Diagnostic Ultrasound - Abdomen and Pelvis

Myelolipoma
Diagnoses: Adrenal Gland
TERMINOLOGY
• Definition: Rare benign tumor consisting of macroscopic fat
interspersed with hematopoietic elements
IMAGING
• Appearance varies depending on admixture of fatty and
soft tissue components
• US typically shows homogeneously hyperechoic mass, but it
may be heterogeneous iso- or hypoechoic
• CT typically shows well-defined, heterogeneous mass with
macroscopic fat that is diagnostic
• MR characterizes intratumoral fat best on fat-suppressed
sequences
TOP DIFFERENTIAL DIAGNOSES
• Adrenal hemorrhage
• Pheochromocytoma
• Liposarcoma
• Renal angiomyolipoma
KEY FACTS
• Adrenal adenoma
• Adrenal metastases
PATHOLOGY
• Contains mature fat cells with variable mixture of myeloid
cells, erythroid cells, and megakaryocytes
CLINICAL ISSUES
• Usually found incidentally
• Clinical signs are usually absent except in rare cases of
hemorrhage and rupture
DIAGNOSTIC CHECKLIST
• 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
(Left) Longitudinal ultrasound
of a myelolipoma shows a
lobulated, well-defined,
heterogeneously hyperechoic
mass ſt above the right
kidney . (Right) Coronal CT
demonstrates a
heterogeneous, encapsulated,
suprarenal mass
containing ill-defined, "smoky"
soft tissue elements ſt and
macroscopic fat st.
(Left) Axial T1 MR shows an
encapsulated, unilateral, left
adrenal mass containing
heterogeneous components.
Central soft tissue shows
central T1 hypointensity ſt,
while peripheral intratumoral
fat shows T1 hyperintensity
st. Note the normalappearing
right adrenal gland
. (Right) Axial T1 MR with
fat saturation shows signal
drop of the retroperitoneal fat
and in the peripheral
components of the mass st,
confirming the presence of
intratumoral fat. Note the
normal-appearing right
adrenal gland .
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