Mesenchymal chondrosarcoma

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Mesenchymal chondrosarcoma is a rare type of chondrosarcoma found in the soft tissue.

General

  • Rare variant of chondrosarcoma.
  • 2–10% of primary chondrosarcomas
  • Adolescents and young adults
  • Female predilection
  • Most commonly intraosseous but can occur in extraskeletal sites especially the central nervous system (from the meminges)
  • The 'mesenchymal' in the name refers to the ability to arise in soft tissues.[1]
  • Conceptualized as originating from a pleuripotential mesenchymal cell with foci recapitulating enchondral ossification.
  • The small cells appear to be an undifferentiated cartilage stem cell which “differentiate” into benign cartilage [2].

Gross

Pink and fleshy with foci of calcification.

Microscopic

'White clouds in a dark blue sky'

  • Malignant tumor with a characteristic biphasic pattern
    • Cellular poorly differentiated small round blue cells
    • Can have a hemangiopericytomatous vascular pattern
    • Islands of well-differentiated hyaline cartilage
      • Progressive maturation of cartilage towards the center
      • Central calcification or bone formation

Images

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IHC

  • SOX9 (positive in small cells and chondrocytes).[3]
  • S100 (positive in chondrocytes not in small cells).
  • Osteocalcin (negative in small cells).
  • CD99 - (positive in small cells)

DDX

Depends a bit on where the tumor is located and how much cartilage is readily visible.

    • Hemangiopericytoma - no cartilage
    • Lymphoma - Sox9 negative, CD45 positive
    • Metaplastic Glioblastoma - usually older adults - GFAP positive
    • Chondrosarcoma - usually older adults - hyaline cartilage is malignant
    • Small cell osteosarcoma - Sox10 negative, no cartilage
    • Ewing sarcoma - Both are CD99 positive but ES is Sox9 negative, no cartilage
    • Monophasic synovial sarcoma - also can have the hemangiopericytomatous vasculature

Molecular

t(8;8)(q21.1;q13.3) HEY1-NCOA2.[4]

See also

References

  1. Dowling EA (June 1964). "Mesenchymal chondrosarcoma". J Bone Joint Surg Am 46: 747–54. PMID 14161087. http://www.ejbjs.org/cgi/reprint/46/4/747.pdf.
  2. Fanburg-Smith, JC.; Auerbach, A.; Marwaha, JS.; Wang, Z.; Rushing, EJ. (May 2010). "Reappraisal of mesenchymal chondrosarcoma: novel morphologic observations of the hyaline cartilage and endochondral ossification and beta-catenin, Sox9, and osteocalcin immunostaining of 22 cases.". Hum Pathol 41 (5): 653-62. doi:10.1016/j.humpath.2009.11.006. PMID 20138330.
  3. Pang, ZG.; He, XZ.; Wu, LY.; Wei, W.; Liu, XY.; Liao, DY.; Li, FY.; Zhang, XL. (Jun 2011). "[Clinicopathologic and immunohistochemical study of 23 cases of mesenchymal chondrosarcoma].". Zhonghua Bing Li Xue Za Zhi 40 (6): 368-72. PMID 21914343.
  4. Panagopoulos, I.; Gorunova, L.; Bjerkehagen, B.; Boye, K.; Heim, S. (Jul 2014). "Chromosome aberrations and HEY1-NCOA2 fusion gene in a mesenchymal chondrosarcoma.". Oncol Rep 32 (1): 40-4. doi:10.3892/or.2014.3180. PMID 24839999.