During the approach to management of an adrenal mass, it is important that the practitioner distinguishes between a benign versus malignant tumor. Primary adrenal malignancy is extremely rare, and there has not been much progress in the nonsurgical aspect of its management. Proper surgical management with maintenance of the tenets of oncologic resection is the primary treatment for localized adrenal malignancy. If malignancy is not considered and improper surgical management follows, the surgeon can severely compromise the opportunity for cure.
A definitive diagnosis of adrenal malignancy is usually not made until after histopathologic examination of the resection specimen; thus, it is important that a healthy preoperative suspicion of malignancy guides the appropriate approach to surgical management. Preoperative suspicion for malignancy should be based on clinical, biochemical, and radiologic criteria.
Adrenal masses are among the most frequently discovered incidental lesions and are found at a rate of 5% on cross-sectional imaging. Regardless of why the adrenal mass was found, malignancy should always be considered in the differential diagnosis. Radiologic characterization of the adrenal mass will aid in an accurate diagnosis.
Characterization as either benign or malignant is an imperative step in the workup of the adrenal mass. Advances in radiologic imaging techniques allow the accurate characterization of an adrenal mass in most circumstances.
Tumor size is an important predictor of malignancy and is easily assessed by most techniques. Increasing tumor size imparts a higher risk of malignancy. Incidentally found adrenal tumors smaller than 4 cm have an approximate 2% risk of primary adrenocortical carcinoma (ACC), but tumors larger than 6 cm have a more than 25% risk of ACC. The risk of ACC approaches 98% in tumors larger than 10 cm.
Computed tomography (CT) is the current modality of choice for adrenal imaging. The majority of benign adenomas contain a large proportion of lipid content. Low-density fat molecules cause low attenuation on noncontrast CT images. A value of less than 10 Hounsfield (noncontrast) units is largely accepted to diagnose a lipid-rich adenoma with a sensitivity of 71% and specificity of 98%. However, the lipid content of benign adenomas is variable, and up to 30% are lipid poor. This fact combined with the low diagnostic sensitivity of noncontrast CT has led to the use of adrenal protocol CT, noncontrast, and contrast images with delays to assess contrast washout to determine the full character of an adrenal mass. Benign adenoma, both lipid rich and lipid poor, have fast contrast washout after the administration of intravenous (IV) contrast. Adrenal protocol CT with delayed images 15 minutes after administration of IV contrast allows for the interpretation of adrenal mass washout, and this method has a 98% sensitivity and 92% specificity for distinguishing adenomatous from nonadenomatous adrenal tumors using an absolute percent washout of 60% or higher and relative percent washout of 40% or higher. The adrenal CT with washout is able to more accurately diagnose benign adenoma than noncontrast CT alone and is now the generally preferred method of adrenal imaging. Pheochromocytoma represents an occasional exception to the rule and may display high washout values on adrenal CT.
Characteristics such as large tumor size, lack of well-defined tumor margins, heterogeneous appearance, central low attenuation (necrosis), direct invasion into adjacent organs, renal vein or inferior vena cava (IVC) invasion, and retroperitoneal lymphadenopathy all suggest malignancy on cross-sectional adrenal imaging.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) characterization is usually used secondarily to CT and reserved for select patients. Indications for primary use of MRI to characterize an adrenal mass include its use in pregnant women, to characterize a suspected pheochromocytoma, and in those with contraindications to the use of IV contrast.
Positron Emission Tomography
Fluorodeoxyglucose (FDG) positron emission tomography computed tomography (PET-CT) allows for very sensitive and specific (97%–100% and 91%–98%, respectively) characterization of benign versus malignant adrenal lesions. FDG-PET/CT is a useful modality when characterization of an adrenal lesion is indeterminate by conventional CT. It is also useful in the staging of adrenal malignancy with the capability of identifying lesions as small as 5 mm.
Sonographic visualization of the adrenal gland in adults is limited by patient size and presence of bowel gas. However, contrast-enhanced sonography using microbubble contrast has begun to show some promise. Although not yet common practice, contrast-enhanced sonography can aid in the characterization of larger adrenal masses. Early studies are using the pattern of contrast enhancement and the time to contrast washout as a marker for adenomatous and nonadenomatous adrenal masses.
Adrenocortical carcinoma is rare with an incidence of 1 to 2 per million population diagnosed annually. ACC has a bimodal age distribution with the vast majority of cases diagnosed in the sixth decade of life (median age, 55 years), but a small percentage are diagnosed before 5 years of age. Women may be more commonly affected with a female-to-male ratio of 1.6 to 1.
Approximately 60% of patients with ACC have functional tumors and an associated endocrinopathy. Cushing syndrome represents the most common endocrinopathy associated with functional ACCs. Women with virilization from androgen-only secreting tumors are next most common followed by males with feminization from estrogen-only secreting tumors. Hyperaldosteronism is the least common endocrinopathy and represents only about 5% of functional ACCs. ACC does have the potential to hypersecrete multiple hormones, and this can occur in up to 10% of functional ACCs. The average tumor size at time of diagnosis is 10 to 15 cm. There has been no stage migration toward lower stage disease or smaller tumor size at the time of diagnosis over the past few decades despite the common and frequent use of cross-sectional imaging.
