Soft tissue
Skeletal muscle
Rhabdomyosarcoma
Rhabdomyosarcoma-general
Author: Vijay Shankar, M.D.
Topic Completed: 1 November 2012
Minor changes: 10 September 2020
Copyright: 2002-2020, PathologyOutlines.com, Inc.
PubMed Search: Rhabdomyosarcoma [title] soft tissue
Related topics: Alveolar, embryonal, pleomorphic, sclerosing
Table of Contents
Definition / general | Epidemiology | Sites | Clinical features | Treatment | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Additional referencesCite this page: Shankar V. Rhabdomyosarcoma-general. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissuerhabdomyosarcoma.html. Accessed September 20th, 2020.
Definition / general
- Primitive malignant soft tissue sarcoma with skeletal muscle phenotype by H&E, immunohistochemistry or EM
- Subtypes: alveolar, anaplastic, embryonal, pleomorphic, sclerosing (Mod Pathol 2001;14:506), although mixtures are common
- Note: some alveolar and embryonal tumors have similar gene expression (Am J Pathol 2009;174:550)
Rhabdomyoblast
- Cell of origin for rhabdomyosarcomas
- Eccentric eosinophilic granular cytoplasm rich in thick and thin filaments
- If round and elongate, are called strap cells or tadpole cells
Epidemiology
- Most common soft tissue sarcoma of childhood/adolescence (5 - 8% of solid pediatric tumors, 50% of pediatric soft tissue sarcomas)
- 50% at 0 - 9 years
- Relatively rare in adults, who often have pleomorphic and NOS subtypes
- Slight male predominance (M/F: 1.3:1)
- Head and neck tumor are more often embryonal types
- Extremity tumors more often have alveolar histologic type
- 80% of genitourinary RMS are embryonal type
- Usually > 5 cm at diagnosis
Sites
- Children 2 - 6 years usually have head, neck or GU tumors
- Teenagers usually have paratesticular, trunk or abdominal tumors
- Rarely described in the ovary (Gynecol Oncol 1983;15:325, Int J Gynecol Pathol 1998;17:113)
Clinical features
- Needle biopsies may be sufficient for accurate diagnosis (Pediatr Blood Cancer 2009;53:356)
- Usually aneuploid
Treatment
- International Classification of Rhabdomyosarcoma (Cancer 1995;76:1073)
- Superior prognosis: botryoid, spindle cell
- Intermediate prognosis: embryonal
- Poor prognosis: alveolar, undifferentiated sarcoma
- Adults have poorer 5 year survival (27%) than children (61%, J Clin Oncol 2009;27:3391)
- Poorer overall 5 year survival in hand/foot (33% versus 56% overall) due to marked tendency to spread and inability to completely excise (Pediatr Hematol Oncol 2009;26:321)
- Poorer survival in childhood embryonal (intermediate-risk) tumors if anaplasia is present (Cancer 2008;113:3242)
- Five year survival has increased from periods 1976-1980 to 1996-2000 for rhabdomyosarcoma overall (53% to 62%), embryonal (61% to 73%) and alveolar subtypes (40% to 48%, Cancer 2009;115:4218)
- Pathologists should compare post-treatment to pre-treatment specimens (Am J Clin Pathol 2005;123:75)
Microscopic (histologic) images
Images hosted on other servers:
Various images
Positive stains
- Recommended panel contains myogenin, sarcomeric actin (90%) and desmin (95%)
- Desmin: reliable for solid variant of alveolar rhabdomyosarcoma, tumors with round or strap cell rhabdomyoblasts, also smooth muscle tumors
- Myoglobin: specific, but only found in better differentiated tumors, may be non-specific due to diffusion from adjacent injured skeletal muscle cells
- Myogenin: sensitive and specific, particularly useful for alveolar subtype (Mod Pathol 2000;13:988)
- MyoD1
- Vimentin (not specific)
Negative stains
Electron microscopy description
- Rhabdomyoblasts contain sarcomeres (thick and thin filaments) and Z bands
Additional references
