PTEN Awareness Day, also known as PTEN Hamartoma Tumor Syndrome Awareness Day, is observed worldwide every October 23. The day was created to educate the public about mutations in the PTEN gene, which can lead to various tumors and are associated with PTEN hamartoma tumor syndromes (PHTS). PHTS encompasses several genetic conditions characterized by benign tumors called hamartomas, which can lead to multiple health issues and an increased risk of several major cancers. Individuals with PTEN mutations may also experience autism spectrum disorders and related developmental challenges. The observance emphasizes the importance of early diagnosis, ongoing research for effective treatments, and the need for lifelong cancer surveillance for affected individuals.