Soft tissue
Skeletal muscle
Pleomorphic rhabdomyosarcoma

Author: Erdener Özer, M.D., Ph.D. (see Authors page)

Revised: 7 February 2018, last major update February 2018

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

PubMed Search: Pleomorphic rhabdomyosarcoma[TI]

Cite this page: Özer, E. Pleomorphic rhabdomyosarcoma. website. Accessed February 17th, 2018.
Definition / general
  • High grade sarcoma composed of undifferentiated atypical cells that display skeletal muscle differentiation without embryonal or alveolar components
  • Exceedingly rare category of rhabdomyosarcoma (RMS) in adults
  • Not well characterized in the pediatric population; many of these cases can be considered RMS with diffuse anaplasia
Essential features
  • Tumor cells must have skeletal muscle differentiation proven by cross striations or skeletal muscle marker immunoreactivity
  • Usually older than 50
  • 70% male
Clinical features
  • Rapidly growing, painful mass, most commonly of lower extremity
Radiology images

Images hosted on other servers:


Case reports
  • Clinical behavior and responsiveness to chemotherapy are similar to adult high grade soft tissue sarcomas
  • Poor prognosis; 70% die of disease after mean follow up of 20 months (Mod Pathol 2001;14:595)
Clinical images

Images contributed by Mark R. Wick, M.D.:


Images hosted on other servers:

Scrotal mass

Gross description
  • Mean 7 cm, up to 30 cm
  • White firm cut surface with variable hemorrhage and necrosis
  • May be confined to fascial compartment and assume shape of muscle from which it arises
Gross images

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Paratesticular tumors

Resected tumor

Microscopic (histologic) description
  • Classic type: large, multinucleated, bizarre, eosinophilic and polygonal cells with¬†predominantly atypical rhabdomyoblasts in sheets
  • Round cell type:¬†clusters of rhabdomyoblasts in background of slightly atypical, medium sized, round rhabdomyoblasts
  • Spindle cell type:¬†scattered rhabdomyoblasts with predominantly atypical spindled rhabdomyoblasts in storiform pattern
Microscopic (histologic) images

Images contributed by Burcin Tuna, M.D.:

H&E, x10

H&E, x20

Desmin, x10

MyoD1, x20

AFIP images:

Fascicular pattern

Storiform pattern

Patternless pattern

Hemangioperi-cytoma-like pattern

Spindle cells

Pleomorphic and polygonal cells

Epithelioid cells with abundant eosinophilic cytoplasm

Clear cytoplasm due to washing out of glycogen

Images contributed by Mark R. Wick, M.D.:


Positive stains
Electron microscopy description
  • Skeletal muscle differentiation with rudimentary sarcomeres containing Z bands or Z band material with thick and thin filaments
Electron microscopy images

Images contributed by Mark R. Wick, M.D.:
Molecular / cytogenetics description
Differential diagnosis
Board review question #1
Which feature is a requirement for diagnosis of pleomorphic rhabdomyosarcoma?

  1. Anaplasia
  2. Embryonal or alveolar components
  3. Extensive necrosis
  4. PAX3-FOXO1 fusion gene
  5. Skeletal muscle differentiation
Board review answer #1
E. Skeletal muscle differentiation