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Rhabdomyosarcoma | Radiology Key

Rhabdomyosarcoma



Rhabdomyosarcoma


Bernadette L. Koch, MD









Figure 1 (Left) Coronal CECT in a 5 year old shows a well-defined, mildly enhancing left orbital rhabdomyosarcoma image, inseparable from the left inferior rectus muscle. Notice contralateral normal inferior rectus muscle image. (Right) Coronal T1WI C+ FS MR in an 11-year-old boy with recurrent parameningeal rhabdomyosarcoma image shows intracranial extension involving the cavernous sinuses bilaterally and the right middle cranial fossa image.






Figure 2 (Left) Axial CECT in a 2-year-old girl with nasal ala RMSa image shows a well-defined mass narrowing the right anterior nasal cavity, without significant bone destruction. Lack of bone destruction in a young child with a soft tissue mass should not be interpreted as diagnostic of a benign lesion. (Right) Axial CECT in an 11 year old with left facial mass and prior history of RMSa demonstrates a large, necrotic, left masticator space recurrence image and destruction of the mandible image.



TERMINOLOGY


Abbreviations



  • Rhabdomyosarcoma (RMSa)


Definitions



  • Malignant neoplasm of striated muscle; most common childhood soft tissue sarcoma


IMAGING


General Features



  • Best diagnostic clue



    • Soft tissue mass with variable contrast enhancement


    • Bone destruction or remodeling possible


  • Location



    • Up to 40% occur in head & neck (H&N)



      • Orbit


      • Parameningeal sites: Middle ear, paranasal sinus, nasopharynx (NP), masticator space, pterygopalatine fossa, parapharyngeal space



        • Intracranial extension in up to 55%


      • All other head & neck sites including cervical neck, nasal cavity


  • Size



    • Variable, may present earlier in orbit secondary to small space and early proptosis


CT Findings



  • Invasive soft tissue mass with variable contrast enhancement


  • Osseous erosion common but not seen in all cases


MR Findings



  • Isointense T1, hyperintense T2 relative to muscle


  • Variable contrast enhancement


  • Intracranial extension in parameningeal RMSa



    • Meningeal thickening and enhancement


Imaging Recommendations



  • Best imaging tool



    • CT best to evaluate osseous erosion


    • MR best to evaluate intracranial & perineural spread


  • Protocol advice



    • Coronal post-contrast fat-saturation T1 imaging for assessment of intracranial disease


    • Axial and coronal thin section bone CT for osseous erosion


    • Include neck to rule out cervical metastatic adenopathy


DIFFERENTIAL DIAGNOSIS


Juvenile Angiofibroma

Sep 20, 2016 | Posted by in HEAD & NECK IMAGING | Comments Off on Rhabdomyosarcoma
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