Cutaneous Rhabdomyosarcoma



Cutaneous Rhabdomyosarcoma


Khin Thway, BSc, MBBS, FRCPath










This cutaneous RMS from the ear is a polypoidal tumor with extensive infiltration of the dermis by hypercellular sheets of fairly uniform, small, hyperchromatic, ovoid cells.






High magnification of a cutaneous RMS shows a nodular dermal proliferation of medium-sized, blue-staining, ovoid cells. A grenz zone separates the tumor from overlying epidermis.


TERMINOLOGY


Abbreviations



  • Rhabdomyosarcoma (RMS)


  • Embryonal rhabdomyosarcoma (ERMS)


  • Alveolar rhabdomyosarcoma (ARMS)


Definitions



  • Malignant tumor showing variable differentiation toward skeletal muscle


ETIOLOGY/PATHOGENESIS


Unknown



  • Cell of origin still unknown



    • Possible candidate cells include muscle stem cells and multipotent mesenchymal stem cells


  • Often occurs in sites lacking skeletal muscle


  • May occur in association with inherited syndromes



    • e.g., Beckwith-Wiedemann


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rhabdomyosarcomas are most frequent soft tissue sarcomas in children and young adults


    • Occurrence in skin is rare



      • May occur as metastasis from primary site


      • May very rarely occur as primary cutaneous lesion


      • ARMS, ERMS, and pleomorphic RMS may all occur as primary neoplasms in the skin


    • ERMS is most common RMS subtype



      • Represents 60-70% of RMS


    • Alveolar RMS



      • Approximately 30% of RMS


    • Pleomorphic RMS



      • Rarer amongst pleomorphic sarcomas


  • Age



    • RMS occurs most often in children and young adults


    • Cutaneous RMS occurs mostly in children (including congenitally and in infants) and young people



      • However, can occur in all age groups


    • ERMS generally affects youngest population



      • Typically < 10 years


    • ARMS



      • Adolescents and young adults


    • Pleomorphic RMS



      • Older adults


    • Spindle cell RMS



      • Rare variant in children and adolescents; rarely adults


  • Gender



    • M = F


Site



  • May occur at any cutaneous site



    • Including head and neck, trunk, extremities


  • Small numbers arise as heterologous elements of other skin tumors



    • e.g., within congenital melanocytic nevi


    • e.g., in Merkel cell carcinoma


  • Embryonal RMS



    • Most common soft tissue sites include head and neck, pelvis (including genitourinary region), and bile duct


    • Trunk and limbs less frequently involved than in ARMS


  • Alveolar RMS



    • Extremities, trunk, head and neck


  • Spindle cell RMS



    • Paratesticular region, head and neck


  • Pleomorphic RMS



    • Extremities


Presentation



  • Mass, NOS



    • Often presents as asymptomatic papule or nodule




      • May cause pain


    • Nonspecific clinical features



      • Diagnosis may therefore be delayed

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Cutaneous Rhabdomyosarcoma
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