Immunohistochemistry, ploidy and next generation sequencing of ameloblastic carcinomas

The histopathologic database of the Department of Oral and Maxillofacial Pathology at the University of Pretoria was searched for cases diagnosed as ameloblastic carcinoma (AC) over a 20-year period. Cases were subdivided into primary and secondary cases of AC. Ameloblastomas (ABs) that transformed into ACs and a control cohort of conventional ABs were also studied for comparative purposes. Experienced Oral and Maxillofacial Pathologists reviewed all cases to confirm the diagnosis according to the latest World Health Organisation (WHO) diagnostic criteria. The original haematoxylin and eosin-stained slides, immunohistochemical (IHC) stains, and the best representative formalin-fixed paraffin-embedded (FFPE) tissue blocks were accessed. IHC analysis, including Ki-67 proliferation index and surrogate stem cell markers SOX2, OCT4, and Glypican-3, was performed on the representative FFPE tissue block according to the manufacturer's instructions. High-resolution flow cytometry was used to analyse all cases to determine ploidy status. Molecular analysis utilising targeted next-generation sequencing (NGS) paired with an integrated sequencer was performed on all cases.