Activating PIK3CA mutations were detected in 1 hidradenocarcinoma (c.1624G>A; p.Glu542Lys) and 2 porocarcinomas (c.1624G>A; p.Glu542Lys and c.1633G>A; p.Glu545Lys). This evidence concerns the gene PIK3CA and hidradenocarcinoma.