Rhabdomyosarcoma of the female genital tract: Long-term outcome and association with DICER1 variation.

Abstract

10538 Background: Rhabdomyosarcoma (RMS) of the female genital tract is rare, accounting for 3.5% of cases of rhabdomyosarcomas. Germline DICER1 mutations are associated with predisposition to pleuropulmonary blastoma and other tumors including sarcomas. Recently DICER1-associated RMS of the uterus/ovary has ben reported.. The aim of this study is to evaluate demographic characteristics, molecular pathogenesis, treatment and long term outcome of female genital tract rhabdomyosarcoma. Methods: Files of children with RMS of the female genital tract diagnosed at the Istanbul University, Oncology Institute during 1990-2019 were reviewed. Molecular genetic sequencing was performed by polymerase chain reaction amplification of genomic DNA extracted from the formalin-fixed, paraffin embedded tumors, followed by Sanger sequencing. Genetic testing for DICER1 variants of the proband and family members was performed if DICER1 mutation was detected in the tumor of the proband. Results: Of 210 RMS cases, 11 arose from the female genital tract. The median age at diagnosis was 52 months (10 months-15 years). Primary sites were vaginal (n = 5), uterus (n = 4), and ovary(n = 2). Presenting symptoms included vaginal mass (n = 6), vaginal bleeding (n = 5), and abdominal pain (n = 3). Four had group 1, five group 3, two group 2 disease and all received chemotherapy (vincristine, actinomycinD + cyclophosphamide).Three received radiotherapy; three underwent hysterectomy. DICER1 mutation was detected in tumor tissue in three patients:[ c.5113G > A (p.E1705K); c.5428G > T (p.D1810Y); c.1870C > T (p.Arg624Ter)] Genetic testing revealed germline DICER1 pathogenic variation in two patients and their family members, one of whom had cystic nephroma in infancy and history of Wilms tumor in an uncle. They were referred for surveillance for the DICER1 related diseases. A patient with metachronous bilateral ovarian RMS died. Two are married, one has children. The 5 year survival for RMS of the female genital tract was 85.7 % at a median follow-up of 34 (4-298) months. Conclusions: Rhabdomyosarcoma of the female genital tract is associated with a favorable prognosis, however some individuals undergo aggressive local therapies. Individuals with RMS of the female genital tract should be tested for DICER1 pathogenic variation. The detection of a DICER1 mutation in an individual or family members is important to facilitate surveillance for related tumors, so that they may be detected at the earliest possible stage, potentially increasing survival and decreasing risks of late effects.