To further exclude the possibility of pathological misclassification of endometrioid, clear cell or LGS tumours in the mutation-negative cases, we also tested for mutations commonly associated with these subtypes in KRAS (exon 2), BRAF (exon 15), CTNNB1 (exon 3), and PIK3CA (exons 10 and 21). The gene discussed is CTNNB1; the disease is Lennox-Gastaut syndrome.