Smooth muscle tumor

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Author: Mikael Häggström [note 1]

Smooth muscle tumor (in this case leiomyoma).


On this resource, the following formatting is used for comprehensiveness:

  • Minimal depth
  • (Moderate depth)
  • ((Comprehensive))

Gross processing

Gross examination

Fibroid locations.

When finding fibroids (spherical tumors with whorled pattern, which in the uterus can be presumed to be smooth muscle tumors), examine and describe:[1]

  • Location. If in the uterus:
  • Intramural/submucosal/subserosal (see image)
  • (Posterior/anterior/right or left lateral.)
  • Number of tumors, if multiple. May be described simply as "multiple".
  • Size (may be described as "up to ___ cm in greatest dimension".
  • (Presence or absence of any hemorrhage or necrosis.)
  • ((Demarcation))


In case of hysterectomy, submit pieces from all fibroids >5 cm in diameter.[1]

Submit any macroscopically abnormal parts of the fibroids (hemorrhagic, necrotic, brittle or softening areas, and areas with blurry delimitation).[1]

For fibroids that are significantly calcified, a gross-only description as a calcified fibroid is generally sufficient, without the need to decalcify it to dissect it or sample from it.[note 2]

Microscopic examination

Distinguish leiomyoma (benign) from leiomyosarcoma (malignant) by looking at the latter's criteria:[2]

  • Marked cellular atypia
  • Mitoses: > 10 mitoses/10 high power fields
  • Necrosis

Diagnosis of conventional leiomyosarcoma requires 2 of these 3 histologic features.[2]

Further information: Evaluation of tumors

Microscopic report


  • Microscopic findings, including any visible linings
  • Diagnosis or most probable one
  • Any linings or borders.

Example, for a cervical polyp:

Polyp lined by a single layer of columnar epithelium consistent with endometrium. The interior consists of smooth muscles in a whorled pattern. No atypia. The finding is consistent with a pedunculated submucosal leiomyoma.

  See also: General notes on reporting


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.
  2. When a fibroid has calcifications it has been there a long time, and can be assumed to be benign.

Main page


  1. 1.0 1.1 1.2 Monica Dahlgren, Janne Malina, Anna Måsbäck, Otto Ljungberg. Stora utskärningen. KVAST (Swedish Society of Pathology). Retrieved on 2019-09-26.
  2. 2.0 2.1 Paulette Mhawech-Fauceglia, M.D.. Uterus - Smooth muscle tumors - Leiomyosarcoma. Pathology Outlines. Topic Completed: 5 December 2019. Minor changes: 11 August 2020
  3. Mohamed Mokhtar Desouki. Uterus - Stromal tumors - Leiomyoma. Pathology Outlines. Topic Completed: 1 August 2011. Revised: 15 December 2019
  4. Vijay Shankar, M.D.. Soft tissue - Smooth muscle - Leiomyosarcoma - general. Pathology Outlines. Topic Completed: 1 November 2012. Revised: 11 September 2019

Image sources