Soft tissue

Skeletal muscle

Rhabdomyosarcoma

Spindle cell / sclerosing 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 May 2018

Minor changes: 23 July 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Sclerosing rhabdomyosarcoma

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Table of Contents

Cite this page: Özer E. Spindle cell / sclerosing rhabdomyosarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuesclerosingrhabdo.html. Accessed October 21st, 2021.

Definition / general

Spindle cell / sclerosing rhabdomyosarcoma (RMS) is a rare variant
Spindle cell pattern was proposed in 1992 by Cavazzana et al. and the sclerosing pattern was described in 2000 by Mentzel and Katenkamp (Am J Surg Pathol 1992;16:229, Virchows Arch 2000;436:305)
Predilection for the head and neck / extremities
5 - 10% of RMS (IARC: WHO Classification of Tumours of Soft Tissue and Bone, 4th edition, 2013, Arch Pathol Lab Med 2015;139:1281)

Essential features

Variant of rhabdomyosarcoma with dense hyalinizing collagenous matrix with rounded or spindle shaped tumor cells arranged in small nests present in at least 80% of the tumor (Am J Surg Pathol 2002;26:1175, Am J Clin Pathol 2008;129:410)

Terminology

Spindle cell / sclerosing are considered the same diagnostic variant of rhabdomyosarcoma
Previously categorized as a part of embryonal rhabdomyosarcoma

Clinical features

Sclerosing: more common in adults in the extremities and head and neck region (Am J Surg Pathol 2002;26:1175)
Spindle cell: most common in the paratestis, followed by head and neck
More common in the pediatric population in the extremities (Arch Pathol Lab Med 2015;139:1281)
Males > females

Radiology images

Images hosted on other servers:

Large masticator space mass in neck

Cranial MRI

CT scan

MRI

Prognostic factors

In adults, recurrence and metastasis rate of 40 - 50% (Arch Pathol Lab Med 2015;139:1281)
In pediatric population, similar behavior to embryonal variant except parameningeal spindle cell is more aggressive (Arch Pathol Lab Med 2015;139:1281)
Prognosis of tumors in the head and neck is worse than those located in the extremities

Case reports

24 year old man with skull tumor (Int J Clin Exp Pathol 2015;8:2205)
26 year old woman with a large chest wall tumor (Ann Thorac Cardiovasc Surg 2014;20:642)
32 year old man with swelling of right masseter (Case of the Week #457)
35 year old man presenting with knee tumor (Indian J Pathol Microbiol 2015;58:335)
36 year old Latino man with parotid gland tumor (Head Neck Pathol 2015;9:147)
50 year old man with oral rhabdomyosarcoma (Indian J Otolaryngol Head Neck Surg 2016;68:384)
55 year old woman with a right thigh mass (Diagn Cytopathol 2010;38:761)
67 year old Japanese woman with tumor in the masticator space (Acta Radiol Open 2017;6:2058460117727316)

Treatment

No consensus for optimal treatment
Mainstay therapeutic method should be similar to most soft tissue tumors including surgery and adjuvant chemotherapy or radiotherapy can be added (Int J Clin Exp Pathol 2015;8:13814)

Clinical images

Images hosted on other servers:

Cystic mass 10 × 10 × 8 cm

Gross description

Poorly circumscribed, fleshy, expanding masses

Microscopic (histologic) description

Neoplastic cells are arranged in lobules, small nests, microalveoli and single file arrays in an abundant hyalinized, eosinophilic to basophilic matrix that closely resembles primitive osteoid or chondroid material
Mitotic rate is very high (> 20 mitotic figures / 20 high power fields)
Spindle cells or small primitive-like cells embedded in abundant in collagen stroma
Scattered rhabdomyoblasts with eccentric nuclei and significant ample eosinophilic cytoplasm
In some cases tumor cells focally display a cribriform pattern closely mimicking adenoid cystic carcinoma

Microscopic (histologic) images

Contributed by Dr. Saroona Haroon, Case #457

x10

x20

x40

CD34

Desmin

S100

MSA

MyoD1

Myogenin

Myoglobin

Images hosted on other servers:

