Methylome profiling of cartilage tumors: a promising new diagnostic tool?

We evaluated its utility in cartilage tumors, where distinguishing low-grade from high-grade conventional central chondrosarcoma (CS) as well as atypical cartilaginous tumors (ACT) from enchondromas are frequent diagnostic challenges, particularly on biopsy material. We analyzed 214 chondrogenic tumors, including enchondromas, ACT, conventional central, dedifferentiated, and clear cell chondrosarcomas, and determined their IDH1/2 mutation status.

Unsupervised dimensionality reduction of genome-wide DNA methylation patterns revealed four clusters among IDH-mutant tumors (IDH-MUT-1: mostly enchondromas and ACT and some high-grade CS; IDH-MUT-2: predominantly high-grade CS; IDH-MUT-3: largely dedifferentiated CS; IDH-MUT-HN: distinct head and neck group with markedly different methylation pattern) and two clusters among IDH-wildtype tumors (IDH-WT-1 and IDH-WT-2: both primarily high-grade CS, with IDH-WT-2 showing higher tumor grade and more extensive CNVs).