Pleomorphic rhabdomyosarcoma

Pleomorphic rhabdomyosarcoma is a type of rhabdomyosarcoma, and is the least common, accounting for only 5% of all rhabdomyosarcomas. Unlike embryonal and pleomorphic types, these tumors occur in adults over the age of 40 years 1, and are difficult to distinguish from other pleomorphic sarcomas such as malignant fibrous histiocytomas 2.

Some publications divide into 3 specific types

  • classic: predominantly atypical  pleomorphic polygonal rhabdomyoblasts (PRMB) in sheets
  • round cell: clusters of PRMB throughout the tumor with a background of slightly atypical, medium-sized, round, blue RMB
  • spindle cell: scattered PRMB in a predominance of atypical spindled RMB arranged in a storiform growth pattern.

Can reveal the following to varying proportions:

  • myoglobin: common
  • MyoD1
  • skeletal muscle myogenin (myf4)
  • fast skeletal muscle myosin
  • desmin
  • muscle-specific actin
  • smooth muscle actin (SMA)
  • muscle specific myogenin (myf3)

They typically occur in the limbs, with a predilection for the thigh 2.

The features are non-specific (see radiographic features in the parent article: rhabdomyosarcoma), although in general pleomorphic rhabdomyosarcomas have multiple areas of necrosis. In some instances, these areas are surrounded by pronounced ring-like enhancement 1.

It is considered a high-grade sarcoma, with an aggressive clinical course 3.

Article information

rID: 8326
Tag: cases, cases
Synonyms or Alternate Spellings:
  • Pleomorphic rhabdomyosarcomas
  • Pleomorphic rhabdomyosarcoma (PRMS)

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