Tumors of the adrenal gland: findings on CT and MR imaging

A nationwide survey of adrenal incidentalomas in Japan: the first report of clinical and epidemiological features

The aim of this study was to reveal clear epidemiologic and clinical characteristics of incidentally discovered adrenal masses, termed adrenal incidentalomas (AIs), and to establish appropriate managemental and therapeutic regimens in Japan. This study had been originally carried out as a project of a research proposed on behalf of the Japanese Ministry of Health, Labour and Welfare, from 1999 to 2004. This nationwide multicenter study on AIs included 3,672 cases with clinically diagnosed AIs, involving 1,874 males and 1,738 females, with mean age 58.1 ± 13.0 years (mean ± SD). In the present study, we focused on the investigation of the real prevalence of various adrenal disorders with AI. The mean nodule size of AI based on computed tomography was 3.0 ± 2.0 cm. Compared to non-functioning adenomas (NFAs), tumor diameters were significantly larger in adrenocortical carcinomas (ACCs), pheochromocytomas, cortisol-producing adenomas (CPAs), myelolipomas, metastatic tumors, cysts, and ganglioneuromas (p < 0.01). Endocrinological evaluations demonstrated that 50.8% of total AIs were non-functioning adenomas, while 10.5%, including 3.6% with subclinical Cushing's syndrome, were reported as CPAs, 8.5% as pheochromocytomas, and 5.1% as aldosterone-producing adenomas. ACCs were accounted for 1.4% (50 cases) among our series of AIs. In conclusion, while almost 50 % of AIs are non-functional adenomas, we must be particularly careful as AIs include pheochromocytomas or adrenal carcinomas, because they may be asymptomatic. To our knowledge, this is the first and the largest investigation of AI, thus providing basic information for the establishment of clinical guidelines for the management of AI.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Practical Approach to Adrenal Imaging

Various pathologies can affect the adrenal gland. Noninvasive cross-sectional imaging is used for evaluating adrenal masses. Accurate diagnosis of adrenal lesions is critical, especially in cancer patients; the presence of adrenal metastasis changes prognosis and treatment. Characterization of adrenal lesions predominantly relies on morphologic and physiologic features to enable correct diagnosis and management. Key diagnostic features to differentiate benign and malignant adrenal lesions include presence/absence of intracytoplasmic lipid, fat cells, hemorrhage, calcification, or necrosis and locoregional and distant disease; enhancement pattern and washout values; and lesion size and stability. This article reviews a spectrum of adrenal pathologies.

Computed tomography and magnetic resonance images of adrenocortical oncocytoma cases

We present two cases of adrenocortical oncocytomas that were well-delineated on multi-detector computed tomography and magnetic resonance imaging. The images showed a well-enhanced large mass with multiple stippled calcifications in a 10-yr-old girl who was consulted due to precocious puberty. A well-enhanced solid mass with necrotic components was incidentally noticed in a 54-yr-old man. These lesions were resected and diagnosed as adrenocortical oncocytomas through immunohistochemical studies and electron microscopy. Adrenocortical oncocytomas are rare disease entities, therefore, we report these interesting, rare adrenocortical oncocytomas here with radiologic findings, and discuss differential diagnosis.

Giant adrenal myelolipoma associated with 21-hydroxylase deficiency: unusual association mimicking an androgen-secreting adrenocortical carcinoma

The objective of this study was to describe a case of giant myelolipoma associated with undiagnosed congenital adrenal hyperplasia (CAH) due to 21-hydroxylase (21OH) deficiency. Five seven year-old male patient referred with abdominal ultrasound revealing a left adrenal mass. Biochemical investigation revealed hyperandrogenism and imaging exams characterized a large heterogeneous left adrenal mass with interweaving free fat tissue, compatible with the diagnosis of myelolipoma, and a 1.5 cm nodule in the right adrenal gland. Biochemical correlation has brought concerns about differential diagnosis with adrenocortical carcinoma, and surgical excision of the left adrenal mass was indicated. Anatomopathologic findings revealed a myelolipoma and multinodular hyperplasic adrenocortex. Further investigation resulted in the diagnosis of CAH due to 21OH deficiency. Concluded that CAH has been shown to be associated with adrenocortical tumors. Although rare, myelolipoma associated with CAH should be included in the differential diagnosis of adrenal gland masses. Moreover, CAH should always be ruled out in incidentally detected adrenal masses to avoid unnecessary surgical procedures.

