Adrenal metastasis occurs when cancer cells from a tumor elsewhere in the body spread to one or both adrenal glands, the small hormone-producing organs that sit on top of the kidneys. The adrenals are among the most common destinations for metastatic cancer, likely because of their rich blood supply and a local microenvironment that seems to welcome tumor growth. Most adrenal metastases produce no symptoms at all and are discovered incidentally on imaging done for other reasons, which makes the diagnostic challenge less about detection and more about figuring out whether a newly spotted adrenal mass is actually cancer or just one of the harmless lumps that adrenal glands frequently develop on their own.
Which Cancers Spread to the Adrenal Glands
Almost any solid tumor can send metastases to the adrenals, but some do so far more often than others. In a large study from an academic medical center, renal cell carcinoma was the most common source by a wide margin, followed by lung adenocarcinoma, urothelial carcinoma, and hepatocellular carcinoma.1PubMed. Metastatic diseases to the adrenal gland: A comprehensive study from an academic institution with emphasis on clinical occult cases Melanoma, breast cancer, and colorectal cancer also frequently metastasize to the adrenals, though they were less dominant in that particular series. The takeaway for anyone with a known cancer and a new adrenal mass is that the risk depends heavily on the primary tumor type. A person with renal cell carcinoma and an enlarging adrenal nodule, for example, faces higher suspicion than someone whose primary cancer rarely travels there.
Why the adrenals attract metastatic cells at all is an area of active research. The glands receive a disproportionately high volume of arterial blood relative to their size, which gives circulating tumor cells plenty of opportunity to lodge there. Beyond simple blood flow, laboratory work has shown that interactions between cancer cells and the adrenal gland tissue can trigger changes in how those cells behave, making them stickier and more invasive.2PubMed. Prostate cancer metastasis: role of the host microenvironment in promoting epithelial to mesenchymal transition and increased bone and adrenal gland metastasis In effect, the adrenal microenvironment may not just passively receive cancer cells but actively help them take hold.
Why Most Adrenal Metastases Are Silent
The adrenal glands have a lot of functional reserve. Even when a tumor replaces a significant portion of one gland, the opposite gland can compensate and keep hormone output normal. This means the majority of adrenal metastases cause no symptoms that would alert you or your doctor. They turn up on CT scans or PET scans ordered for cancer staging or routine follow-up, appearing as an incidental finding that then has to be investigated.
When symptoms do occur, they typically point to either the mass itself or to hormone disruption. Large metastases, particularly those exceeding about 5 centimeters, can cause a recognizable pain syndrome: unilateral flank pain, sometimes with an abdominal component, reported most often in patients with lung cancer.3Journal of Pain and Symptom Management. A pain syndrome associated with large adrenal metastases in patients with lung cancer This pain can be mistaken for kidney problems or musculoskeletal issues, delaying the correct diagnosis. In patients treated with stereotactic radiation for painful adrenal metastases, pain improvement was consistently reported after treatment.4Advances in Radiation Oncology. Stereotactic body radiation therapy for adrenal gland metastases: Outcomes and toxicity
Adrenal Insufficiency From Bilateral Metastases
A common worry is that metastases will destroy enough adrenal tissue to cause adrenal insufficiency, a condition where the body can no longer produce adequate cortisol. This can happen, but it is rarer than many people assume. A systematic review and meta-analysis that applied strict criteria found that among patients with documented bilateral adrenal disease, only about 3% to 8% developed confirmed adrenal insufficiency.5Heliyon. Adrenal insufficiency due to bilateral adrenal metastases – A systematic review and meta-analysis The range depends on how the diagnosis is defined, but either way, the glands have to be very extensively replaced before hormone production fails. Still, for anyone with bilateral adrenal metastases, periodic screening with a morning cortisol level or a stimulation test is worthwhile, because adrenal insufficiency can be life-threatening if it goes unrecognized and untreated.
When adrenal insufficiency does develop, it is managed with daily glucocorticoid replacement. Current guidelines suggest roughly 15 to 25 milligrams of hydrocortisone per day in divided doses, though recent research on cortisol production rates suggests that the lower end of that range, around 15 milligrams, may be more physiologically appropriate for many patients.6PubMed Central. Daily Glucocorticoid Replacement Dose in Adrenal Insufficiency, a Mini Review Patients also need to learn “sick-day rules” for increasing the dose during illness or surgery, and they should carry an emergency injection kit and medical alert identification.
