Soft tissue
Skeletal muscle
Pleomorphic rhabdomyosarcoma

Author: Vijay Shankar, M.D. (see Authors page)

Revised: 26 September 2016, last major update November 2012

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Pleomorphic rhabdomyosarcoma [title]

Cite this page: Pleomorphic rhabdomyosarcoma. website. Accessed December 14th, 2017.
Definition / general
  • High grade sarcoma of adults with bizarre polygonal, round or spindle cells, with skeletal muscle differentiation and no alveolar or embryonal component
  • Rarely has smooth muscle or fibrohistiocytic differentiation (Ultrastruct Pathol 2010;34:42)
  • Rare, but common rhabdomyosarcoma subtype in adults
  • Usually age 50+; can occur in children (Ann Diagn Pathol 2001;5:199), but then called anaplastic
  • 70% male
Clinical features
  • Rapidly growing painful mass, most commonly of lower extremity, abdomen / retroperitoneum, chest / abdominal wall or spermatic cord / testes, uterine corpus, upper extremity, orbit
  • Similar behavior to other pleomorphic sarcomas
  • Must prove skeletal muscle differentiation by cross striations or skeletal muscle marker immunoreactivity
  • No alveolar or embryonal component
  • Common errors involve entrapped skeletal muscle, non-specific myoglobin immunoreactivity or skeletal muscle differentiation of other tumors
Case reports
Clinical images

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Face, courtesy of Mark R. Wick, M.D.

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

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Microscopic (histologic) description
  • Well circumscribed
  • Large, multinucleated, bizarre, eosinophilic tumor cells
  • Should see cross striations or have immunohistochemical evidence of skeletal muscle differentiation
  • No alveolar or embryonal component (by definition)
  • Classic type: predominantly atypical rhabdomyoblasts in sheets
  • Round cell type: clusters of rhabdomyoblasts in background of slightly atypical, medium sized, round blue rhabdomyoblasts
  • Spindle cell type: scattered rhabdomyoblasts with predominantly atypical spindled rhabdomyoblasts in storiform pattern
Microscopic (histologic) images

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Fascicular pattern

Storiform pattern

Patternless pattern

Hemangioper-icytoma-like pattern

Spindle cells

Pleomorphic and polygonal cells

Epithelioid cells with abundant eosinophilic cytoplasm

Clear cytoplasm due to washing out of glycogen

Images courtesy of Mark R. Wick, M.D.:


Spindle cell


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Classic, round cell and spindle cell variants

Abundant eosinophilic cytoplasm

Evidence of differentiation

Various stains

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 hosted on PathOut servers:

Courtesy of Mark R. Wick, M.D.

Images hosted on other servers:

Thick and thin filaments from primitive Z bands

Molecular / cytogenetics description
Differential diagnosis