• Bone and Bones
• Genes, Neoplasm
• IMMUNOHISTOCHEMISTRY

To the editor

In this month’s issue of the Journal, Zhao et al1 have published a clinicopathological analysis of a group of 307 chondroblastomas diagnosed at a single institution in China. The main focus of the publication is to assess the value of the H3K36M antibody in the diagnosis of chondroblastoma. Interestingly, and probably not surprisingly, this antibody performs much more reliably on undecalcified and EDTA-decalcified specimens than on specimens decalcified with hydrochloric acid-based agents. In this study, all 136 undecalcified and EDTA-decalcified samples were immunoreactive for the H3K36M antibody, while only 87% of the hydrochloric acid-decalcified specimens were positive. Nevertheless, these findings support what is already known about chondroblastomas, that the majority harbour mutations in either the H3F3B gene or less commonly the H3F3A gene resulting in a p.Lys36Met that is easily demonstrable by immunohistochemistry, and that the H3K36M antibody is invaluable in distinguishing histologically unusual and radiographically aggressive chondroblastomas from the equally uncommon chondroblastoma-like osteosarcoma, particularly when dealing with small samples.

As a justification for the publication of their large series of tumours, the authors also refer to the fact that in the fifth edition of the WHO Classification of Tumours, Soft Tissue and Bone Tumours,2 chondroblastoma was reclassified as a …