Mod C. ChandhanayingyongNicholas M. BernthalPiti UngarreevittayaScott D. NelsonSant P. ChawlaArun S. SinghDavid Geffen School of Medicine at UCLAMahidol UniversityKhon Kaen UniversitySarcoma Oncology Center2018-11-232018-11-232015-11-01JNCCN Journal of the National Comprehensive Cancer Network. Vol.13, No.11 (2015), 1310-131415401413154014052-s2.0-84947274776https://repository.li.mahidol.ac.th/handle/20.500.14594/36276© JNCCN-Journal of the National Comprehensive Cancer Network. A 47-year-old woman, initially diagnosed in 1996 with Cowden syndrome (CS), PTEN-mutant bilateral breast cancer, a thyroid nodule, and uterine fibroids, presented to UCLA in 2013 with Ewing sarcoma of the pelvic bone. Her treatment course included mastectomies, hysterectomy/ oophorectomy, and total thyroid resection, and chemotherapy, radiation, and hemipelvectomy for Ewing sarcoma. This case report illustrates the unusual presentation of Ewing sarcoma in a patient with PTEN-mutant CS, the probable underlying molecular pathogenesis, long-term management, and therapeutic considerations.Mahidol UniversityMedicineArticleSCOPUS10.6004/jnccn.2015.0161