Ectopic adrenocortical adenoma in the renal hilum: a case report and literature review

Abstract

Background: Ectopic (accessory) adrenocortical tissue, also known as adrenal rests, is a developmental abnormality of the adrenal gland. The most common ectopic site is in close proximity to the adrenal glands and along the path of descent or migration of the gonads because of the close spatial relationship between the adrenocortical primordium and gonadal blastema during embryogenesis. Ectopic rests may undergo marked hyperplasia, and occasionally induce ectopic adrenocortical adenomas or carcinomas.

Case presentation: A 27-year-old Chinese female patient who presented with amenorrhea of 3 months duration underwent computed tomography urography after ultrasound revealed a solitary mass in the left renal hilum. Histologically, the prominent eosinophilic tumor cells formed an alveolar- or acinar-like configuration. The immunohistochemical profile (alpha-inhibin+, Melan-A+, synaptophysin+) indicated the adrenocortical origin of the tumor, diagnosed as ectopic adrenocortical adenoma. The patient was alive with no tumor recurrence or metastasis at the 3-month follow-up examination.

Conclusions: The unusual histological appearance of ectopic adrenocortical adenoma may result in its misdiagnosis as oncocytoma or clear cell renal cell carcinoma, especially if the specimen is limited. This case provides a reminder to pathologists to be aware of atypical cases of this benign tumor. Although uncommon, an ectopic adrenal lesion should be included in the differential diagnosis of tumors involving the renal hilum. A misdiagnosis of this benign condition as a malignant renal tumor may have severe consequences for the patient, including unnecessary radical nephrectomy. Preoperative biopsy and appropriate immunohistochemical staining will assist in determining the origin and nature of the tumor and in avoiding intraoperative uncertainty.

Keywords: Ectopic adrenal gland; Ectopic adrenocortical adenoma; Ectopic oncolytic adrenocortical neoplasm; Oncocytes; Renal hilum.

Fig. 1

Imaging examination results of the patient. a Computed tomography (CT) urography and three dimensional reconstruction show the ureters bilaterally, without any obvious expansion. Enhanced CT and coronal reconstruction showing b a soft-tissue mass with a maximum diameter of 2.7 cm in the left renal hilum, near the renal pelvis and c an atrophic bilateral adrenals in sagittal view

Fig. 2

Histological features. The tumor is circumscribed by a discontinuous capsule (a) and is clearly demarcated from the surrounding adipose tissue (b). c The tumor cells are mainly arranged in nests with an alveolar- or acinar-like configuration. These acini are surrounded by an open vascular network. d Foci of edematous stroma are seen within the tumor. e The focal infiltration of mature lymphocytes is especially prominent in the areas undergoing lipomatous or myelolipomatous metaplasia. f Bizarre nuclear forms are occasionally present, especially in the area of diffuse oncocytes. The cells contain eosinophilic nuclear pseudoinclusion bodies. g Lipofuscin pigmentation is detected in focal areas. h The peripheral adipose tissue contains foci of ectopic adrenal rests

Fig. 3

Immunohistochemical staining. a The tumor cells are markedly and diffusely positive for alpha-inhibin. Their cytoplasm shows positive staining for b Melan-A and c synaptophysin. d Diffuse fine granular reactivity with an anti-mitochondrial antibody is seen in eosinophilic cells