Introduction:
An adrenal incidentaloma is a mass lesion of size bigger than one centimeter in length. It may be accidentally found in a radiographic examination. Mostly adrenal incidentaloma is a benign adenoma; their increasing prevalence provides challenges in diagnosis and therapeutically. The adrenal incidentaloma diagnosis is made to determine whether this tumor should be removed surgically. The prevalence of the mass of the adrenal gland in CT of the abdomen is between 0.6 percent and 1.3 percent. The prevalence of adrenal mass in CT of the thoracic abdomen and pelvis is between 0.4 percent and 4.4 percent. The prevalence of adrenal mass in autopsy in patients with no adrenal disease history is 1.4 percent and 9 percent.
What Are the Differential Diagnosis of Adrenal Incidentalomas?
The differential diagnosis of adrenal mass includes adenoma, myelolipoma, lipoma, cyst, pheochromocytoma, adrenal cancer, hyperplasia, metastatic cancer, and tuberculosis. Some adenoma is benign but hyperfunctioning, thus needing more evaluation. Myelolipoma, cyst, and lipoma are characteristics of CT scans. Pheochromocytomas become clear on taking a patient history or by examining clinically. The most demanding diagnosis is an adenoma or metastatic cancer because it looks like a small adrenal mass. (small adenomas).
What Are the Imaging Studies Done for Adrenal Incidentalomas?
Assessment of the adrenal gland's mass usually begins with different imaging techniques. Fine needle aspiration biopsy (FNA) and cytology are also obtainable. Also, adrenal masses that are detached can be evaluated biochemically. Adrenal vein sampling is also rarely used. The most commonly and effectively used imaging techniques for diagnosing adrenal mass are non-contrast CT, MRI, and adrenal Scintigraphy.
- Noncontrast CT (Computed Tomography Scan) - A CT scan can detect adrenal bleeding, cysts, and myelolipomas. They have features of non-contrast CT scans that do not look like cancer or malignant lesions; thus, their diagnosis can be eliminated. In diagnosis, if the cyst is non-symptomatic, there is no pain, or if it is not a large myelolipoma, non-surgical treatment is planned. Benign adenomas are discrete masses with smooth, even homogeneous encapsulated borders. Malignant adrenal lesions look different from benign adenomas, but until they become larger, it is hard to find the difference. Adrenal carcinomas are malignant and inhomogeneous, have an irregular border, are locally invasive, and have lymphadenopathy in adjacent areas. Now also, studies are done to differentiate adenomas from carcinomas by radiologists. One of the methods is the Hounsfield unit. In this method density or mass of the lesion found in the CT scan is compared with the density of water. And it is assigned to the value of 0 Hounsfield units. Adenomas have low values that are less than or equal to ten. a CT scan cannot differentiate between whether the lesion is benign or malignant and whether the lesion is non-functional or hyperfunction. Malignant lesions are normally more than 18 units. A small percentage of benign lesions are misdiagnosed as malignant.
- MRI (Magnetic Resonance Imaging) - It is a good method of diagnosing adrenal masses, and one of its benefits is that it exposes the patient to less ionizing radiation. But MRI, its higher cost than CT, is one of its drawbacks. Adenomas' low signal on T2 weighted images is used in the pathology of the adrenal gland. Pheochromocytomas are seen on T2 weighted sequences. To find between benign and malignant lesions, chemical shift MRIs are used. The benign lesion has more content lipids and shows a dropping of intensity signal, which darkens on chemical shift. The cancerous lesion shows no loss of signal intensity. Detection of signal loss on opposed phase images was more accurate in adrenal masses.
- Adrenal Scintigraphy - It is a method of discriminating between benign and malignant lesions. There are two types of scintigraphy-metaiodobenzylguanidine(MIBG) Scintigraphy and 1-6-beta-iodomethyl-norcholesterol (NP-59) Scintigraphy. MIBG is used in pheochromocytoma. The decarboxylation tumor has extra vesicles, which will take enough MIBG to create an image on Scintigraphy. It is used for the detection of recurrent tumors. It also helps to find extra-adrenal disease or whether it is functioning. The disadvantage of MIBG is its cost, high level of radiation, and limited availability. In NP-59, it is not possible to differentiate between benign and malignant masses.
- FNA Biopsy, Adrenal Vein Sampling, and Biochemical Testing - FNA biopsy is done to find extra-adrenal malignancy when tissue diagnosis is required to find a diagnosis in metastasis. Adrenal vein sampling is rarely done as it causes hemorrhage, pancreatitis, and pneumothorax. It is done to find idiopathic hyperaldosteronism. After the detection of adrenal mass, certain biochemical tests are done to distinguish if it is active biochemically or not.
What Is Aldosteronoma?
Overactive adrenal adenoma is aldosterone producing tumor or aldosteronoma. It is the main cause of hyperaldosteronism. It is a disease of hypertension and hypokalemia. It has a speckled appearance, is well encapsulated, small, and mimics benign. To find this condition plasma aldosterone to plasma renin ratio is calculated, and if it is more than 20mg/ml/ hr, then this condition is suspected.
What Is Cortisol-Producing Adenoma?
This is the second type of function of the adrenal tumor. Cushing syndrome occurs in hypercortisolism, including hypertension, obesity, easy disability, and diabetes. Low dose dexamethasone suppression test is done to screen if the patient has an adrenal mass. If the patient has positive for the Dexamethasone suppression test and low adrenocorticotropic hormone means the disease of suppression of cortisol is adrenal based, not based on pituitary
What Is Pheochromocytoma?
It is a functioning adenoma; symptoms include hypertension with palpitation, headache, sweating, anxiety, pallor, and tremor. Altered levels of plasma catecholamines are a diagnostic feature of pheochromocytoma. A Clonidine suppression test is also used for diagnosis.
What Is Adrenocortical Carcinoma?
This is a rare condition. It occurs in one in 1.7 million. They are large masses with irregular borders found on CT scans. These masses are diagnosed based on their size. When they are found, they are 12 cm in diameter. A mass of more than 6 cm is removed. If the carcinoma is not detected in a CT scan, then the dehydroepiandrosterone sulfate level should be found.
What Is Adrenal Metastasis?
Metastasis is the second cause of adrenal incidentaloma. Primary tumors can metastasize into the breast and lungs as renal cell carcinoma, multiple myeloma, and lymphoma. Examination radiographically is done, an FNA biopsy is done to confirm metastasis in a mass, and a hyperfunctioning adrenal mass of any size should be removed.
What Is the Treatment Done for Adrenal Incidentalomas?
Functional adrenal incidentalomas must be removed surgically. For patients with non-functional tumors, the risk of adrenocortical cancer based on size and imaging characteristics will determine if they should be removed. Tumors that appear suspicious of cancer on imaging should be removed. Adrenalectomy, or the surgical removal of the adrenal gland, can be done in severe cases. However, the doctor will decide whether one or both adrenal glands need to be removed based on the imaging tests. People with inherited adrenal incidentalomas might require genetic counseling. The masses more than 4 cm in diameter must be definitely removed to avoid complications.
Conclusion
Accidental detection of adrenal mass is common nowadays with diverse imaging techniques. Each noticed mass should be assessed by radiographic testing and biochemical testing. No intervention is required if a mass of dimensions is less than three centimeters and is not developing in a three-month to one-year follow-up. But if mass dimensions increase in one year, then adrenalectomy is accomplished. Instantaneous adrenalectomy did for the over-functioning mass of any dimensions or non-functioning mass of more than four centimeters.
