A 65-year-old man reports months of deep seated low back and sacral pain worse on sitting. MRI shows a midline destructive lesion of the sacrum extending into the presacral soft tissue. Biopsy shows lobules of cells arranged in cords within abundant pale mucoid matrix; many cells have vacuolated, bubbly cytoplasm and stain positively for brachyury. This tumour arises from remnants of which embryonic structure?

• A Neural crest cells
• B Synovial lining cells
• C Primitive mesenchymal cartilage rests
• D Notochord ✓

Explanation

Chordoma arises from vestigial remnants of the notochord, hence its predilection for the midline axial skeleton, chiefly the sacrococcygeal region and clivus, in older adults. Histology shows physaliferous cells with bubbly vacuolated cytoplasm in a myxoid matrix, and nuclear brachyury expression is the diagnostic immunomarker. Neural crest origin applies to schwannoma and neuroblastoma, and cartilage rests to chondrosarcoma, which lacks brachyury positivity.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.