Uncommon adrenal masses: CT and MRI features with histopathologic correlation

Adrenal glands are common sites of diseases. With dramatically increased use of computed tomography (CT) and magnetic resonance (MR) imaging, more and more uncommon adrenal masses have been detected incidentally at abdominal examinations performed for other purposes. In this article, uncommon adrenal masses are classified as cystic masses (endothelial cysts, epithelial cysts, parasitic cysts, and pseudocysts), solid masses (ganglioneuroma, ganglioneuroblastoma, extramedullary plasmacytoma (EMP), neurilemmoma, and lymphoma), fat-containing masses (myelolipoma, teratoma), and infectious masses (tuberculoma), and the imaging features of these uncommon masses are demonstrated. Although most of these lesions do not have specific imaging features, some fat-containing masses and cystic lesions present with characteristic appearances, such as myelolipoma, teratoma, and hydatid. Combination with histopathologic characteristic of these uncommon masses of adrenal gland, radiological features of these lesions on CT and MR imaging can be accurately understood with more confidences. Moreover, CT and MRI are highly accurate in localization of uncommon adrenal masses, and useful to guide surgical treatments.

Adrenocortical carcinoma: contrast washout characteristics on CT

OBJECTIVE

The purpose of this study was to characterize pathologically proven adrenocortical carcinoma by examination of washout attenuation characteristics on contrast-enhanced CT images.

CONCLUSION

Adrenocortical carcinoma has relative contrast retention on delayed contrast-enhanced CT. All tumors in this series had a relative percentage washout less than 40%, a finding consistent with malignant disease.

Adrenal masses: mr imaging features with pathologic correlation

The detection of adrenal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance (MR) imaging is often useful for characterizing adrenal masses. Adrenal masses can be classified into various groups on the basis of the presence of intracellular lipid, macroscopic fat, hemorrhage, and cystic changes and the vascularity and shape of the tumor. These imaging features can be used by the radiologist to suggest or confirm a diagnosis for most adrenal masses, including adenoma, hyperplasia, simple and complicated cysts, lymphangioma, myelolipoma, pheochromocytoma, hemorrhage, cortical carcinoma, neuroblastoma, lymphoma, and metastases. Adenomas and metastases are common, and a decrease in signal intensity on out-of-phase images can be used to differentiate between them. Carcinoma is a possible diagnosis if that decrease in signal intensity is heterogeneous. Benign disease is diagnosed if macroscopic fat or a homogeneous cystlike lesion is seen. Recognition of the typical MR imaging features is important because it often changes the treatment approach and may obviate surgery.

Does tumor heterogeneity limit the use of the Weiss criteria in the evaluation of adrenocortical tumors?

Adrenal incidentalomas are detected more frequently with high-resolution imaging modalities. It is difficult to distinguish between benign and malignant lesions despite the so-called histologic Weiss criteria, imaging features, and molecular studies. We here present a 52 yr-old man who was found to have an adrenal incidentaloma during an annual check-up at his urologist. An 8 cm large adrenal lesion was detected on ultrasound, computed tomography, and magnetic resonance imaging with imaging features suggestive of malignancy. The lesion was hormonally inactive. A left-sided adrenalectomy was performed and histologic grading revealed a Weiss score of 2, suggesting a benign tumor. However, on further follow-up, the patient developed a local recurrence and pulmonary metastases diagnosed 6 yr after initial presentation. After repeat surgery in the left adrenal bed adrenocortical tumor tissue had a Weiss score of 8, clearly suggesting histologic malignancy. The patient received adjuvant mitotane therapy. Under this therapy, he developed a right-sided adrenal mass (contralateral from the primary tumor) of 2 cm size which disappeared during the following 9 months, whereas the pulmonary metastases remained unchanged, suggesting tumor clones with a variable response to treatment or spontaneous apoptosis. This case suggests that adrenal incidentalomas larger than 6 cm with imaging features such as intratumoral necrosis suggestive of malignancy, should be managed as potential cancers independent of the so-called Weiss criteria. In such patients, close follow-up examinations including high-resolution imaging (preferably 3 monthly) are needed and should be carried out by a physician familiar/specialized in endocrine oncology.

Lung cancer: value of various imaging modalities

Bronchogenic carcinoma is the leading cause of cancer death, and the overall prognosis remains poor. Imaging plays a critical role in the initial staging and follow-up of the disease. Bronchogenic carcinoma is typically detected first on chest radiography but computed tomography (CT) scan is the most important imaging technique, providing both staging information and assessment of recurrence. Magnetic resonance imaging (MRI) is most useful as a problem-solving tool. The increasing role of positron emission tomography (PET) scan in the evaluation is reviewed, and imaging guidelines of two national organizations are presented.

Adrenocortical oncocytoma

We report the case of an adrenocortical oncocytoma of the left adrenal cortex in a young woman. Physical examination revealed a mass in the left upper quadrant of the abdomen using abdomen ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI), which allowed the identification of a large and inhomogeneous mass between the left kidney and the spleen. The lesion was not endowed of any specific radiologic characteristic nor bysided by any biochemical activity that could allow a radiological presurgical diagnosis. Surgical resection led to the diagnosis of adrenocortical oncocytoma, with no aspects revealing malignant potential.

