Updated: 10/23/2017

Rhabdomyosarcoma

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Introduction
  • A malignant tumor of the primitive mesenchyme
    • it is the most common sarcoma in children 
  • Four sub-types of rhabdomyosarcoma
    • Embryonal
      • occurs in infants and young children
    • Alveolar
      • occurs in adolescents and young adults
    • Botryoid
      • occurs in infants and young children, typically in the vagina
      • aka Sarcoma botryoides or "bunch of grapes"
    • Pleomorphic 
      • tends to occur in older patients 40-70yrs
  • Genetics
    • alveolar rhabdomyosarcoma has a common t(2;13) translocation 
      • forms Pax3-FKHR fusion protein 
      • associated with a high risk metastatic disease 
  • Metastasis
    • nodal metastasis are known to occur with rhabdomyosarcoma
      • consider sentinel lymph node biopsy as part of treatment
    • bone marrow biopsy is required for staging
      • bone marrow metastases have been shown to portend a worse prognosis
  • Prognosis
    • 5-year survival
      • Embryonal - 80%
      • Alveolar - 60%
      • Botryoid - uniformly fatal, less than 30% of patients live 5 years from the time of diagnosis
      • Pleomorphic - 25%
Symptoms
  • Presentation
    • rapidly growing painless mass
    • most lesions occur in the head/neck, genitourinary system, or retroperitoneum
Imaging
  • CT 
    • CT of the chest is required for staging of disease
  • MRI
    • non-diagnostic but crucial for treatment planning
    • rhabdomyosarcoma images appear like many other soft tissue sarcomas
      • dark on T1, bright on T2
Histology
  • Characteristic histology includes
    • Embryonal
      • small round blue cell tumor 
      • skeletal muscle-like cross-striations can occur
      • based on the stage of neoplastic cell development
    • Alveolar post
      • poorly differentiated round cells with multinucleated giant cells
      • cellular aggregates are surrounded by dense fibrous septae 
    • Pleomorphic
      • multiple cell types present
      • difficult to differentiate from other pleomorphic sarcomas
  • Immunohistochemistry
    • MyoD1 positive
    • myoglobin positive 
    • myosin positive
    • desmin positive
    • vimentin positive
Treatment
  • Nonoperative
    • chemotherapy alone
      • indications
        • only indicated in select patients with widespread metastatic disease.
    • radiation therapy alone
      • indications
        • can be used for unresectable tumors or close/positive margins
  • Operative
    • wide surgical excision with chemotherapy
      • indications
        • pediatric rhabdomyosarcoma
        • chemotherapy is not effective for adult rhabdomyosarcoma 
      • technique
        • common agents include vincristine, dactinomycin, cyclophosphamide
    • wide surgical excision with radiation therapy
      • indications
        •  adult pleomorphic rhabdomyosarcoma 
Differentials & Groups
         
Malignant small round blue cell
   
Rhabdomyosarcoma        
   
Neuroblastoma        
   
Lymphoma        
   
Leukemia        
   
Ewing's sarcoma        
   
Metastatic disease        
   
 
 
IBank
  Location
Xray
Xray
CT
B. Scan
MRI
MRI
Histo(1)

Case A

arm, 14 y/o boy
 
 
(1) - histology does not always correspond to case 


 

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Questions (4)

(OBQ07.251) Which of the following statements regarding rhabdomyosarcoma is true? Review Topic

QID: 912
1

Most common soft tissue sarcoma in the foot

4%

(37/904)

2

Most common soft tissue sarcoma in a child

78%

(703/904)

3

Commonly shows calcification on plain radiographs

8%

(70/904)

4

Soft tissue sarcoma associated with Maffucci's syndrome

6%

(55/904)

5

Dedifferentiates from benign myxomatous tumors

4%

(36/904)

ML 2

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PREFERRED RESPONSE 2

(OBQ07.104) The fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is chararcteristically found in which malignancy? Review Topic

QID: 765
1

Synovial sarcoma

79%

(754/952)

2

Chronic myelogenous leukemia (CML)

3%

(25/952)

3

Ewings sarcoma

12%

(112/952)

4

Alveolar rhabdomyosarcoma

3%

(31/952)

5

Clear cell sarcoma

3%

(28/952)

ML 2

Select Answer to see Preferred Response

PREFERRED RESPONSE 1
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