Telling a Metastasis Apart From a Harmless Adrenal Mass
This is arguably the most clinically important question surrounding adrenal metastases: when a scan shows something on the adrenal gland of a cancer patient, is it actually metastatic cancer, or is it one of the adrenal adenomas (benign fatty tumors) that are extremely common in the general population? The distinction matters enormously because it can change cancer staging and determine whether someone is a candidate for curative treatment or shifted to a palliative plan.
Imaging forms the backbone of the workup. The standard approach involves non-contrast CT to measure the mass’s density, contrast-enhanced CT with delayed washout analysis, and MRI with chemical shift sequences.7PubMed Central. Pitfalls and differential diagnosis on adrenal lesions: current concepts in CT/MR imaging: a narrative review Each technique exploits a different physical property. Non-contrast CT relies on the fact that benign adenomas are typically fat-rich and therefore appear low-density on the scan. A widely used threshold in oncologic patients is about 20 Hounsfield units: masses below this level are very likely benign, while those above it raise suspicion for metastasis.8Endocrinology and Metabolism. Radiographic Characteristics of Adrenal Masses in Oncologic Patients Size also matters. The same study found that a cutoff of about 22 millimeters separated suspicious from likely-benign masses with reasonable accuracy, though neither size nor density alone is conclusive.
Washout CT and Its Limits
Contrast-enhanced CT with washout analysis has long been a go-to method for indeterminate adrenal masses. The idea is that benign adenomas wash out contrast material faster than metastases. Traditional thresholds of 60% for absolute percentage washout and 40% for relative percentage washout have been widely taught, but real-world performance is less tidy than those numbers suggest. A study evaluating these thresholds in clinically challenging cases found that they misclassified roughly a third of masses in either direction.9PubMed Central. Adrenal wash-out CT: moderate diagnostic value in distinguishing benign from malignant adrenal masses Raising the cutoffs dramatically (to above 83% absolute washout) reduced false negatives for malignancy but correctly identified only about 11% of benign tumors. In other words, washout CT is useful as one piece of the puzzle but is not the slam-dunk diagnostic tool it is sometimes portrayed as.
MRI Chemical Shift Imaging
MRI offers a different angle. Chemical shift imaging detects the presence of intracellular fat, which adenomas contain in abundance and metastases typically do not. On chemical shift sequences, adenomas show a visible drop in signal between in-phase and out-of-phase images. One study found that moderate to significant signal loss was reliably seen in lipid-rich adenomas but never in metastases or other malignant masses.10PubMed Central. Comparative Analysis of FSE T2 Weighted, Chemical Shift and Dynamic Contrast-Enhanced MR Imaging in the Characterization of Adrenal Masses Based on Qualitative and Quantitative Parameters A separate study quantified this: using a standard threshold for the signal intensity index, the technique achieved sensitivity above 90% and specificity above 93% for distinguishing adenomas from metastases.11Journal of Computer Assisted Tomography. A Prospective Study on the Utility of Diffusion-Weighted and Quantitative Chemical-Shift Magnetic Resonance Imaging in the Distinction of Adrenal Adenomas and Metastases The main pitfall is lipid-poor adenomas, which lack enough intracellular fat to produce the expected signal drop and can therefore mimic metastases on MRI.
An additional complication arises when the primary cancer is clear cell renal cell carcinoma. Those metastases can themselves contain intracellular lipid, blurring the chemical shift results. One study specifically looking at this scenario found that while the signal intensity index was still significantly higher in adenomas than in renal cell carcinoma metastases, accuracy was lower than in the general population.12PubMed. Adrenal adenoma and metastasis from clear cell renal cell carcinoma: can they be differentiated using standard MR techniques? This is one of those cases where the imaging alone cannot give a confident answer, and additional tools become necessary.
