PIK3CA and thymoma: Previously reported mutations mostly consist of missense mutations in PIK3R2, which encodes a regulatory subunit of PI3K.24 Activation of PI3K may also be related to the overexpression of a large microRNA cluster on chromosome 19 in type A and AB thymomas.25 PI3K targeting may then be an effective strategy in the treatment of thymic malignancies; a phase II study with buparlisib is currently ongoing (clinicaltrials.gov ID NCT02220855) (Fig. 3).