Objective: Chordoma is a rare tumor with an unpredictable behaviour, and can display malignant behavior because of its tendency to local invasion and recurrence. We searched the prognostic value of histologic features, growth pattern, localization and Ki-67 proliferation index to predict disease-free survival.

Material and Method: Twenty-nine cases diagnosed in a single center were included in the study and evaluated with their 81 surgical specimens, (29 primary tumors, 47 recurrent lesions and five metastatic foci) regarding their matrix formation (myxoid, chondroid), cellular features, (pleomorphism, necrosis, inflammatory infiltration), patterns of proliferation (solid, trabecular, mixed) and Ki-67 proliferation indices.

Results: Eleven of the cases were females (37.9%) while 18 of them were males (62.1%) with a mean age of 54.1±14.6 (ranged between age 23-78 years). Thirty-eight percent of tumors were located in sacrococcigeal region followed by skull base and vertebrae (31% for both). Skull base chordomas which occured in younger patients (p=0.048) showed more trabecular pattern (p=0.04), chondroid matrix (p=0.063), lower Ki-67 (p=0.146) and longer disease-free survival (p=0.021). In contrast, tumors located in vertebrae, showed more “atypical” morphology with solid pattern, nuclear pleomorphism and dedifferentiation, higher Ki-67 indices and shorter disease-free survivals (p=0.021). Sacral tumors were the “intermediate group” which occurred in older patients, and demonstrated average Ki-67 proliferation indices and disease-free survivals.

Conclusion: Vertebral localization, probably in relation with both histologic features and failure of surgery, appeared as a significant risk factor for recurrence and Ki-67 proliferation index retained its potential to predict disease-free survival.