IPMN, however, shares many similarities with low-grade, papillary-cystic forms of MA, including the identical activating AKT1 p.Glu17Lys (alias p.E17K) gene mutation, and therefore, it was originally proposed as a subtype within the spectrum of low-grade MA in the 5th edition of the WHO Classification of Head and Neck Tumours. This evidence concerns the gene AKT1 and microtia.