Leiomyosarcoma

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Leiomyosarcoma is a malignant tumour of smooth muscle. It is seen in various places including the uterus and skin.

General

  • Poor prognosis.
  • Do not (generally) arise from leiomyomas.
  • Often singular, i.e. one tumour; unlike leiomyomas (which are often multiple).

Gross

Features:

  • "Fleshy" appearance.
  • Necrosis.
  • Large size.
  • Often singular, i.e. one lesion; leiomyomata are often multiple.

Microscopic

Features:

  • Usu. cellular lesion.
  • Fasciclar arrangement:
    • Whorled look at low power.
    • Groups of spindle cells cut peripendicular to their long axis adjacent to groups of spindle cells cut in the plane of their long axis.
  • Features of malignancy (need all three):
    1. Nuclear atypia.
    2. Tumour cell necrosis.
      • Should be patchy/multifocal.
        • Zonal necrosis is suggestive of vascular cause.
    3. Mitoses - key feature - definitions suffer from HPFitis:
      • >=10 mitoses/HPF - if spindled.[1]
      • >=5 mitoses/HPF - if epithelioid.[1]
      • >=2 mitoses/HPF - if myxoid.[1]
      • >=1 mitosis/HPF - if cutaneous.[2]

Images:

Subtypes

Major variants:[3]

  • Spindled leiomyosarcoma (leiomyosarcoma NOS) - see above.
  • Epithelioid leiomyosarcoma.
  • Myxoid leiomyosarcoma.

Minor variants:[3]

  • Leiomyosarcoma with prominent intravascular growth.
  • Leiomyosarcoma with osteoclast-type cells.
  • Leiomyosarcoma with clear cells.
  • Leiomyosarcoma with xanthoma-type cells.

Epithelioid leiomyosarcoma

Features:[1]

  • >50% epithelial appearance.
  • >=5 mitoses/HPF - definition suffers from HPFitis.

Myxoid leiomyosarcoma

Features:[1]

  • >=2 mitoses/HPF - definition suffers from HPFitis.
  • May have minimal nuclear atypia.

IHC

Features:

  • Positive for SMC markers.
    • Desmin - present in all three types of muscle.
    • H-caldesmon.
    • Smooth muscle myosin.
  • CD10 -ve.

Others:[3]

  • ER, PR, AR +ve -- 30-40% of the time.
  • CD117 +ve/-ve.
  • p53 +ve.
  • MIB-1 high.

See also

References

  1. 1.0 1.1 1.2 1.3 1.4 Nucci, Marisa R.; Oliva, Esther (2009). Gynecologic Pathology: A Volume in Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 281. ISBN 978-0443069208.
  2. Kraft S, Fletcher CD (April 2011). "Atypical intradermal smooth muscle neoplasms: clinicopathologic analysis of 84 cases and a reappraisal of cutaneous "leiomyosarcoma"". Am. J. Surg. Pathol. 35 (4): 599–607. doi:10.1097/PAS.0b013e31820e6093. PMID 21358302.
  3. 3.0 3.1 3.2 3.3 Nucci, Marisa R.; Oliva, Esther (2009). Gynecologic Pathology: A Volume in Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 284. ISBN 978-0443069208.