PET-CT and Combined Approaches
PET-CT, which uses a radioactive glucose tracer to highlight metabolically active tissue, adds another layer. Metastatic lesions tend to consume more glucose than benign adenomas, so they light up brighter on the scan. The accuracy is generally good, and combining PET-CT with standard adrenal protocol CT pushes overall accuracy above 90%.13PubMed. The value of adding (18)F-FDG PET/CT to adrenal protocol CT for characterizing adrenal metastasis (≥ 10 mm) in oncologic patients A multicenter study found that PET-CT also performs well for adrenal masses from non-lung cancers, which is reassuring since much of the early data came from lung cancer populations.14Egyptian Journal of Radiology and Nuclear Medicine. The F-18 FDG PET/CT evaluation of the metastatic adrenal lesions of the non-lung cancer tumors compared with pathology results Multivariate models combining the primary cancer type, enhancement pattern, and pre-contrast density have achieved sensitivity above 90% and specificity around 74% for identifying metastases without any biopsy.15PubMed Central. Distinguishing between metastatic and benign adrenal masses in patients with extra-adrenal malignancies
When Biopsy Is Needed
If imaging remains inconclusive and the answer would genuinely change management, percutaneous biopsy offers a definitive tissue diagnosis. The procedure is performed under CT or ultrasound guidance and is the most common reason for adrenal biopsy overall: in one large series, over 80% of adrenal biopsies were done to evaluate suspected metastasis.16PubMed. Procedural and clinical outcomes of percutaneous adrenal biopsy in a high-risk population for adrenal malignancy Technical success rates are very high, with one recent study reporting success in nearly all cases (over 99%), and diagnostic accuracy above 97%.17PubMed. Percutaneous Adrenal Biopsies in Patients with Cancer: The Utility of Preprocedural Endocrine Workup Complications occur in roughly 4% to 9% of cases, mostly minor bleeding or transient blood pressure spikes, though rare serious hemorrhage can occur. The critical prerequisite before any adrenal biopsy is ruling out pheochromocytoma with biochemical testing, since puncturing an undiagnosed pheochromocytoma can trigger a dangerous hypertensive crisis.
Surgical Removal of Adrenal Metastases
For patients with an isolated or limited adrenal metastasis and a controlled primary tumor, surgical removal (adrenalectomy) is the most aggressive local treatment option and the one with the longest track record. The surgery is increasingly done laparoscopically or robotically, which shortens recovery compared with open approaches. A study comparing outcomes in patients who underwent surgical resection with those who did not found a striking difference: median survival was roughly 34 months in the surgery group versus about 6 months without surgery.18PubMed Central. Adrenalectomy may increase survival of patients with adrenal metastases That comparison is not a randomized trial, and patients selected for surgery are inherently healthier and have less widespread disease, so the true survival benefit is likely smaller. But the size of the difference, combined with consistent findings across multiple similar studies, supports surgery as a reasonable choice in well-selected patients with limited metastatic burden.
Stereotactic Body Radiation Therapy
When surgery is not feasible because of the patient’s general health, tumor location, or medical comorbidities, stereotactic body radiation therapy (SBRT) delivers high-dose, precisely targeted radiation in a small number of sessions, typically three to five. This has become a well-established alternative for adrenal metastases. In one series, the cumulative incidence of local failure was under 8% at one year and about 19% at three years, with no severe toxicity reported.19PubMed Central. Stereotactic body radiation therapy for adrenal gland metastases: Outcomes and toxicity The treatment did not meaningfully affect kidney function, an important consideration given the adrenal glands’ proximity to the kidneys.
A separate study reported an overall response rate of 86%, with nearly a third of patients achieving a complete response on imaging. Two-year local control exceeded 84%, and the treatment was well tolerated with only mild side effects.20PubMed Central. Stereotactic body radiotherapy (SBRT) for adrenal metastases of oligometastatic or oligoprogressive tumor patients A trend in that study suggested that higher biologically effective doses and smaller tumor volumes predicted better local control, which aligns with the general principle across radiation oncology that smaller targets do better with SBRT.
Percutaneous Ablation as a Third Local Option
Image-guided ablation, where a needle is placed through the skin into the tumor and energy (heat, cold, or chemical) destroys the cancer cells, offers yet another minimally invasive approach. Techniques include radiofrequency ablation, microwave ablation, and cryoablation. A meta-analysis pooling data from nearly a thousand patients found a one-year local control rate of 80% and a one-year overall survival rate of 77%.21PubMed. Image-Guided Percutaneous Ablation of Adrenal Metastases: A Meta-Analysis of Efficacy and Safety The rate of severe adverse events was about 16%, making it somewhat riskier than SBRT in terms of procedural complications, though the types of complications differ. The most concerning is hemorrhage or hypertensive crisis, the latter again related to the adrenal gland’s hormonal nature.
