Definition: Rare benign tumor consisting of macroscopic fat interspersed with hematopoietic elements

Appearance varies depending on admixture of fatty and myeloid soft tissue components

Predominantly fatty: Well-defined, homogeneous, hyperechoic suprarenal mass

• ○
  

  When small, difficult to distinguish from echogenic retroperitoneal fat

When myeloid cells predominate: Heterogeneous mass, isoechoic or hypoechoic

Punctate calcification in 25-30% of cases

Hemorrhage more common when > 4 cm, varied appearance

Color Doppler: Avascular to hypovascular

Adrenal hemorrhage

Pheochromocytoma

Liposarcoma

Renal angiomyolipoma

Adrenal adenoma

Adrenal metastases

Contains mature fat cells with variable mixture of myeloid cells, erythroid cells, and megakaryocytes

Usually in older age group: 50-70 years; M=F

Usually found incidentally

Clinical signs are usually absent except in rare cases of hemorrhage and rupture producing acute abdomen

Pain from necrosis, hemorrhage, or compression of structures

Confirm that fat-containing lesion arises from adrenal gland and not adjacent organs or retroperitoneum

Adrenal mass with discrete focus of macroscopic fat is virtually diagnostic of myelolipoma

Look for acoustic shadowing or propagation speed artifact from fat