Through the re-sequencing of REEP5 in 23 sporadic AMTs and/or PMP cases, we did not identify any germline REEP5 mutations, despite a shared LoF variant found in our family, and the loss of REEP5 in a case report of a patient with FAP and an appendiceal mucinous tumour. Here, REEP5 is linked to mucinous neoplasm.