Adrenal Myelolipoma
Key facts
- benign tumor incidentally discovered on CT usually in older patients
- present in 0.2-0.4% of patients based on autopsy series
- are never functioning and do not secret any hormones
- case reports show that tumors can spontaneously bleed or become necrotic. If they bleed can present symptomatically
- key is to recognize the benign nature of these lesions and avoid unnecessary workup for an incidental adrenal mass
CT Findings
- most tumors are simply large fatty masses while other tumors have a variable amount of fat visible.
- if no fat is present you can not make the diagnosis on CT
- foci of calcification not uncommon
- although most tumors are 2-4 cm in size others can be 10 cm or greater (20 cm masses have been reported)
MR Findings
- findings will vary depending on the amount of fat present but typically are hyperintense on T1-weighted images
Ultrasound
- echogenic mass in the adrenal bed
- if extensive fat component to tumor then hard to distinguish from the retroperitoneal fat
Pathology
- tumor composed of bone marrow elements including myeloid and erythroid cells and fatty elements.
- composed of variable amounts of mature adipose tissue
Clinical presentation
- usually as an incidental finding
- may present with an acute abdomen due to spontaneous hemorrhage (rare)
Differential Diagnosis
- adenoma- usually of low CT attenuation but not as much visible fat as a myelolipoma
- retroperitoneal liposarcoma- tumors may grow up to adrenal space and simulate a Myelolipoma especially if findings detected on a chest CT where the entire mass is not scanned
- renal angiomyolipoma- projected off superior pole of kidney can simulate a myelolipoma
- adrenal cyst- cysts are water density and do not contain fat
- metastases- metastases are of higher CT attenuation
References
- Adrenal Myelolipoma
Cyran KM, KenneyPJ, Memel DS et al.
AJR 1996;166:395 - The natural history and treatment of Adrenal Myelolipoma
Han M, BurnettAL, Fishman EK et al
J Urol 1997;157:1213 - Characterization of Adrenal Masses Using MR Imaging with Histopathologic Correlation
Heinz-Peer G, Honigschnabl S, Schneider B et al.
AJR 1999;173: 15-22