Lipoleiomyom des Uterus

Uterine lipoleiomyomas result from degeneration of smooth muscle cells in an ordinary leiomyoma and represent a rare benign tumor of the uterus .

Epidemiology

Lipoleiomyomas have a reported incidence of 0.03-0.20% and are typically found in postmenopausal patients with typical uterine leiomyomas .

Clinical presentation

Although most patients are asymptomatic, they can present with symptoms similar to leiomyomas of the same size and location. Symptoms include, but are not limited to, abdominal/pelvic pain, palpable mass, and menstrual abnormalities.

Pathology

Many considered a uterine lipoleiomyoma as a distinct variety of leiomyoma. Histologically, it is composed of variable amounts of adipocytes and smooth muscle cells, separated by thin fibrous tissue. The exact etiology is not well known but is thought to represent fatty metaplasia of the smooth muscle cells of a leiomyoma. Lesions can vary in size from a few mm to a few cms.

Radiographic features

Advanced imaging of these lesions allows for differentiation from cystic ovarian neoplasms, which may require surgical therapy .

Ultrasound
  • hyperechoic with a partially hypoechoic rim
    • the rim likely represents a layer of myometrium surrounding the fatty central component
  • posterior acoustic attenuation
  • often poor vascularity on color Doppler examination
CT
  • predominantly fat-containing mass arising from uterus
  • well-marginated 
  • often contains areas of soft tissue density
MRI

Secondary to the predominant fatty component in the lesion, hyperintensity is seen on T1 weighted sequences and chemical shift artifacts are noted. Additionally, fat suppression techniques can be useful in verifying the diagnosis - most of the lesion shows fat suppression . Signal characteristics are, therefore:

  • T1: hyperintensity
  • T1 FS: hypointensity (saturates out)
  • T2: hyperintensity
  • T2 FS or STIR: hypointensity (saturates out)

Treatment and prognosis

Lipoleiomyomas when small and asymptomatic usually do not require treatment and are clinically similar to leiomyomas. Treatment is similar to leiomyomas and is dependent on the clinical symptoms and the size/location of the lesion. Uterine artery embolization or surgical excision can be performed, as indicated . In general, they are benign tumors with favorable prognosis.

History and etymology

The first report as a "myolipoma of soft tissue" was thought to have been described in 1991 by Meis and Enzinger.

Differential diagnosis

General imaging differential considerations include:

  • benign cystic ovarian teratoma
  • malignant degeneration of cystic teratoma
  • non-teratomatous lipomatous ovarian tumor
  • pelvic lipoma 
  • pelvic liposarcoma
  • very rare lipomatous tumors of the uterus:
    • angiomyolipoma of uterus
    • fibromyolipoma of uterus
    • myelolipoma of uterus