Phosphatase and tensin-homolog deleted on chromosome 10 (PTEN) is an important cancer suppressor gene. Its pathogenic mutation leads to PTEN hamartoma tumor syndrome (PHTS), a rare syndrome also known as Cowden syndrome, which is relevant to early-onset hereditary breast cancer (BC). In this paper, we report three patients with unilateral multicentric BC and synchronous and metachronous bilateral BC who harbored PTEN gene mutations, and summarize the clinical manifestations, pathological characteristics, diagnosis, treatment and follow-up outcomes to provide reference for management of PTEN gene mutation-related BC among the Cowden syndrome population.