Katherine Reid1, Olga Camacho-Vanegas1, Deep Pandya2, Sandra Catalina Camacho1, Rui Fang Qiao3, Tamara Kalir4,5, Maria M. Padron-Rhenals1, Ann-Marie Beddoe4, Peter Dottino4,6,7 and John A. Martignetti1,2,3,4,7 1Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA; 2Rudy L. Ruggles Biomedical Research Institute, Nuvance Health, Danbury, Connecticut 06810, USA; 3Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA; 4Department of Obstetrics/Gynecology and Reproductive Sciences, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA; 5Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA; 6Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, Connecticut 06520, USA; 7MDDx, Inc., Tarrytown, New York 10591, USA Corresponding author: katherine.reidmssm.edu Abstract

Although the progressive histologic steps leading to endometrial cancer (EndoCA), the most common female reproductive tract malignancy, from endometrial hyperplasia are well-established, the molecular changes accompanying this malignant transformation in a single patient have never been described. We had the unique opportunity to investigate the paired histologic and molecular features associated with the 12-yr development of EndoCA in a postmenopausal female who could not undergo hysterectomy and instead underwent progesterone treatment. Using a specially designed 58-gene next-generation sequencing panel, we analyzed a total of 10 sequential biopsy samples collected over this time frame. A total of eight pathogenic/likely pathogenic mutations in seven genes, APC, ARID1A, CTNNB1, CDKN2A, KRAS, PTEN, and TP53, were identified. A PTEN nonsense mutation p.W111* was present in all samples analyzed except histologically normal endometrium. Apart from this PTEN mutation, the only other recurrent mutation was KRAS G12D, which was present in six biopsy samplings, including histologically normal tissue obtained at the patient's first visit but not detectable in the cancer. The PTEN p.W111* mutant allele fractions were lowest in benign, inactive endometrial glands (0.7%), highest in adenocarcinoma (36.9%), and, notably, were always markedly reduced following progesterone treatment. To our knowledge, this report provides the first molecular characterization of EndoCA development in a single patient. A single PTEN mutation was present throughout the 12 years of cancer development. Importantly, and with potential significance toward medical and nonsurgical management of EndoCA, progesterone treatments were consistently noted to markedly decrease PTEN mutant allele fractions to precancerous levels.

Received July 28, 2023. Accepted October 4, 2023.