Leiomyosarcomas are extremely rare malignant neoplasms that originate from smooth muscle cells and may be considered the malignant counterpart of a leiomyoma. They are classified as soft tissue tumours and account for ~8% of malignant soft tissue tumours ¹⁰.

Pathology

Location 

Leiomyosarcomas can potentially occur anywhere there is smooth muscle. Commonly described sites include the following ¹⁴:

• uterine leiomyosarcoma: most common, accounting for up to one-third of uterine sarcomas ⁸

• retroperitoneal leiomyosarcoma: most common extra-uterine site ¹¹

• gastrointestinal tract

  • stomach ¹

  • oesophageal leiomyosarcoma ⁵

  • small intestine

Less common sites include:

• liver: hepatic leiomyosarcoma

• bladder

• nasopharynx 

• bone ⁶: primary leiomyosarcoma of bone

• blood vessels (~2 % of leiomyosarcomas ¹⁴)

  • veins: 5x more common than arteries for vascular leiomyosarcomas ¹⁴

    • inferior vena cava leiomyosarcoma ¹⁰

  • arteries

    • primary pulmonary artery leiomyosarcoma: most common arterial site ¹⁴

    • other sites include aorta, carotid, subclavian, renal, splenic, iliac, femoral (common and superficial), and popliteal arteries ¹⁴

• central nervous system: primary intracranial leiomyosarcoma

• spermatic cord: spermatic cord leiomyosarcoma

• skin: cutaneous leiomyosarcoma ¹³

Radiographic features

Morphological imaging features would be invariably dependent on the site (refer to individual articles). Generally, they tend to be large masses, especially in cases of abdominopelvic lesions ^ref.

CT

• generally heterogeneous ^ref

• commonly demonstrate central low attenuation representing necrosis ¹²

• calcification exceedingly rare ^ref

MRI

The tumour frequently demonstrates cystic foci. Signal characteristics include ^ref:

• T1: isointense to muscle 

• T2: intermediate to hypointense to neighbouring fat 

• T2 FS: predominantly hyperintense 

Differential diagnosis

For a meaningful differential, it is necessary to consider site-specific tumours.