Soft tissue
Skeletal muscle
Anaplastic rhabdomyosarcoma

Author: Erdener Özer, M.D., Ph.D.

Revised: 30 January 2018 last major update October 2017

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Anaplastic rhabdomyosarcoma "loattrfree full text"[sb]

Cite this page: Özer, E. Anaplastic rhabdomyosarcoma. website. Accessed April 25th, 2018.
Definition / general
Essential features
  • Presence of pleomorphic cells with large, lobate hyperchromatic nuclei and atypical (multipolar) mitotic figures
  • These tumors display high heterogeneity and extremely poor differentiation
  • Anaplastic cells may be focal or diffuse
    • Focal anaplasia: anaplastic cells are loosely scattered among nonanaplastic cells
    • Diffuse anaplasia: anaplastic cells are aggregated in clusters or form continuous sheets (Am J Surg Pathol 1993;17:443)
  • Anaplastic rhabdomyosarcoma (in children)
  • Undifferentiated rhabdomyosarcoma
  • Rhabdomyosarcoma with anaplasia
  • Often found in the extremities
Radiology images

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Congenital tumor
on abdomen

Prognostic factors
Case reports
  • Most aggressive subtype of rhabdomyosarcoma
  • Often requires intensive treatment (Cancer 2008;113:3242)
Clinical images

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Congenital tumor
on abdomen

Microscopic (histologic) description
  • Enlarged atypical cells with hyperchromatic nuclei (3x larger than nuclei in neighboring tumor cells), often with atypical mitotic figures
  • May be focal or diffuse
  • Classic embryonal rhabdomyosarcoma may be present
Microscopic (histologic) images

Images hosted on PathologyOutlines server:

Extremely hyperchromatic nuclei are 3x larger than nuclei of adjacent tumor cells, mixed with smaller, undifferentiated, round and spindle cells

Bizarre mitotic figure (left side)

Rare cells suggest skeletal muscle differentiation

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Anaplastic rhabdomyosarcoma

Cytology images

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Positive stains
  • Muscle specific actin (80%), desmin (60%)
Molecular / cytogenetics description
Board review question #1
The WHO entity pleomorphic rhabdomyosarcoma is not considered a separate diagnosis in pediatric patients, instead being incorporated with which of the following?

  1. Diffuse anaplasia
  2. Extensive necrosis
  3. High MIB index
  4. Increased mitotic activity
  5. Poor differentiation
Board review answer #1
A. Diffuse anaplasia