Uterine leiomyoma

Uterine leiomyomas (uterine fibroids) are benign tumours of myometrial origin and are the most common solid benign uterine neoplasm. Commonly an incidental finding on imaging, and they rarely cause a diagnostic dilemma. There are various medical, surgical and interventional treatment options.


They occur in ~25% of women of reproductive age 1 and are particularly common in the African population.

Fibroids are responsive to hormones (e.g. stimulated by oestrogens). Being rare in prepubertal females, they commonly accelerate in growth during pregnancy and involute with menopause 1.

Clinical presentation

Often asymptomatic and discovered incidentally. Signs and symptoms associated with fibroids include:

  • abnormal vaginal bleeding
  • pain
  • infertility
  • palpable masses


Leiomyomas are benign monoclonal tumours 16 predominantly composed of smooth muscle cells with variable amounts of fibrous connective tissue. They are commonly multiple (~85% 8), and range significantly in size.

Fibroids may have a number of locations within or external to the uterus:

Subserosal fibroids may be pedunculated and predominantly extra-uterine, simulating an adnexal mass. Any fibroid may undergo atrophy, internal haemorrhage, fibrosis, and calcification.

They can also undergo several types of degeneration:

  • hyaline degeneration: focal or generalized hyalinization: this is the most common type of degeneration (can occur in ~60% of cases) 6
  • cystic degeneration: ~5%
  • myxoid degeneration: generally considered uncommon although reported as high a 50% by some authors 14
  • red/carneous degeneration: due to haemorrhagic infarction, which can occur particularly during pregnancy, and may present with acute abdominal pain
Based on histology

Radiographic features

Plain radiograph

Popcorn calcification within the pelvis may suggest the diagnosis.

Pelvic ultrasound
  • ultrasound is used to diagnose the presence and monitor the growth of fibroids
  • uncomplicated leiomyomas are usually hypoechoic, but can be isoechoic, or even hyperechoic compared to normal myometrium
  • calcification is seen as echogenic foci with shadowing
  • cystic areas of necrosis or degeneration may be seen
  • on CT images, fibroids are usually of soft tissue density but may exhibit coarse peripheral or central calcification
  • they may distort the usually smooth uterine contour
  • enhancement pattern is variable
Pelvic MRI

MRI is not generally required for diagnosis, except for complex or problem-solving cases. It is, however, the most accurate modality for detecting, localizing and characterising fibroids. Size, location and signal intensity should be noted.

Signal characteristics are variable and include 1-2:

  • T1
    • non-degenerated fibroids and calcification appear as low to intermediate signal intensity compared with the normal myometrium
    • characteristic high signal intensity on T1 weighted images/an irregular, T1 hyperintense rim around a centrally located myoma suggests red degeneration, which is caused by venous thrombosis
  • T2
    • non-degenerated fibroids and calcification appear as low signal intensity
    • as they are usually hypervascular, flow voids are often observed around them 10
    • fibroids that have undergone cystic degeneration/necrosis can have a variable appearance, usually appearing high signal on T2 sequences.
    • hyaline degeneration is demonstrated as low T2 signal intensity
    • cystic degeneration, which is an advanced stage of intratumoral edema, also shows high signal intensity on T2 weighted images and does not enhance 10
  • T1 C+ (Gd)
    • variable enhancement is seen with contrast administration
    • marked high signal intensity with gradual enhancement (albeit mild) suggests myxoid degeneration

MRI is of significant value in the symptomatic patient when surgery and uterine salvage therapy is considered. It is also of great value in differentiating a pedunculated fibroid from an adnexal mass 5.

Treatment and prognosis

Common treatment options include:

  • rarely invasion of adjacent venous channels leading to intravenous leiomyomatosis 15
  • rarely (0.1-0.5%), they undergo malignant degeneration into leiomyosarcomas
  • in extremely rare instances, lesions capable of metastasising without malignant transformation: benign metastasising leiomyoma 3
  • fibroids may torse, leading to acute pelvic pain
  • pregnancy may cause fibroid growth in 30%

Differential diagnosis

General imaging differential considerations include:

On occasional situations it may be difficult to differentiate between uterine leiomyomas and:

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