Answer and Discussion of Quiz Set: N-007

1.    Which of the molecular testing can be used to distinguish chondrosarcoma from chordoid meningioma?

A.  BRAF V600E mutation

B.  Isochromosome 17

C.  Deletion of chromosome 1p and 19q

D.  Mutation of isocitrate dehydrogenase 1 and 2 gene (IDH1, IDH2)

E. Mutation or deletion of SMARCB1/INI1

Answer and Discussion: The answer is (D). Although mutation of IDH1 and IDH2 is only found in some chondroid tumor including chondrosarcoma, these test are good adjunct to be used to distinguish chondrosarcoma from chordoma and chordoid meningioma in the brain. Isochromosome 17 is often seen in medulloblastoma. Deletionof chromosome 1p and 19q are present in some oligodendroglioma and anaplastic oligodendroglioma. Mutation of SMARCB1/INI1 is seen in atypical teratoid/rhabdoid tumor. BRAF mutation and fusion are seen in a variety of tumor including melanoma, papillary thyroid carcinoma, pilocytic astrocytoma, pleomorphic xanthoastrocytoma and other tumors.

Further Reading:

Arai M, Nobusawa S, Ikota H, Takemura S, Nakazato Y. Frequent IDH1/2 mutations in intracranial chondrosarcoma: a possible diagnostic clue for its differentiation from chordoma. Brain Tumor Pathol. 2012 Oct;29(4):201-6.

Amary MF, Bacsi K, Maggiani F, Damato S, Halai D, Berisha F, Pollock R, O'Donnell P, Grigoriadis A, Diss T, Eskandarpour M, Presneau N, Hogendoorn PC, Futreal A, Tirabosco R, Flanagan AM. IDH1 and IDH2 mutations are frequent events in central chondrosarcoma and central and periosteal chondromas but not in other mesenchymal tumours. J Pathol. 2011 Jul;224(3):334-43.