Imaging of adrenal masses

Adrenal pathology may be discussed based on hormonal functionality of the adrenals, appearances on imaging modality, or pathological determination. There are three main categories of adrenal function. Hyperfunctional states include Conn's or Cushing's syndrome. Lesions with normal function may be detected incidentally. Hypofunctional states may occur from idiopathic Addison's disease or some bilateral adrenal pathology. The most common modalities for characterization of adrenal pathology are non-enhanced CT, often followed by contrast CT or chemical shift MRI. The common appearance on non-enhanced CT is a well-defined homogeneous lesion with low-density due to the microscopic fat present and adrenal adenomas. When density criteria are not met, many of these may be characterized as adenomas by washed out of contrast or signal decrease using in phase and out-of-phase MRI sequences. Other non-invasive modalities may incidentally discover adrenal lesions, but are not typically used in the work-up. NP-59 is an uncommonly used nuclear medicine technique which is very specific for adenoma when correlated with pathology on other imaging studies. In the rare cases where non-invasive imaging is non-specific, fine needle aspiration or core biopsies may be necessary. However, biopsies have associated risks including infection and hemorrhage. The imaging appearance of an adrenal lesion is often specific such that further imaging is not necessary. These lesions include adrenal adenoma, pheochromocytoma, myelolipoma, adrenal cyst, and some large adrenocortical carcinomas. However, the findings in lesions such as metastasis, smaller primary adrenal carcinomas, lymphoma, granulomatous disease, and many adenomas are not as specific. In the proper clinical situation, follow-up imaging may be necessary, or biopsy may be warranted.

The diagnostic dilemma of incidentalomas. Working through uncertainty

The clinical evaluation of incidentally found nodules in the adrenal, thyroid, and pituitary glands is a challenge for physicians, regardless of their level of expertise. Choosing the most direct and cost-effective diagnostic approach and deciding when to treat or not to treat are common dilemmas in clinical practice. This article outlines one diagnostic approach using medical decision-making techniques such as heuristic thinking, critical appraisal of the literature, treatment threshold probability assessment, Bayes' theorem, and discriminant properties of diagnostic tests. These skills are usually discussed in postgraduate training curricula. Nevertheless, they often seem foreign to many clinicians. Evidence suggests that training in these techniques can improve clinical decision making. Use of the skills outlined herein provides a framework to work through the diagnostic uncertainty common in the evaluation of incidentalomas. This approach does not provide perfect answers, as noted in examplar 3 in which two experts argued about the actual pretest probability and treatment thresholds for pituitary incidentalomas. Even if there were no such disagreement, each patient presents unique issues, and there will always be some uncertainty. Nevertheless, this approach provides a starting point from which critical decisions can be made for individual patients.

Diagnosis of adrenal adenoma: value of central spot of high-intensity hyperintense rim sign and homogeneous isointensity to liver on gadolinium-enhanced fat-suppressed spin-echo MR images

Eighty-nine patients with 108 adrenal masses, either adenomas (n = 88) or malignant lesions (n = 20), underwent magnetic resonance imaging (MRI) of the abdomen at 0.5 T for the purpose of determining whether adrenal adenomas could be differentiated from malignant lesions on gadolinium-enhanced fat-suppressed T1-weighted spin-echo (SE) images (Gd-E FS T1WI) and on T2-weighted SE images. The imaging protocol included conventional unenhanced SE T1- and T2-weighted sequences and Gd-E FS T1WI. Three observers independently evaluated signal intensity on unenhanced and enhanced images and also the presence of structures of high signal intensity in the outer margin [hyperintense rim sign (HRS)] or in the center [hyperintense central spot (HCS)] of the adrenal masses. Forty-one (46.5%) of 88 adenomas were homogeneously isointense to liver in unenhanced and enhanced T1-weighted sequences and in T2WI. HCS and HRS were observed in 33/88 (37.5%) and 15/88 (17%) adenomas, respectively, on Gd-E FS T1WI; in contrast, these signs were never revealed in any case of malignant lesions. Sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy in classifying lesions as suggestive of adenoma were 93%, 90%, 98%, 75%, and 93%, respectively. Visual evaluation of details of tumor structures on Gd-E FS T1WI allows good characterization of adrenal masses. HCS, HRS, and homogeneous isointensity to liver are characteristic signs of adrenal adenomas.

