Soft tissue
Uncertain differentiation
Extraskeletal myxoid chondrosarcoma


Topic Completed: 3 November 2020

Minor changes: 3 November 2020

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PubMed Search: Extraskeletal myxoid chondrosarcoma[TI] free full text[SB]

See Also: Extraskeletal chondrosarcoma, Mesenchymal chondrosarcoma

Borislav A. Alexiev, M.D.
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Cite this page: Alexiev BA. Extraskeletal myxoid chondrosarcoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissueeskchondrosarcomamyxoid.html. Accessed November 27th, 2020.
Definition / general
  • Extraskeletal myxoid chondrosarcoma (EMC) is a malignant mesenchymal neoplasm of uncertain differentiation with abundant myxoid matrix, multilobular architecture, uniform cells arranged in cords, clusters and reticular networks and NR4A3 rearrangement
Essential features
  • Bland cells with eosinophilic cytoplasm and round to oval nuclei with evenly distributed chromatin and inconspicuous nucleolus
  • Tumor cells are characteristically interconnected with one another to form cords and small clusters and complex trabecular or cribriform arrays
  • Despite the name, there is no evidence of cartilaginous differentiation
  • NR4A3 rearrangement
Terminology
  • NR4A3 rearranged myxoid sarcoma (provisional)
ICD coding
  • ICD-O: 9231/3 - Extraskeletal myxoid chondrosarcoma
  • ICD-11: 2B5F.2 & XH9344 - Sarcoma, not elsewhere classified of other specific sites and myxoid chondrosarcoma
Epidemiology
Sites
Pathophysiology
Etiology
  • Unknown
Clinical features
Diagnosis
Radiology description
Radiology images

Contributed by Borislav A. Alexiev, M.D.
MRI of soft tissue mass

MRI of soft tissue mass

Prognostic factors
Case reports
Treatment
  • Standard treatment for localized disease is surgery, plus or minus radiation therapy with an expected prolonged survival, even though the risk of relapse is about 50% (Cancers (Basel) 2020;12:2703)
  • In advanced cases, besides the standard chemotherapy currently used for soft tissue sarcoma, antiangiogenic agents have recently shown promising activity (Cancers (Basel) 2020;12:2703)
Gross description
  • Well demarcated, lobulated (Cancer 1998;83:1504)
  • Myxoid nodules separated by fibrous septa
  • Cystic areas with hemorrhages
Gross images

Contributed by Borislav A. Alexiev, M.D.
Soft tissue mass

Soft tissue mass

Frozen section description
  • Uniform cells with round or spindled shaped nuclei and eosinophilic cytoplasm arranged in cords or clusters within abundant myxoid matrix
Microscopic (histologic) description
  • Multinodular architecture (Cancer 1998;83:1504)
  • Fibrous septa divide the tumor in pools of abundant myxoid or chondromyxoid matrix containing tumor cells (Cancer 1998;83:1504, Pathol Int 2005;55:453)
  • Uniform cells with eosinophilic to vacuolated cytoplasm, often with long delicate cytoplasmic processes and round to oval nuclei with evenly distributed chromatin and inconspicuous nucleolus (Am J Surg Pathol 1999;23:636)
  • Tumor cells are characteristically interconnected with one another to form cords, small clusters and complex trabecular or cribriform arrays
  • Spindle cell differentiation is common
  • Mitotic activity is low
  • Stroma is hypovascular
  • Foci of intralesional hemorrhages are frequently seen in various proportions (Cancer 1998;83:1504)
  • Usually lacks discernible cartilaginous histology (Pathol Int 2005;55:453)
  • 80% of EMCs with variant (non-EWSR1) NR4A3 gene fusions (TAF15, TCF12) demonstrate high grade morphology with increased cellularity, proliferation and cytologic atypia, showing epithelioid / rhabdoid features in half of the cases (Hum Pathol 2014;45:1084)
Microscopic (histologic) images

Contributed by Borislav A. Alexiev, M.D.
Lobular architecture

Lobular architecture

Intralesional hemorrhage

Intralesional hemorrhage

Spindle cell differentiation

Spindle cell differentiation

Cohesive clusters

Cohesive clusters

Low grade nuclei

Low grade nuclei


NSE

NSE

AE1 / AE3

AE1 / AE3

Cytology description
Cytology images

Images hosted on other servers:

Thigh tumor

Negative stains
Electron microscopy description
Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on other servers:
EWSR1 and NR4A3 FISH

EWSR1 and NR4A3 FISH

Sample pathology report
  • Left thigh, excision:
    • Extraskeletal myxoid chondrosarcoma (see comment and synoptic report)
    • Comment: The tumor has a multinodular architecture. Thick fibrous bands separate pools of myxoid stroma containing uniform tumor cells with eosinophilic or vacuolated cytoplasm and round to oval nuclei with evenly distributed chromatin and inconspicuous nucleolus. The cells are interconnected with one another to form cords and small clusters. Foci of intralesional hemorrhages are frequently seen. Mitotic activity is low (1 mitosis/10 high power fields). Immunohistochemically, the tumor cells are positive for NSE and negative for SMA, desmin, GFAP, CD34, S100, AE1 / AE3 and EMA. FISH studies demonstrate rearrangements of NR4AE at 9q22.33 and EWSR1 at 22q12 gene regions. The findings strongly support the diagnosis of extraskeletal myxoid chondrosarcoma. Although often associated with prolonged survival, extraskeletal myxoid chondrosarcoma has high rates of distant recurrence.
Differential diagnosis
Board review style question #1

The most common gene rearranged in extraskeletal myxoid chondrosarcoma is

  1. FOS
  2. NR4A3
  3. PHF1
  4. SS18
  5. ZNF444
Board review answer #1
Board review style question #2

A 50 year old man presented with a left thigh mass. Hematoxylin eosin stains demonstrated hypocellular lobules with abundant pale blue myxoid matrix containing interconnecting cords and clusters of uniform cells with round to ovoid nuclei and eosinophilic or vacuolated cytoplasm. Foci of intralesional hemorrhages were seen. Occasional mitotic figures were identified (2 mitoses/10 high power fields). Immunohistochemical stain for NSE was positive in tumor cells while all of the following were negative: S100, GFAP, AE1 / AE3, desmin, CD34, ERG and h-caldesmon. FISH studies demonstrated rearrangement of the NR4AE gene at 9q22.33.

Which of the following is most likely the correct diagnosis?

  1. Epithelioid sarcoma
  2. Extraskeletal myxoid chondrosarcoma
  3. Metastatic carcinoma
  4. Myoepithelioma
  5. Ossifying fibromyxoid tumor
Board review answer #2
B. Extraskeletal myxoid chondrosarcoma

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Reference: Extraskeletal myxoid chondrosarcoma
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