Malignant leiomyoblastoma

Uterus
Stromal tumors
Malignant leiomyoblastoma

Author: Mohamed Mokhtar Desouki, M.D., Ph.D. (see Authors page)

Revised: 2 February 2017, last major update August 2011

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed search: malignant leiomyoblastoma

Table of Contents

Cite this page: Malignant leiomyoblastoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusmaligleiomyoblastoma.html. Accessed July 16th, 2017.

Definition / general

Rare but important tumor of uterus and broad ligament
Recurs and metastasizes regardless of mitotic count

Terminology

Also called epithelioid leiomyosarcoma, clear cell leiomyoma

Treatment

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

High MIB-1 index, although mitotic count may be low
Desmin, smooth muscle actin, vimentin, muscle specific actin (HHF35), h-caldesmon (focal staining), human smooth muscle myosin heavy chain (SM1 and SM2), nonmuscle myosin heavy chain (SMemb), ER and PR

Negative stains

Keratin, EMA, CD34, c-kit, S100, myoglobin, myf4, HMB45

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

Endometrial stromal sarcoma with smooth muscle metaplasia
Uterine leiomyoma