Molecular and Immunohistochemical Characteristics of Primary Vaginal Leiomyosarcoma: Case Report and Review of the Literature.

Primary vaginal leiomyosarcoma is a rare malignancy characterized by similar histologic features as uterine leiomyosarcomas. Previous studies of uterine leiomyosarcomas have shown specific molecular alterations, including frequent alterations in TP53, RB1, ATRX, PTEN, MED12, CDKN2A, and MDM2. Similar alterations have been found in primary vaginal leiomyosarcomas as well as an alternative tumorigenic pathway associated with HPV. Herein, we describe a primary vaginal leiomyosarcoma in a 46-yr-old patient. The tumor was located in the vaginal wall without involvement of the uterus or cervix. Morphologically, it was composed of atypical, spindled cells, with a mitotic rate of 25 mitotic figures per 10 high-power fields and tumor type necrosis. Immunohistochemistry showed positivity for h-caldesmon, SMA, desmin, and ER, along with p53 null pattern expression and loss of ATRX and Rb. Next-generation sequencing analysis revealed mutations in ATRX and PTEN, along with homozygous deletions of RB1, and deep deletions in TP53 and NCOR1 tumor suppressor genes. High-risk human papillomavirus (HR-HPV) E6/E7 mRNA in situ hybridization was performed and showed no staining.