H2L carcinomas showed heterogeneous gene expression profiles of the PI3K-AKT pathway, according to the presence of an activating mutation: mutant H2L carcinomas had similar profiles to those of HER2-negative carcinomas, while non-mutant H2L carcinomas had similar profiles to those of HER2-positive carcinomas. The gene discussed is PIK3CA; the disease is carcinoma.