An ectopic adreocortical adenoma of the renal sinus: a case report and literature review

Ectopic adrenal tissue is estimated to occur in about 1 % of the adult population and up to 50 % of neonates [3]. It regresses usually in early infancy. The adrenal cortex is derived from the coelomic mesoderm of the urogenital ridge at the 5th week of gestational age and is separated at the 8th week. Ectopic adrenal tissue occurs when a fragment of the primitive adrenal gland sheds off during development. It may come to rest in any visceral organs, especially the kidneys, liver, and gonads. Rarer sites include the lung, spinal region, stomach, and brain [1, 4]. Ectopic adrenal tissue contains cortex and medulla if the breaking event occurs after the migration of neural crest tissue into the cortex. Otherwise, only cortex exists in ectopic adrenal tissue.

Most ectopic adrenal tissue has no obvious physiological function and causes no clinical symptoms. Few ectopic adrenal tumors can produce hormones. However, this can lead to physical changes such as hypertension, feebleness, crinosity, and palpitations. The reported case involved abnormal blood glucose, cortisol, and aldsterone levels, and obvious clinical symptoms. It should be considered a functional ectopic adrenal tumor. CT is sensitive enough to indicate the locations of ectopic adrenal masses. However, it can be difficult to determine whether a mass is inside or outside of the renal pelvis if it is adjacent to renal sinus. In these cases, CTA can help determine the exact location. It is especially effective in the description of the relationship between mass and surrounding vessels, which is very important for this type of surgery.

Differentiating between benign and malignant ectopic adrenal tumor is a challenge. Routine pathological examinations are sometimes not always enough. Tumor weight and size, hormone levels, signs of vascular invasion, and high mitotic index are useful morphologic indicators to evaluate the carcinogenic potential. Large tumors (more than 100 g in weight or 5.0 cm in diameter), invasion of surrounding tissues, and presence of metastasis, are indicators of malignancy [5, 6]. In addition, malignant tumor presents more commonly a mixed Cushing-virilization syndrome. The tumor in this report was much smaller than 100 g in weight and 3.4 cm in diameter. Only abnormal cortisol and aldsterone levels were detected. The tumor was completely resected from the renal sinus with an intact capsule. No invasion of surrounding tissues was detected. All signs indicated the benign tendency of this mass. Recently, some molecular markers have been used to differentiate adrenal carcinoma from benign tumors [7]. These new markers may help to distinguish the nature of tumor in the future.

The treatment of ectopic adrenal tumors includes conservative therapy and radical resection (open or minimally invasive surgery). If the tumor is small or nonfunctioning, watchful waiting is enough. Otherwise, the tumor should be resected although evincing no malignant tendency. In our study, the large tumor size (3.4 cm in diameter) and obvious clinical symptoms can serve at surgical indications. However, the procedure is complicated and difficult because tumors in the renal sinus are surrounded by the renal artery, renal vein, and ureter. Common complications include uncontrolled bleeding and side injury of renal pelvis or ureter. The choice of a surgical approach should depend on the surgeon’s experience.

In summary, ectopic adrenal tumors of the renal sinus are rare and difficult to diagnose and treat. For large or functional tumors, complete resection should be performed. The procedure can be difficult if the tumor is located deep in the renal sinus. The decision to perform an open or minimally invasive surgery should be made according to the surgeon’s experience.