INTRODUCTION: The phosphatase and tensin homolog hamartoma tumor syndrome (PHTS) refers to a spectrum of disorders caused by variants of the phosphatase and tensin homolog ( CASE PRESENTATION: We describe the case of a 44-year-old female patient with invasive ductal carcinoma of the right breast. Cobblestone papillomatosis was present in the gingiva. She had a medical history of bilateral adenomatous goiters for 10 years. Her mother had been diagnosed with breast cancer, thyroid and tongue tumors, gastric polyps, hepatic hemangioma, and collagen disease. Additionally, the patient's maternal grandmother had a history of colon cancer. Based on the patient's family history and physical findings, CS was suspected, and direct DNA sequencing analysis revealed a haplotype c.634del mutation in exon 7 of the CONCLUSIONS: We report a case of breast cancer with a newly diagnosed c.634del mutation in the