Leiomyosarcoma

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 a soft tissue tumor and account for ~8% of malignant soft tissue tumors ¹⁰.

Pathology

Location 

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

• uterus: uterine leiomyosarcoma: most common (account for up to one-third of uterine sarcomas ⁸)
• retroperitoneum: retroperitoneal leiomyosarcoma; most common non-uterine site ¹¹
• stomach ¹: gastric leiomyosarcoma
• esophagus ⁵: esophageal leiomyosarcoma  
• small intestine: leiomyosarcoma of the small intestine 
• liver: hepatic leiomyosarcoma
• bladder
• nasopharynx 
• bone ⁶: primary leiomyosarcoma of bone
• venous structures ¹⁰
  • inferior vena cava leiomyosarcoma
  • pulmonary artery leiomyosarcoma
• central nervous system: primary intracranial leiomyosarcoma

Other sites include

• spermatic cord: spermatic cord leiomyosarcoma
• pulmonary artery: primary pulmonary artery leiomyosarcoma

Radiographic features

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

CT

• generally heterogeneous
• commonly demonstrate central low attenuation representing necrosis ¹²
• calcification exceedingly rare

MRI

The tumor frequently demonstrates cystic foci. Signal characteristics include 

• T1: isointense to muscle 
• T2 non-fat suppressed: intermediate to hypointense to neighboring fat 
• T2 FS: predominantly hyperintense 

Differential diagnosis

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