A malignant mesenchymal neoplasm that arises from the vagina. Representative examples include botryoid-type embryonal rhabdomyosarcoma, leiomyosarcoma, and endometrioid stromal sarcoma. The disease is vagina sarcoma (Monarch Disease Ontology id MONDO_0002140). Also known as: sarcoma of the vagina, sarcoma of vagina, vaginal sarcoma.