Spindle Cell Rhabdomyosarcoma

Spindle Cell Rhabdomyosarcoma

Khin Thway, BSc, MBBS, FRCPath

Low-power view of adult-type spindle cell rhabdomyosarcoma, in which laryngeal squamous epithelium overlies cellular tumor, shows sheets of mildly atypical cells within collagenous stroma.

Juvenile-type spindle cell rhabdomyosarcoma shows sweeping fascicles of spindled cells present in a collagenous matrix. Focal rhabdomyoblastic differentiation is evident image, even at low power.



  • Spindle cell rhabdomyosarcoma (RMS)


  • Uncommon subtype of rhabdomyosarcoma occurring in both children and adults; composed of largely cellular proliferation of predominantly spindled cells

  • Spindle cell RMS in children is considered variant of embryonal RMS

    • Carries good prognosis compared to other RMS subtypes

  • Adult-type spindle cell rhabdomyosarcoma is aggressive neoplasm



  • Age

    • Children

      • < 10 years

    • Adults

      • All adult age groups (2nd-8th decades)

      • Median: Approximately 4th-5th decades

  • Gender

    • Male preponderance


  • Children

    • Most tumors occur in paratesticular region

  • Adults

    • Most common in head and neck region

      • > 50% of cases

    • Retroperitoneum

    • Extremities

    • Trunk

    • Vulva

    • Paratesticular region

  • Tumors usually deeply located


  • Suddenly enlarging mass

    • Local symptoms pertaining to site of origin


  • Behavior varies significantly between children and adults, suggesting distinct clinicopathologic subtypes

    • Good prognosis in children (when compared to other RMS subtypes)

    • Clinically aggressive in adults

      • Lymph node or blood-borne metastases


General Features

  • Firm white mass


  • Variable: 1-30 cm

    • Mean: 8 cm


Histologic Features

  • Juvenile type

    • Fascicular architecture

      • Sweeping or loose fascicles

      • Some tumors have storiform pattern

    • Usually hypercellular

    • Spindle cells

      • Elongated nuclei

      • Nuclei can be vesicular or hyperchromatic

      • Nucleoli may be prominent

      • Pale or amphophilic fibrillary cytoplasm

      • Cross-striations

      • Prominent cell borders

    • Rhabdomyoblasts

      • Variable numbers

      • Spindle or polygonal

    • Variable amounts of intervening collagen

      • Collagen-rich type shows abundant collagen fibers, with cells in short fascicles or storiform arrangements

      • Collagen-poor type is more cellular

    • Mitotic figures usually prominent

    • Frankly pleomorphic areas absent

    • No round cell foci

  • Adult type

    • Long or intersecting fascicles

    • Atypical spindle cells

      • Elongated, vesicular nuclei

      • Pale or amphophilic fibrillary cytoplasm

    • Scattered spindle or polygonal rhabdomyoblasts

      • Usually present in small numbers

      • Abundant eosinophilic cytoplasm

    • Prominent mitoses with atypical forms

    • Necrosis in some tumors

      • Sclerosing pseudovascular features in a smaller number

    • No round cell or pleomorphic areas



  • Desmin(+)

    • Characteristically strong and diffuse cytoplasmic expression

  • Myogenin(+) and MYOD1(+)

    • Myogenic nuclear regulatory proteins

    • Nuclear expression is specific for RMS

      • May be scanty or focal

    • Any cytoplasmic staining should be disregarded

  • HHF-35 (muscle specific actin)(+)

  • SMA frequently positive

  • Occasional cases cytokeratin and epithelial membrane antigen positive

  • H-caldesmon(-)

  • S100 protein(-)



  • Predilection for head and neck

    • Especially fetal type

  • Fetal rhabdomyoma

    • No atypia or necrosis

    • Mitoses usually absent

  • Adult rhabdomyoma

    • Male preponderance

    • Circumscribed lesion

    • Large polygonal cells, abundant cytoplasm

  • Genital rhabdomyoma

    • Mostly middle-aged women

    • Mostly vagina; also vulva and cervix

Desmoid Fibromatosis

  • Long fascicles of spindle and stellate myofibroblasts

  • Vesicular nuclei

  • Small pinpoint nucleoli

  • Fibrillary cytoplasm

  • No cytologic atypia

  • Distinct vascular pattern

    • Small thick-walled and larger thin-walled vessels

  • Prominent collagenous stroma

  • Nuclear β-catenin expression

  • Desmin usually negative

  • Focal and weak expression of actins

  • β-catenin or APC mutations

Nodular Fasciitis

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Spindle Cell Rhabdomyosarcoma

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