Soft tissue
Skeletal muscle
Rhabdomyosarcoma - general

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

Revised: 26 September 2016, last major update November 2012

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

PubMed Search: Rhabdomyosarcoma [title] soft tissue

Definition / General
  • Primitive malignant soft tissue sarcoma with skeletal muscle phenotype by H&E, immunohistochemistry or EM
  • Subtypes: alveolar, anaplastic, embryonal, pleomorphic, sclerosing (Mod Pathol 2001;14:506), although mixtures are common
  • Note: some alveolar and embryonal tumors have similar gene expression (Am J Pathol 2009;174:550)

Rhabdomyoblast
  • Cell of origin for rhabdomyosarcomas
  • Eccentric eosinophilic granular cytoplasm rich in thick and thin filaments
  • If round and elongate, are called strap cells or tadpole cells
Epidemiology
  • Most common soft tissue sarcoma of childhood/adolescence (5 - 8% of solid pediatric tumors, 50% of pediatric soft tissue sarcomas)
  • 50% at 0 - 9 years
  • Children 2 - 6 years usually have head, neck or GU tumors
  • Teenagers usually have paratesticular, trunk or abdominal tumors
  • Relatively rare in adults, who often have pleomorphic and NOS subtypes
  • Slight male predominance (M/F: 1.3:1)
  • Head and neck tumor are more often embryonal types
  • Extremity tumors more often have alveolar histologic type
  • 80% of genitourinary RMS are embryonal type
  • Usually > 5 cm at diagnosis
Clinical Features
Treatment
  • International Classification of Rhabdomyosarcoma (Cancer 1995;76:1073)
    • Superior prognosis: botryoid, spindle cell
    • Intermediate prognosis: embryonal
    • Poor prognosis: alveolar, undifferentiated sarcoma

  • Adults have poorer 5 year survival (27%) than children (61%, J Clin Oncol 2009;27:3391)
  • Poorer overall 5 year survival in hand/foot (33% versus 56% overall) due to marked tendency to spread and inability to completely excise (Pediatr Hematol Oncol 2009;26:321)
  • Poorer survival in childhood embryonal (intermediate-risk) tumors if anaplasia is present (Cancer 2008;113:3242)
  • Five year survival has increased from periods 1976-1980 to 1996-2000 for rhabdomyosarcoma overall (53% to 62%), embryonal (61% to 73%) and alveolar subtypes (40% to 48%, Cancer 2009;115:4218)
  • Pathologists should compare post-treatment to pre-treatment specimens (Am J Clin Pathol 2005;123:75)
Micro Images

Images hosted on other servers:

Various images

Positive Stains
  • Recommended panel contains myogenin, sarcomeric actin (90%) and desmin (95%)
  • Desmin: reliable for solid variant of alveolar rhabdomyosarcoma, tumors with round or strap cell rhabdomyoblasts, also smooth muscle tumors
  • Myoglobin: specific, but only found in better differentiated tumors, may be non-specific due to diffusion from adjacent injured skeletal muscle cells
  • Myogenin: sensitive and specific, particularly useful for alveolar subtype (Mod Pathol 2000;13:988)
  • MyoD1
  • Vimentin (not specific)
Negative Stains
Electron Microscopy Description
  • Rhabdomyoblasts contain sarcomeres (thick and thin filaments) and Z bands