Epithelioid angiomyolipoma of kidney

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Epithelioid angiomyolipomas (EAML) are rare variants of the more common renal angiomyolipoma. They have malignant potential.

Pathology

Like more common renal angiomyolipomas, EAMLs are considered perivascular epithelioid cell tumors (PEComas). EAMLs were regarded as a separate renal mass entity by the WHO in 2016.

Radiographic features

Epithelioid angiomyolipomas do not have a specific appearance. Some features that have been associated with them:

CT
  • hyper-attenuating mass with variable enhancement
MRI
  • T2: hypointense
  • IP/OOP imaging: signal dropout of microscopic fat content on OOP
  • DWI/ADC: hyperintense on DWI
  • T1 C+: marked hypervascularity with rapid washout

Differential diagnosis

The imaging appearance is similar to renal cell carcinoma and AML with minimal fat.

The diagnosis can be considered if a renal mass has small foci of macroscopic fat without calcification, which would be atypical for renal cell carcinoma. Renal biopsy would be needed for confirmation, however.