PIK3CA and Lennox-Gastaut syndrome: 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).