Leiomyosarcoma

Leiomyosarcomas (LMS) 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:

• 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 leimyosarcoma of bone
• venous structures: vascular leiyomyosarcoma(s) ¹⁰
  • inferior vena cava
  • renal vein
• 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 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

May frequently demonstrate cystic foci within. 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.