Table of ContentsDefinition / general | Essential features | Terminology | Epidemiology | Sites | Etiology | Clinical features | Prognostic factors | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Board review style question #1 | Board review style answer #1
Cite this page: Gonzalez RS. Leiomyosarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorLMS.html. Accessed April 19th, 2021.
Definition / general
- Malignant smooth muscle tumor of colon
- Rare, with poor prognosis
- Arises in muscularis propria (Mod Pathol 2015;28 Suppl 1:S47)
- Most older reports of colonic leiomyosarcomas were probably GIST
- Rare in colon; less common than GIST (Am J Surg Pathol 2000;24:1339)
- Small intestine and colon most common GI sites for leiomyosarcoma
- Adult patients often die of disease
- Tumors in infants may have more favorable prognosis (J Pediatr Surg 2004;39:1257)
- Tumor size > 5 cm suggests poor prognosis (Histopathology 2013;63:194)
- Surgical resection, including of metastases (J Gastrointest Oncol 2015;6:E70)
- Intraluminal, bulging / polypoid mass measuring up to 25 cm
Microscopic (histologic) description
- Resembles leiomyosarcoma at other sites: malignant smooth muscle cells with prominent nuclear atypia, coagulative necrosis and at least 1 mitosis per 10 high power fields
- Rare examples have osteoclast-like giant cells (Arch Pathol Lab Med 2004;128:440)
Microscopic (histologic) images
Molecular / cytogenetics description
- Negative for KIT mutations
Sample pathology report
- Transverse colon, resection:
- Leiomyosarcoma (4.7 cm) (see comment)
- Margins of resection unremarkable.
- Three benign lymph nodes.
- Comment: The tumor shows prominent nuclear atypia, numerous mitotic figures and regions of necrosis. Immunohistochemical stains for SMA and desmin are positive in the tumor. Leiomyosarcomas are rare in the colon and risk factors for progression in this location remain poorly defined.
Board review style question #1