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Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other
Sclerosing rhabdomyosarcoma
Author: Nat Pernick, M.D, PathologyOutlines.com, Inc.
Revised: 23 July 2009, last major update July 2009
Copyright: (c) 2002-2009, PathologyOutlines.com, Inc.
Definition
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● Rhabdomyosarcoma with extensive hyalinized matrix production
● Not a WHO diagnosis
● First described in 2000 (Virchows Arch 2000;436:305)
Clinical
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● Adults and children (Int J Surg Pathol 2006;14:193)
● Often in head and neck (Laryngoscope 2005;115:48)
Case reports
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● Tumors of forearm, hand, orbit and nasopharynx of 40 year old woman, 50 year old man, 18 year old man and 21 year old man respectively (AJSP 2002;26:1175)
● 62 year old man with leg tumor (Virchows Arch 2006;449:572)
Gross description
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● 4 to 8 cm
Micro description
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● Lobules and infiltrating cords of small round malignant cells embedded in densely hyalinized matrix with chondroid and osteoid-like appearance
● Extensive mitotic activity (>20 mitotic figures/20 high power fields) in 3 of 4 cases
● May have pseudovascular growth pattern
● One case with single focus of rhabdomyoblastic differentiation with strap cells
● May have areas suggestive of spindle cell rhabdomyosarcoma
● No / focal embryonal or alveolar patterns
● No tumor giant cells
● No definite lacunae or matrix calcification present
Micro images
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Various images
Positive stains
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● MyoD1 (100%, almost every cell)
● Desmin (strong in 1 case, focal in 3 of 4 cases)
● Myogenin focal
Negative stains
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● Cytokeratin; S100
Molecular / cytogenetics
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● No t(2;13) of alveolar rhabdomyosarcoma
● Specific MDM2/HMGA2 amplification at 12q13-15 in 1 case (Hum Pathol 2009 May 18 [Epub ahead of print])
● Loss of 10q22, loss of chromosome Y and gain of #18 in one case (Virchows Arch 2006;449:572)
● Pattern of numerical changes similar to embryonal rhabdomyosarcoma in one case (Virchows Arch 2005;446:64)
EM description
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● Irregularly distributed disorganized filament in richly collagenized matrix
● No Z-bands
Differential diagnosis
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● Alveolar rhabdomyosarcoma (has PAX3 and PAX7-FKHR fusion transcripts, Pediatr Dev Pathol 2004;7:583)
● Chondrosarcoma - has neoplastic chondroid cells
● Osteosarcoma - has neoplastic osteoid
● Sclerosing epithelioid fibrosarcoma
Additional references
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● Am J Clin Pathol 2008;129:410
End of Soft Tissue Tumors Part 3 - Muscle, Vascular, Nerve, Other > Sclerosing rhabdomyosarcoma
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