Soft tissue
Skeletal muscle
Rhabdomyosarcoma
Pleomorphic rhabdomyosarcoma
Author: Erdener Özer, M.D., Ph.D.
Editorial Board Member: Michael R. Clay, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Topic Completed: 1 February 2018
Minor changes: 2 December 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Pleomorphic rhabdomyosarcoma[TI]
Table of Contents
Definition / general | Essential features | Epidemiology | Clinical features | Radiology images | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Electron microscopy images | Molecular / cytogenetics description | Differential diagnosis | Additional references | Board review style question #1 | Board review style answer #1Cite this page: Özer, E. Pleomorphic rhabdomyosarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuepleomorphicrhabdo.html. Accessed May 6th, 2021.
Definition / general
- High grade sarcoma composed of undifferentiated cells (Fletcher: WHO Classification of Tumours of Soft Tissue and Bone, 4th Edition, 2013)
- Exceedingly rare category of rhabdomyosarcoma (RMS) in adults
- Not well characterized in the pediatric population; many of these cases can be considered RMS with diffuse anaplasia
Essential features
- High grade sarcoma composed of atypical cells that display skeletal muscle differentiation
- No embryonal or alveolar component of rhabdomyosarcoma
Epidemiology
- Usually older than 50
- 70% male
Clinical features
- Rapidly growing, painful mass, most commonly of lower extremity
Radiology images
Contributed by Erdener Özer, M.D., Ph.D.
MRI
Images hosted on other servers:
MRI
Case reports
- 28 year old man with pleomorphic RMS of thigh (Oncol Lett 2016;12:1921)
- 50 year old man with pleomorphic RMS in subcutaneous tissue of trunk (J Dermatol 2017;44:59)
- 73 year old woman with pleomorphic RMS of uterus (Anticancer Res 2017;37:2509)
Treatment
- Clinical behavior and responsiveness to chemotherapy are similar to adult high grade soft tissue sarcomas
- Poor prognosis; 70% die of disease after mean follow up of 20 months (Mod Pathol 2001;14:595)
Gross description
- Mean 7 cm, up to 30 cm
- White firm cut surface with variable hemorrhage and necrosis
- May be confined to fascial compartment and assume shape of muscle from which it arises
Gross images
Contributed by Debra Zynger, M.D.
Thigh mass
Images hosted on other servers:
Paratesticular tumors
Resected tumor
Microscopic (histologic) description
- Sheets of large, atypical and frequently multinucleated polygonal eosinophilic cells
- Sometimes undifferentiated round to spindle cells
- Cross striations are seldom detected
Microscopic (histologic) images
Contributed by Burcin Tuna, M.D.
H&E, x10
H&E, x20
Desmin, x10
MyoD1, x20
AFIP images
Fascicular pattern
Storiform pattern
Patternless pattern
Hemangioperi-cytoma-like pattern
Spindle cells
Pleomorphic and polygonal cells
Epithelioid cells with abundant eosinophilic cytoplasm
Clear cytoplasm due to washing out of glycogen
Positive stains
Negative stains
Electron microscopy description
- Skeletal muscle differentiation with rudimentary sarcomeres containing Z bands or Z band material with thick and thin filaments
Electron microscopy images
Contributed by Mark R. Wick, M.D.
Molecular / cytogenetics description
- Complex karyotype (Cancer Genet Cytogenet 2009;192:1)
- Comparative genomic in situ hybridization (CGH) reveals eight highly amplified regions at 1p36.1-p36.2, 1p31-p32, 1q21-q31, 8q12-q21, 8q24-qter, 11q12-q13, 12q13-q14 and 18q12-q22 (Am J Cancer Res 2012;2:141)
Differential diagnosis
- Embryonal or alveolar rhabdomyosarcoma with anaplastic features: no evidence of embryonal or alveolar component
- Undifferentiated pleomorphic sarcoma - pleomorphic: diagnosis of exclusion, no evidence of skeletal muscle differentiation
- Pleomorphic liposarcoma: no evidence of skeletal muscle differentiation
- Sarcomas such as malignant mixed Müllerian tumor and dedifferentiated liposarcoma due to presence of heterologous rhabdomyosarcomatous differentiation: diagnosis of exclusion of primary tumor
Additional references
Board review style question #1
Which of the following is true for pleomorphic rhabdomyosarcoma?
- Are usually tumors of children
- Composed of an embryonal component
- Copy number pattern seen differs from alveolar rhabdomyosarcoma
- May express pankeratin
- Tumor cells often display cross striations
Board review style answer #1
C. Copy number pattern seen differs from alveolar rhabdomyosarcoma
