Stromal tumors
Malignant leiomyoblastoma

Topic Completed: 1 August 2011

Revised: 25 February 2019

Copyright: 2002-2017, PathologyOutlines.com, Inc.

PubMed search: malignant leiomyoblastoma

Mohamed Mokhtar Desouki, M.D., Ph.D.
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Cite this page: Desouki M. Malignant leiomyoblastoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusmaligleiomyoblastoma.html. Accessed September 17th, 2019.
Definition / general
  • Rare but important tumor of uterus and broad ligament
  • Recurs and metastasizes regardless of mitotic count
  • Also called epithelioid leiomyosarcoma, clear cell leiomyoma
  • Hysterectomy, bilateral salpingo-oophorectomy and debulking
  • Radio- and chemotherapy are not effective
  • Hormonal therapy used in a few cases
Gross description
  • Gelatinous, well circumscribed
Microscopic (histologic) description
  • Invasive and infiltrative, highly myxomatous
  • Rounded to polygonal shaped cells and mixtures of epithelioid and clear cells in a plexiform pattern
  • Tumor cells have moderate to marked atypia, but variable tumor cell necrosis
Positive stains
Negative stains
Electron microscopy description
  • Immature smooth muscle differentiation that mimics mesenchymal cells of fetal uterus (Histopathology 2003;42:379)
  • Many tumour cells do not exhibit specific differentiation
  • Bundles of thin filaments with or without focal densities are present in scattered tumor cells
  • Thin filaments are well developed
  • Intermediate filaments and thin filaments are closely intermingled and occasionally form distinctive complexes with many irregular, dense body-like structures
  • Mitochondria, rough endoplasmic reticulum and free ribosomes are common
Differential diagnosis
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