Didem Öncel Yakar1, Ercan Karaarslan2, Tarık Terzioğlu3

1Acıbadem Hastanesi, Genel Cerrahi AD, İstanbul
2Acıbadem Üniversitesi, Radyoloji AD, İstanbul
3Amerikan Hastanesi, Genel Cerrahi AD, İstanbul

Keywords: Adrenal gland, incidentaloma, ganglioneuroma

Abstract

The probability of finding an incidentaloma has rapidly increased with the widespread usage of abdominal imaging modalities, creating a challenge to identify the rare functioning or malignant adrenal tumor that should be removed while avoiding unnecessary testing and surgery in the majority of patients whose adrenal lesion is nonfunctioning and benign. We report a case of a woman who presented with a non-functional left-sided adrenal tumor that was postoperatively diagnosed as ganglioneuroma with emphasis on radiologic findings. Awareness of specific characteristics of this rare entity may facilitate the differential diagnosis of adrenal masses.

Introduction

With the developments in and frequent usage of abdominal imaging procedures the rate of detection of clinically silent adrenal masses, which are the most common adrenal disorders, has increased dramatically presenting a challenge to endocrinologists, endocrine surgeons, pathologists and radiologists(1, 2). Evaluation of the patient with adrenal incidentaloma requires an understanding of the differential diagnosis of adrenal masses, the biochemical profile of hyperfunctioning adrenal tumors, risk factors for adrenal malignancy and treatment modalities(3). Herein we present a case of ganglioneuroma, which is one of the rare causes of incidentalomas with specific emphasis on its radiological properties.

Case Presentation

A 40 years old female was referred for further evaluation of a left sided adrenal tumor, incidentally detected by abdominal ultrasonography for unrelated reasons. She had no prior medical history and her systemic examination was entirely normal. Laboratory results were all within the reference range, including values of potassium, cortisol, vanillylmandelic acid, adrenalin and noradrenalin levels, as well as normal urinary catecholamines and metanephrines. Her non-contrast abdominal computed tomography showed a well-defined, non-enhanced, 8x5.8 cm left adrenal tumor (Fig. 1). The density of the tumor was less than that of muscle. The tumor was poorly enhanced with contrast medium. On T1-weighted MRI, the tumor was visualized as a homogenous mass with signal intensity similar to that of the spleen. The tumor showed no signal suppression on chemical shift imaging and only focal enhancement areas in the center of the lesion (Fig. 2-4). On T2-weighted MRI, it was seen as a heterogenous mass with high signal intensity (Fig. 5).

She was operated on with a diagnosis of nonfunctional incidentaloma and a left adrenalectomy via a subcostal approach was performed. Her intraoperative findings revealed no additional pathology. She had an uneventful recovery thereafter and was discharged on the third postoperative day.

Her pathologic examination revealed a ganglioneuroma. The tumor was 8x8x3.5 cm in size, weighing 210 gr. Her microscopic examination showed encapsulated, mature ganglion cells scattered throughout a base composed of spindle cells and acidophyllic bundles. The spared adrenal medulla and cortex showed no pathology.
She is being followed up for 50 months with no further problems.

Discussion

Adrenal incidentalomas are defined as asymptomatic adrenal masses detected during non-related reasons. Between 1 to 4% of all abdominal imaging studies reveal an unexpected adrenal tumor. The prevalence of true incidentalomas (excluding extra adrenal primary malignancy, adrenal hemorrhage and known hypersecretion) varies from 0.6 to 1.3% of all abdominal CT scans(4). The majority of these tumors are benign, non-functioning cortical adenomas. Lesions presenting as incidentalomas also include adrenocortical carcinoma, cortisol producing adenoma, aldosteronoma, sex hormone secreting tumors, pheochromocytoma, metastatic tumors and other less common adrenal lesions. Within this rare group of ‘other lesions’ are cysts, myelolipomas, hemorrhage and ganglioneuromas(1, 2). While the majority of incidentalomas can be safely observed, operative management is required for patients with functioning tumors and tumors that are more likely to be malignant.

Ganglioneuroma is a relatively rare benign tumor of neural crest origin mostly arising in the posterior mediastinum and retroperitoneum. It is located in the adrenal glands in 20% of the cases. It predominantly occurs in children and young adults, with a median diagnostic age of 7 years. There is a slight female predominance, 1.5:1 (5). They characteristically do not secrete catecholamines or steroid hormones, therefore remaining asymptomatic. However they may grow to relatively large sizes and cause symptoms due to local expansion and pressure on adjacent structures. When they grow to large sizes an abdominal mass can be palpated, which is the most common sign. Although not typical, secretion of catecholamines and steroid hormones has also been reported(5, 6). Another uncommon entity of this group is the compound adrenal tumors of pheochromocytoma and ganglioneuroma(7). It has recently been reported that ganglioneuroma is a rare but not unexpected finding also in the MEN 2 syndromes (8). Upon detection of these masses, surgical excision is both diagnostic and curative.

Ganglioneuroma is usually detected incidentally by abdominal imaging studies ordered for unrelated reasons. At CT or MR imaging they appear as well-circumscribed oval, crescentric, or lobulated masses. They also tend to surround major blood vessels without compromising the lumen, which differentiates them from carcinomas. Contrast material enhancement is variable(9). Although CT does not seem to be useful for tumor characterization, it might reveal calcifications like in other neurogenic tumors(10). At MRI they appear as homogenous, low signal intense masses on T1-weighted images, and as heterogeneous, high signal intense lesions on T2-weighted images. Although the reason of this heterogeneity on T2-weighted images is not known clearly, it is suggested that this feature may help distinguish adrenal ganglioneuroma from other adrenal masses, especially if associated with a whorled pattern(10- 12). This whorled-pattern is thought to correlate with the amount of Schwann cells and collagen fibers, in the largest series of adrenal ganglioneuromas the authors reported 1 case of whorled pattern out of the 8 cases10. The T2-weighted images as in and out-phase chemical shift imaging shows no absolute change in signal intensity(13).

The gross pathologic evaluation of ganglioneuroma reveals white to yellow, sharply circumscribed tumors, with variable consistency and that may appear encapsulated; in fact they frequently lack a true capsule. Histopathologically, the tumor is composed entirely of ganglion cells and Schwann cells, together with variable amounts of collagen(14). By definition it does not contain neuroblasts, intermediate cells, or mitotic figures. Although some neuroblastomas and ganglioneuroblastomas may mature to ganglioneuromas, the presence of neuroblasts excludes the diagnosis of ganglioneuroma. The case presented herein did not show any specific clinical finding suggesting the diagnosis of ganglioneuroma but the radiological findings were consistent with those of ganglioneuroma. The pathologic evaluation revealed the final diagnosis.
Ganglioneuroma is an uncommon silent lesion, lacking specific laboratory findings. Imaging findings, on the other hand, might raise suspicion with some clues, but the diagnosis of adrenal ganglioneuroma requires either biopsy or surgical removal. Surgical excision provides diagnosis and result in cure in almost all instances. On the era of minimally invasive surgery, the patients might benefit from a preoperative diagnosis of this benign adrenal mass rather than having an aggressive oncologic adrenalectomy.

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