IDH1 (encoding isocitrate dehydrogenase 1) and IDH2 (encoding isocitrate dehydrogenase 2) mutations are frequently (~50%) present in conventional central chondrosarcoma,6, 7 whereas clear cell chondrosarcomas lack IDH1 and IDH2 mutations (n = 17),8, 9 although a H3F3B (encoding H3 histone family member 3B) p.K36M mutation was found in one case.10 Here, we describe the clinicopathological features of five cases of chondrosarcoma with morphological features of conventional chondrosarcoma alongside areas of classic clear cell chondrosarcoma encountered in a bone tumour consultation practice. The gene discussed is IDH1; the disease is clear cell chondrosarcoma.