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.



  • Rhabdomyosarcoma (RMS)

  • Embryonal rhabdomyosarcoma (ERMS)

  • Alveolar rhabdomyosarcoma (ARMS)


  • Malignant tumor showing variable differentiation toward skeletal muscle



  • 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



  • 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


  • 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


  • 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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