title: Primary, large extra-axial chordoma in proximal tibia: a rare case report with literature review and diagnostic implications.
abstract: Primary extra-axial chordomas have been rarely documented, especially in the appendicular bones. Until now, nine such cases, objectively confirmed with positive brachyury immunostaining, have been reported. A 42-year-old male presented with pain in his right tibial tuberosity (shin) of 2-3 years duration without any associated swelling. He denied complaints related to any other lesion elsewhere in his body. Plain radiograph of his lower limbs revealed a large, eccentric, well-defined, lytic lesion containing internal septae with a narrow zone of transition and a sclerotic medullary border in the upper metaphysis of his right tibia, associated with a pathological fracture. There was no other lesion identified in his spine on radiographic imaging. Biopsy sections revealed a tumour composed of polygonal cells with moderate to abundant eosinophilic to vacuolated/'bubbly' cytoplasm (physaliphorous cells) arranged in lobules within a conspicuous myxoid matrix. By immunohistochemistry, tumour cells were diffusely positive for pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), CK19, S100P, meso (HBME1) and Brachyury/T. Diagnosis of an a primary extra-axial chordoma was finally rendered. Subsequently, the patient underwent bone grafting from his iliac crest. The present case constitutes as the 11th documented case of an extra-axial, intraosseous chordoma and the 10th such case occurring in the appendicular bones. Literature review of similar cases; their diagnostic mimics along with diagnostic and therapeutic implications of such cases are discussed herewith.
authors.affiliation: Department of Surgical Pathology, Tata Memorial Centre, Mumbai, India.
authors.forename: Bharat
authors.initials: B
authors.lastname: Rekhi
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor; D001706:Biopsy; D002817:Chordoma / Q000175:diagnosis* / Q000473:pathology; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism; D005819:Genetic Markers; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism; D013977:Tibia / Q000473:pathology*; D000098908:Brachyury Protein
chemical_list: D014408:Biomarkers, Tumor; D005326:Fetal Proteins; D005819:Genetic Markers; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein
keywords: Brachyury; extra-axial chordoma; uncommon bone tumours