Hyalinizing collagenous matrix

Neoplastic cells arranged into microalveoli

Neoplastic cells arranged into lobules

Hyalinized matrix resembles osteoid

IHC positivity to desmin, myogenin, SMA, MyoD1

Spindle cell and sclerosing features

Uniformly distributed tumor cells

H&E, desmin, myogenin

Cytology images

Images hosted on other servers:

Fine needle aspiration

Positive stains

Strongly positive for MyoD1 (diffuse) and vimentin (diffuse)
Desmin (focal) and weak / focal positive for myogenin and actin
Some cases can also show positive expression of CD99, SMA and CD56

Negative stains

Cytokeratin, S100, CD34 and CD31

Electron microscopy description

Irregularly distributed disorganized filament in richly collagenized matrix
No Z bands

Molecular / cytogenetics description

Should be PAX fusion negative
Recurrent MyoD1 mutations (Genes Chromosomes Cancer 2014;53:779)
Specific MDM2 / HMGA2 amplification at 12q13 - 15 (Hum Pathol 2009;40:1347)
Loss of 10q22, loss of chromosome Y and gain of 18 (Virchows Arch 2006;449:572)
Pattern of numerical changes similar to embryonal rhabdomyosarcoma in one case (Virchows Arch 2005;446:64)
In an adult case: gain of chromosome 11 and loss of chromosome 22 (Virchows Arch 2005;446:64)
Cytogenetic findings in 2 pediatric cases suggest a link with embryonal rhabdomyosarcoma (Int J Surg Pathol 2006;14:193)

Differential diagnosis

Alveolar rhabdomyosarcoma (RMS): different morphology; has PAX3 and PAX7-FKHR fusion transcripts (Pediatr Dev Pathol 2004;7:583) and myogenin is generally seen as weak, focal and nuclear
Angiosarcoma: lacks characteristic hyalinizing matrix of sclerosing RMS, is negative for desmin, myogenin and MyoD1, but is CD31 and CD34 positive (Head Neck Pathol 2015;9:147)
Extraskeletal myxoid chondrosarcoma: typically forms a well circumscribed, multilobulated architecture separated by incomplete fibrous septa with round or slightly elongated cells of uniform shape and size usually arranged in short anastomosing strands or cords in myxoid matrix
Mesenchymal chondrosarcoma: characterized by distinct undifferentiated tumor cells admixed with well differentiated cartilagenous components
Metastatic carcinoma: positive expression of cytokeratin is seen in metastatic carcinoma, whereas desmin and MyoD1 are negative
Osteosarcoma: has neoplastic osteoid, matrix calcification, osteoclasts
Parachordoma: typically lobulated and contains nests of vacuolated cells deposited in a myxoid matrix, resembling the physaliphorous cells of chordoma; expresses S100 protein and cytokeratin
Sclerosing epithelioid fibrosarcoma: composed of epithelioid cells arranged in nests and cords and deposited in a densely hyalinized collagenous matrix; however, in almost all cases the tumor also shows foci of spindle shaped sarcoma similar to conventional fibrosarcoma and exhibits EMA or MUC4 positivity (Head Neck Pathol 2015;9:147)
Also synovial sarcoma, leiomyosarcoma, spindle cell carcinoma, spindle cell melanoma, fibrosarcoma, malignant peripheral nerve sheath tumor, and malignant triton tumor

Additional references

Anticancer Res 2015;35:6213, CAP: Protocol for the Examination of Specimens From Patients With Rhabdomyosarcoma [Accessed 25 April 2018]

Board review style question #1

Actin
CD99
Desmin
MyoD1
Myogenin

Board review style answer #1

D. MyoD1

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Reference: Spindle cell / sclerosing rhabdomyosarcoma

Board review style question #2

Which of the following is associated with sclerosing rhabdomyosarcoma?

A. PAX7-FOXO1A fusion
B. Polypoid growth with a cambium layer
C. Arises only in adults over 45
D. Pseudovascular growth pattern

Board review style answer #2

D. Sclerosing rhabdomyosarcomas often display a pseudovascular growth pattern. PAX7-FOXO1A fusion is associated with the alveolar subtype; polypoid growth with a cambium layer is seen in the botryoid type; and the pleomorphic subtype is seen in older patients.

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Reference: Spindle cell / sclerosing rhabdomyosarcoma