angiomyolipoma (AML), papillary RCC, chromophobe RCC, and oncocytoma [11]. Macroscopic fat is found in classic AML, Wilms tumor [12], and rarely in RCC [13]. On DWI, the ADC values are reported to not be valuable in the differentia- tion of adrenocortical adenomas, and metastases because of the overlapping of ADC values [14].
To date, there have been 6 cases of ectopic adrenocortical adenoma in the renal hilum [6,15-19]. The patients (2 males, 4 females) ranged in age from 27 to 63 years, with tumor sizes of 2.5-5.3 cm. Of the 6 cases, 3 had continuity with the kidney [6,15,16], and 5 reported endocrine abnormalities, including Cushing’s syndrome [6,15-17], borderline elevation of testos- terone [18], and hyperaldosteronism [6]. Most of them were correctly diagnosed due to their endocrine abnormalities. The remaining one case was a non-functioning ectopic adrenocor- tical adenoma in the left renal hilum [19]. The possibility of ec- topic adrenocortical adenoma was not considered due to the lack of hormonal abnormalities. Because the mass was clearly located apart from the renal parenchyma, a benign retroperi- toneal tumor was suspected. In the present case, the mass was thought to originate from renal cortex, and there were no symptoms to suspect hormonal abnormalities other than hypertension. Therefore, it was difficult to differentiate an ec- topic adrenocortical adenoma from clear cell RCC preopera- tively.
In conclusion, a case of an ectopic adrenocortical adenoma in the renal hilum that mimicked an RCC was described. Al-
though less frequent, we should include ectopic adrenocor- tical adenoma in the differential diagnosis when we find a lipid-containing tumor adjacent to the kidney. Furthermore, measurement of hormone levels could assist in making the diagnosis.
Patient consent
Informed consent was obtained from the patient for the pub- lication of this case report.
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