The prognosis for patients with ACC has remained largely unchanged over the past 3 decades. The median survival time of all patients presenting with ACC is approximately 2 years, and for patients who present with disease amenable to surgical resection, the 5-year survival rate is approximately 40%. The median survival time for stage I disease is longer than 10 years, but the median survival of stage IV disease (distant metastasis) is less than 1 year after diagnosis. Factors associated with a higher risk of death include advanced age, poorly differentiated tumors, positive surgical margins, and lymph node or distant metastasis.
Surgical resection is the mainstay of treatment for patients with localized ACC and is the only curative option. The initial resection often times remains the patient’s only opportunity at cure; a positive margin or incomplete resection ultimately leads to recurrence and metastatic spread of disease. The main principle of ACC resection is maintaining the tumor capsule integrity with an en bloc removal of the tumor to prevent tumor spillage.
The majority of neuroendocrine tumors that secrete catecholamines arise from the adrenal medulla and are referred to as pheochromocytomas , but about 15% arise from extra-adrenal autonomic neural ganglia and are referred to as paragangliomas . Pheochromocytoma is a rare neoplasm with an incidence of 2 to 8 per million population annually. Pheochromocytoma is typically diagnosed in the fifth or sixth decade of life in sporadic cases. Those with inherited genetic syndromes, multiple endocrine neoplasia syndrome 2A and 2B, von Hippel-Lindau syndrome, and neurofibromatosis type 1 may present at an earlier age. Male and females are equally affected by the disease.
Traditional teaching dictates pheochromocytoma follows the rule of 10: 10% malignant, 10% bilateral, and 10% familial. However, recent studies report a higher malignancy rate of up to 50%. Because of the lack histopathologic criteria for the diagnosis of malignant pheochromocytoma, the only method of diagnosis is the presence of metastasis in an area of the body where neuroectodermal tissue is not generally present. Common areas of metastasis are the axial skeleton, liver, lungs, lymph nodes, and kidneys.
Surgical removal of pheochromocytoma is the preferred treatment, and although it is not curative in cases of malignant or metastatic disease, treatment may still be of use in palliating symptoms of catecholamine excess. Preoperative adrenergic blockade is paramount in completing surgery safely, and minimizing manipulation of the tumor during surgery prevents dangerous catecholamine surges intraoperatively.
The adrenal gland is a common site of metastasis for primary lung, gastrointestinal, breast, and renal carcinomas. However, isolated metastasis to the adrenal gland with no other evidence of metastasis or locoregional spread is extremely rare. In such cases of isolated metastasis, metastasectomy of the adrenal gland and the attendant tumor provide the patient a survival benefit. Before surgical excision, thorough radiologic staging to identify other locations of recurrence or metastasis is necessary. Metastasis to the adrenal gland is usually well encapsulated, allowing for laparoscopic surgical excision.
Open Adrenal Excision
Multiple open surgical approaches are available to successfully remove adrenal masses. Factors such as suspected malignancy, tumor size, tumor location, patient body habitus, previous surgeries, and surgeon experience and preference influence the preferred surgical approach. Suspected adrenal malignancy, particularly adrenocortical carcinoma, is an indication for open adrenalectomy, and the open surgical approach should be considered for tumors demonstrating features suspicious for malignancy such as large tumor size (>10 cm) or radiographic evidence of adjacent organ or vascular invasion. Complete en bloc resection is paramount in the surgical approach to adrenocortical carcinoma; therefore, an incision is chosen that will maximize exposure of the adrenal mass while simultaneously allowing for resection of adjacent structures or caval thrombus, if necessary. For this purpose, a thoracoabdominal or transabdominal approach is preferred.
The patient is placed in the supine position. A subcostal incision is our preferred transabdominal approach with extension across the midline if further exposure is necessary. A midline incision is a fine alternative. The subcostal incision is made on the ipsilateral side of the tumor and extended to a chevron if wide exposure is necessary ( Fig. 32.1 ). The rectus abdominis and lateral abdominal musculature is divided. The superior epigastric vessels will be encountered posterior to the rectus abdominis.
Right adrenal resection begins with mobilization of the hepatic flexure of the colon and reflected inferiorly; the duodenum is reflected medially using the Kocher maneuver, exposing the IVC. Mobilization of the right lobe of the liver from the right triangular ligament and the falciform ligament allows for superior retraction of the liver. Liver retractors should be placed gently and padded to prevent capsular injury. The plane between the IVC and the adrenal mass is then developed in an attempt to isolate and ligate posteriorly inserting adrenal vein ( Fig. 32.2 ). After securely ligating and dividing the adrenal vein, the remainder of the adrenal mass can be dissected from their surrounding attachments. This is best accomplished by first dissecting the superior adrenal attachments and the accompanying vasculature. To minimize manipulation of the adrenal tumor, the kidney may be retracted inferiorly to expose the superior extent of the mass. Remember the open approach is reserved for tumors of known or suspected malignancy, and this can make for a very challenging dissection and adjacent organs (i.e., kidneys, liver) and the IVC should be resected en bloc with the adrenal mass, if involved.