fibroids

Uterine leiomyomas also referred to as uterine fibroids, are benign tumors of myometrial origin and are the most common solid benign uterine neoplasms. Commonly an incidental finding on imaging, they rarely cause a diagnostic dilemma. There are various medical, surgical, and interventional treatment options.

Epidemiology

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

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

Clinical presentation

They are often asymptomatic and discovered incidentally. Signs and symptoms associated with fibroids include:

  • abnormal vaginal bleeding
  • pain
  • infertility
  • palpable masses

Pathology

Leiomyomas are benign monoclonal tumors  predominantly composed of smooth muscle cells with variable amounts of fibrous connective tissue. They are commonly multiple (~85% ), 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 hemorrhage, fibrosis, and calcification.

They can also undergo several types of degeneration:

Based on histology

Radiographic features

Plain radiograph

Popcorn calcification within the pelvis may suggest the diagnosis.

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
  • Venetian blind artefact may be seen but edge shadowing +/- dense posterior shadowing from calcification is also typically seen
CT
  • fibroids are usually seen as soft tissue density lesions and may exhibit coarse peripheral or central calcification
  • they may distort the usually smooth uterine contour
  • enhancement pattern is variable
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 characterizing fibroids. Size, location, and signal intensity should be noted.

Signal characteristics are variable and include :

  • 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
    • 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
  • T1 C+ (Gd)
    • variable enhancement is seen with contrast administration
    • the 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.

Treatment and prognosis

Common treatment options include:

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

Differential diagnosis

General imaging differential considerations include:

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