Elizabeth A. Montgomery, MD

This leiomyosarcoma extended into the subcutis. It is composed of perpendicularly oriented fascicles of brightly eosinophilic cells. At scanning magnification, atypical nuclei stand out image.

There is no need to search for numerous mitoses to diagnose leiomyosarcoma, although mitotic counts assist in assigning a sarcoma grade. Note the bright pink color of the cytoplasm.



  • Leiomyosarcoma (LMS)


  • Malignant neoplasm composed of cells exhibiting smooth muscle differentiation


Infectious Agents

  • Epstein-Barr virus (EBV) associated in immunosuppressed patients

  • Occasional examples are radiation associated



  • Incidence

    • Uncommon: 10-15% of extremity sarcomas

    • Most common overall sarcoma type if uterine and visceral examples are included

  • Age

    • Middle-aged adults

  • Gender

    • No gender preference overall


  • Cutaneous LMS presents as a single nodule or plaque-like tumor

    • May be ulcerated or show serum crusting/hemorrhage

  • Deep soft tissue tumors present as a mass, often asymptomatic, in extremities

    • Retroperitoneum most common site

    • Vena cava examples often symptomatic

  • Uterine examples considered separately with unique diagnostic criteria


  • Surgical excision

    • Radiation

    • Chemotherapy for metastatic tumors


  • Outcome site and stage dependent as with other sarcoma types

    • Lesions restricted to cutis essentially never metastasize

      • Some observers have advocated diagnosing them as “atypical smooth muscle tumors”

    • Subcutaneous lesions

      • Up to 1/3 of tumors metastasize

      • 10-20% of patients with subcutaneous lesion die of disease

    • Retroperitoneum: About 80% of patients die of disease, typically with metastases

    • Bone: Metastases in up to 1/2 of patients

    • Vena cava: 5- and 10-year survival 50% and 30%, respectively

    • Head and neck: Over 1/2 metastasize


Histologic Features

  • Perpendicularly oriented fascicles of spindle cells

  • Cells show brightly eosinophilic cytoplasm

  • Blunt-ended nuclei with nuclear atypia

  • Some examples are epithelioid-appearing

  • Any number of mitoses sufficient in subcutis, scrotal lesions, or deep soft tissue if nuclear atypia is present

  • In vulva, some observers offered > 5 mitosis per 10 HPF as “cutoff,” but recurrences reported in lesions with any mitotic activity

Predominant Pattern/Injury Type

  • Fascicular

Predominant Cell/Compartment Type

  • Mesenchymal, smooth muscle

Variant and Special Forms

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Leiomyosarcoma

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