Accuracy of preoperative biopsy in identifying definitive histology in malignant chondroid tumors

The reliability of Core Needle Biopsy (CNB) for the preoperative diagnosis of chondroid tumors and for determining the histological grade of chondrosarcoma (CS) remains debated. The aim of the study was to evaluate the diagnostic accuracy and agreement of CNB in determining the histological grade of CS.

A retrospective study was conducted including all patients who underwent surgical resection for CS at a tertiary research hospital between 2006 and 2023. All the included patients had preoperative histological diagnosis obtained by CNB. All samples were evaluated by experienced musculoskeletal pathologists. The agreement between CNB and definitive histology was assessed using Cohen's Kappa (κ). Statistical analysis was performed using SPSS version 29.

A total of 111 patients with a mean age of 54.5 ± 16 years were included. Overall concordance between CNB and final histology was observed in 53/111 cases, corresponding to a concordace of 48%. Among the 58 discordant cases, 13 (22.4%) showed a discrepancy of two or more histological grades. Based on the biopsy grade, the concordance was 0% (0/4) for chondroma, 46% (29/63) for G1, 41.4% (12/29) for G2, 40% (2/5) for G3, and 100% (10/10) for dedifferentiated tumors (κ = 0.28). Based on anatomical location, it was stratified by hemipelvis (31 cases, κ = 0.3), distal femur (14, κ = 0.5), proximal femur (19, κ = 0.1), proximal humerus (8, κ = 0), scapula (8, κ = 0.6), and proximal tibia (11, κ = 0.18).

This study showed modest agreement between the histological grade obtained by CNB and the definitive postoperative grade in CS. Agreement was higher in dedifferentiated tumors, in central skeletal lesions, and in tumors with soft tissue invasion. Conversely, concordance was particularly poor in G1-G2 CSs and in peripheral lesions, with an increased risk of undergrading.