Incidentally discovered adrenal masses: evaluation with gadolinium enhancement and fat-suppressed MR imaging at 0.5 T

The purpose of the study is to evaluate the ability of Gd-enhancement and fat-suppressed MR imaging operating at midfield strength to characterize incidentally discovered adrenal masses. Sixty patients with 72 adrenal masses incidentally discovered during US or CT exams were studied with a 0.51 MR unit following clinical and laboratory evaluation. After Gd-DTPA intravenous administration a modified three-point Dixon technique was performed in all patients. This technique provided three images sets: conventional T1-weighted SE images, fat-suppressed T1-weighted images and water-suppressed T1-weighted images. Diagnosis was established by means of surgery (11 lesions), fine-needle biopsy (21 lesions) and stability on ultrasonographic follow-up for at least 1 year (range, 12-87 months) from adrenal lesion discovery (40 masses). In most of adenomas (n = 55) an homogeneous enhancement was observed on postcontrast T1WI; however, 15 out of these lesions showed a small focal spot of high intensity in Gd-enhanced fat-suppressed images. On the contrary, malignant conditions (n = 6) and pheochromocytoma (n = 1), all had inhomogeneous signal intensities which were relatively higher after Gadolinium injection as compared with the liver. The fat suppression technique demonstrated areas of bright signal intensity related to high vascularity. The performance of three observers in order to differentiate malignant from benign conditions showed sensitivity, specificity, diagnostic accuracy, positive and negative predictive values of 100, 88.5, 90, 50 and 100% on the basis of gadolinium enhancement only, by utilizing the Dixon technique. In conclusion, although Gd-enhancement and fat-suppressed sequence helped correctly differentiate among the groups of incidentally discovered adrenal masses, the degree of overlap suggests that it is still difficult to characterize individual patients. However, the modified three-point Dixon technique after contrast material administration appears to be a further capability of midfield MRI in the characterization of adrenal tissue.

Incidentalomas. A disease of modern technology

The optimal strategy for hormonal screening of a patient with any incidentally discovered adrenal or pituitary mass is unknown. Our review of the endocrinologic literature supports the view that such patients are at slightly increased risk for morbidity and mortality. There is a benefit of early diagnosis for at least for some of the disorders, suggesting the importance of case finding. The data in Tables 1 and 4 illustrate that clinically diagnosed hormone-secreting adrenal and pituitary tumors are far less common than incidentalomas. From a clinical perspective, our ability to determine accurately those at increased risk among the vast majority who are not at increased risk is poor. Given the limitations of diagnostic tests, effective hormonal screening requires a sufficiently high pretest probability to limit the number of false-positive results. This condition is met to varying degrees in the patient with an adrenal mass or small incidentally discovered pituitary mass but no signs or symptoms of hormone excess. Even the more common lesions such as pheochromocytoma and prolactinoma are relatively rare. Subjecting patients to unnecessary testing and treatment carries its own set of risks. Initial costs aside, testing may result in further expense and harm as false-positive results are pursued, producing the cascade effect described by Mold and Stein as a "chain of events (which) tends to proceed with increasing momentum, so that the further it progresses the more difficult it is to stop." The extensive evaluations performed in some patients with incidentally discovered masses may reflect the unwillingness of many physicians to accept uncertainty, even in the case of extremely unlikely diagnoses. This unwillingness may be driven, in part, by fear of potential malpractice liability, the failure to appreciate the influence of prevalence data on the interpretation of diagnostic testing, or other factors. Indeed, the major justification for further evaluation of these patients is not so much to avoid morbidity and mortality for rate patients who truly are at increased risk but rather to reassure those in whom further testing is negative (and to reassure ourselves). Physicians must take care not to create inappropriate anxiety in patients by overemphasizing the importance of an incidental finding unless it is associated with a realistic clinical risk. Our recommendations utilize currently available information to minimize the untoward effects of the cascade. As evidence accumulates, recommendations may need to be revised. The benefit of diagnosis of one of these adrenal or pituitary disorders must be considered in the context of the patient's overall condition. Studies are needed to analyze the utility in clinical practice of hormonal screening for these common radiologic findings. We need to use these studies to identify the critical gaps in our knowledge and to adopt the epidemiologic methods of evaluation of evidence that have been applied to preventive measures. We must be careful to recognize lead-time bias in which survival can seem to be lengthened when screening simply advances the time of diagnosis, lengthening the period of time between diagnosis and death without any true prolongation of life. Length bias refers to the tendency of screening to detect a disproportionate number of cases of slowly progressive disease and to miss aggressive cases that, by virtue of rapid progression, are present in the population only briefly. Endocrinologists must avoid the pitfalls of overestimation of disease prevalence and of the benefits of therapy resulting from advances in diagnostic imaging. Clinical judgment based on the best available evidence should be complemented and not replaced by laboratory data.