Leiomyolipoma

Last revised by Arlene Campos on 12 Jan 2024

Leiomyolipomas are rare benign tumors of the uterus, similar to leiomyomas, except that they contain bulk fat.

Leiomyolipomas are typically found in postmenopausal women, on a background of additional leiomyomas 1.

The majority are asymptomatic and discovered incidentally. They may present with pelvic pain or palpable mass 1.

Leiomyomas are similar to leiomyomas histologically, containing smooth muscle cells, connective tissue, and fat. It is hypothesized that they may represent lipomatous degeneration of smooth muscle 1.

They are most commonly located intramurally within the body of the uterus, although can originate anywhere along the uterus (including the cervix) and also may be subserosal 2.

Leiomyolipomas slightly vary in appearance depending on their composition. They generally appear as benign uterine masses resembling fibroids, except that there is a component of bulk fat 1.

  • hyperechoic mass with hypoechoic periphery (thought to represent surrounding myometrium) 2
  • fatty component appears low-density, typically measuring between -40 to -100 HU 1
  • much of the lesion may resemble a leiomyoma - dark on T1/T2WI
  • evidence of macroscopic fat component should suggest the diagnosis 1:
    • a component with bright signal on T1WI
    • chemical shift artifact along frequency-encoding axis
    • loss of signal following fat suppression

Leiomyolipomas require no treatment 2. They are thought to undergo malignant degeneration, however extremely rarely 3.

The differential diagnosis for bulk fat-containing pelvic lesions (including both uterine and ovarian origin) includes:

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