Adrenal Myelolipoma
An adrenal myelolipoma is a benign, noncancerous tumor of the adrenal gland made up of mature fat mixed with bone marrow–like blood-forming tissue. It does not produce hormones and does not spread. Most adrenal myelolipomas are asymptomatic and are discovered incidentally on abdominal imaging. Their characteristic mixture of fat and soft tissue on CT and MRI often allows a confident diagnosis without biopsy. Larger tumors can occasionally cause pain, pressure symptoms, or bleeding, but the great majority require only reassurance and, in selected cases, periodic follow-up imaging.
What is it?
The adrenal glands are two small triangular organs that sit on top of the kidneys. They produce important hormones, including cortisol, aldosterone, and adrenaline. An adrenal myelolipoma is a benign tumor of the adrenal gland made up of mature fat and bone marrow–like tissue. It is not cancerous and does not spread. Myelolipomas are generally nonfunctioning, although some patients have a coexisting hormone-producing adrenal disorder that requires separate evaluation.
The exact cause of adrenal myelolipomas is not fully understood. They are thought to develop from progenitor cells within the adrenal gland that give rise to both fatty and blood-forming tissue. Adrenal myelolipomas may occur alongside other adrenal or endocrine conditions in some patients, including long-standing stress on the adrenal gland from chronic illness or hormonal conditions, but most occur sporadically without any identified underlying disease.
Adrenal myelolipomas most often affect one adrenal gland, although both can be involved in a minority of patients. Tumor size varies widely; many are only a few centimeters, while others can grow to be much larger. Larger tumors are more likely to produce symptoms or complications.
Most adrenal myelolipomas cause no symptoms and are discovered incidentally on abdominal imaging performed for unrelated reasons. When symptoms occur, they usually reflect the size or location of the tumor rather than any hormonal effect. Possible features include vague upper abdominal, flank, or back discomfort, a sense of fullness or pressure, and, less commonly, more significant pain. Very large tumors can occasionally displace nearby organs. Rarely, an adrenal myelolipoma can bleed spontaneously or after trauma, producing sudden severe pain and, in more extreme cases, signs of significant blood loss.
Adrenal myelolipomas are typically nonfunctional, meaning they do not produce hormones. However, a small number of patients have another coexisting adrenal condition—such as an adrenal adenoma, congenital adrenal hyperplasia, or Cushing syndrome—that is responsible for any hormonal symptoms. This is why hormonal evaluation is often considered when features are atypical, when tumors are large, or when symptoms suggest possible hormone excess.
Diagnosis is usually made confidently on imaging because of the characteristic mixture of fat and soft tissue within the tumor. CT of the abdomen typically shows a well-defined adrenal mass containing areas of very low density corresponding to mature fat, mixed with denser soft tissue representing the blood-forming component. MRI provides excellent tissue characterization and can further confirm the presence of fat within the tumor. Ultrasound may show a mass with characteristic features but is generally less useful than CT and MRI for detailed evaluation. In most cases, these imaging findings are sufficient for diagnosis, and biopsy is not needed. In rare situations in which imaging is atypical—such as tumors with very little visible fat, or lesions in which malignancy or another condition cannot be reliably excluded—additional testing may be considered.
Blood tests to assess adrenal hormone function are often obtained in patients with adrenal masses, particularly when tumors are large or when imaging findings are not fully characteristic. Tests may include morning cortisol and cortisol-related studies, plasma or urine metanephrines (to help exclude pheochromocytoma), aldosterone and renin levels, and dehydroepiandrosterone sulfate (DHEA-S). Exclusion of pheochromocytoma is particularly important before any planned biopsy or surgery, because manipulation of a pheochromocytoma can trigger a dangerous release of hormones.
Important to Know
For the great majority of patients with adrenal myelolipomas, no specific treatment is needed. Once the diagnosis is confidently established by imaging and, when appropriate, hormonal evaluation, most tumors can be managed with reassurance and clear documentation of the finding in the medical record. Many small, stable, characteristic myelolipomas do not require further follow-up beyond routine care, while larger or less typical lesions may be monitored with periodic imaging for a defined time to confirm stability.
Lifestyle changes are generally not needed for typical adrenal myelolipomas. Patients can usually maintain normal diet, exercise, and activity levels without restriction. There is no need to avoid specific foods solely because of an adrenal myelolipoma, although general healthy habits remain important for overall health. Patients with larger tumors may occasionally be advised to be cautious about high-impact activities that carry a meaningful risk of significant abdominal trauma, although such recommendations are individualized.
Treatment is considered in selected situations. These typically include adrenal myelolipomas that cause significant and persistent symptoms not explained by other conditions; very large tumors (thresholds vary, but tumors larger than about 7 to 10 centimeters are more likely to be considered for surgery); rapidly enlarging lesions; complications such as significant bleeding or rupture; lesions with atypical imaging features in which another diagnosis—including malignancy—cannot be reliably excluded; and cases in which a coexisting hormone-producing adrenal condition requires treatment. When surgery is indicated, adrenalectomy (removal of the affected adrenal gland) is typically performed, most often laparoscopically or through minimally invasive techniques by surgeons with adrenal experience. Adrenal-preserving approaches may be considered in selected cases, and decisions are individualized in collaboration with endocrine or hepatobiliary surgeons and endocrinologists.
Before any planned biopsy, aspiration, or surgical procedure involving the adrenal gland, appropriate hormonal evaluation—particularly exclusion of pheochromocytoma—is essential. Coordination with endocrinology helps ensure that appropriate testing and, when necessary, preoperative medications are used to minimize risk.
Patients who undergo unilateral adrenalectomy typically retain normal adrenal function through the remaining gland and do not require long-term hormone replacement. Care after surgery focuses on healing, monitoring for any complications, and confirming that adrenal function is preserved.
For patients with adrenal myelolipomas that are being observed, awareness of warning signs is important. Any new or worsening abdominal or flank pain, signs of significant bleeding, or acute symptoms warrant medical evaluation. Clear documentation of the diagnosis in the medical record helps ensure that the finding is not misinterpreted on future imaging and that appropriate consideration is given if new imaging or interventions are planned in the future.
Care is typically coordinated by primary care clinicians and, when relevant, radiologists, endocrinologists, and endocrine or hepatobiliary surgeons. Imaging and laboratory findings are interpreted alongside the patient’s symptoms, examination, and broader clinical context rather than in isolation.
Although a typical adrenal myelolipoma is almost always a benign and asymptomatic finding, any new abdominal symptoms should be evaluated based on their own clinical features rather than automatically attributed to a previously identified myelolipoma. Coexisting conditions—such as kidney disease, other abdominal disorders, or other adrenal conditions—can occur and should be considered independently.
Patient education plays an important role. Understanding that most adrenal myelolipomas are benign, nonfunctioning, and generally require no specific treatment can reduce anxiety while allowing appropriate follow-up when needed.
Red flag symptoms include sudden severe upper abdominal, flank, or back pain (especially after trauma to the abdomen), lightheadedness or fainting, rapid heart rate, cool clammy skin or signs of shock, severe vomiting with abdominal pain, sudden severe hypertension with headache or palpitations (which may suggest an underlying hormone-producing lesion), high fever with chills, or signs of severe infection. These warrant prompt or urgent medical evaluation, as they may indicate bleeding, rupture, an unrecognized hormone-producing tumor, or another serious condition.