A single-institution study that treated patients with curative intent found even better numbers: local recurrence in under 9% of tumors and recurrence-free survival of 88% at three years, with a median overall survival of roughly 34 months.22PubMed. A single-institution experience in image-guided thermal ablation of adrenal gland metastases The difference between these results and the meta-analysis likely reflects patient selection: a specialized center treating carefully chosen patients with small tumors will outperform the broader population of studies.
The Immunotherapy Resistance Problem
Immune checkpoint inhibitors have transformed outcomes in melanoma, lung cancer, and several other tumor types over the past decade, but the adrenal gland appears to be a particularly tough nut for these drugs to crack. A study of melanoma patients found that adrenal metastases responded to checkpoint inhibitors at a rate of only 16%, compared with 22% for other metastatic sites in the same patients, and 55% in melanoma patients without any adrenal involvement at all. Patients with adrenal metastases also had substantially shorter survival.23Journal of the National Comprehensive Cancer Network. Melanoma Metastases to the Adrenal Gland Are Highly Resistant to Immune Checkpoint Inhibitors
This pattern is not limited to melanoma. A study of patients with microsatellite instability-high colorectal cancer, a tumor type that typically responds well to immunotherapy, found that the adrenal gland acted as a sanctuary site. While other metastatic locations responded to treatment, the adrenal gland was where disease eventually progressed in all five patients studied, with progression occurring even while other sites remained controlled.24Journal for ImmunoTherapy of Cancer. Adrenal gland as a sanctuary site for immunotherapy in patients with microsatellite instability-high metastatic colorectal cancer The explanation appears to involve the adrenal gland’s unique immune microenvironment. The glands naturally produce cortisol and other steroid hormones that suppress immune activity, and this local immunosuppressive milieu may shield tumor cells from the immune attack that checkpoint inhibitors are trying to unleash.25PubMed Central. The Immune Biology of the Adrenal Gland Microenvironment and Its Role in Metastatic Progression
This has practical consequences. When an adrenal metastasis is the only site not responding to immunotherapy, adding a local treatment like surgery, SBRT, or ablation to knock out the resistant spot while continuing systemic therapy is a strategy that oncologists increasingly consider. The evidence for this combined approach is still emerging, but the biological rationale is sound.
Molecular Differences Between Primary Tumors and Their Adrenal Metastases
Cancers evolve as they spread, and the metastasis that arrives in the adrenal gland may not be genetically identical to the original tumor. In a study of lung cancer patients with isolated adrenal metastases, mutations in the TP53 gene were found in about 61% of primary tumors but 85% of the corresponding adrenal metastases, and in a fifth of cases, the mutation patterns differed meaningfully between the two sites.26PubMed. Clinical Characteristics, Molecular Phenotyping, and Management of Isolated Adrenal Metastases From Lung Cancer These discrepancies matter because targeted therapies are chosen based on the tumor’s molecular profile. If you rely solely on the biopsy of the primary tumor, you might miss a targetable mutation that emerged in the metastasis, or try to target a mutation that the metastasis no longer carries. For patients with isolated adrenal metastases who are being considered for targeted therapy, molecular profiling of the adrenal lesion itself, not just the primary tumor, can influence treatment selection.
Renal Cell Carcinoma and the Adrenal Gland
Renal cell carcinoma deserves special mention because of the anatomical intimacy between the kidney and the adrenal gland. The ipsilateral adrenal gland sits right on top of the kidney, and in some cases, adrenal involvement represents direct local extension rather than distant metastatic spread. This distinction is more than academic: direct extension is staged differently and can sometimes be managed with a combined nephrectomy-adrenalectomy as part of a curative operation, while a distant adrenal metastasis to the opposite side implies stage IV disease.
Imaging algorithms for renal cell carcinoma patients with adrenal masses have been specifically studied. One investigation found that a model combining lymph node status, fat invasion, mass size, density, and the attenuation difference between the kidney tumor and the adrenal mass achieved near-perfect diagnostic accuracy, with sensitivity at 100% and specificity above 92% in distinguishing metastases from incidental adenomas.27PubMed. Differentiation of Benign From Metastatic Adrenal Masses in Patients With Renal Cell Carcinoma on Contrast-Enhanced CT When the adrenal mass on imaging closely matches the kidney tumor in density and there are other signs of aggressive disease, suspicion should be high. When the adrenal mass is small, low-density, and the kidney cancer is otherwise early-stage, an adenoma is far more likely.