Imaging Diagnosis of Perianal Leiomyoma: A Case Report.

A leiomyoma is a benign mesenchymal neoplasm that usually develops where smooth muscle is present. In this report, we present the case of a 75-year-old woman who sought medical attention due to pelvic organ prolapse and urinary incontinence, and without defecatory symptoms. Both pelvic floor ultrasound and magnetic resonance imaging (MRI) examination showed a well-defined mass in the ischioanal fossa, eventually diagnosed as a perianal leiomyoma. It is considered a rare entity because of its location involving the anal sphincter and clinical features. We describe the ultrasonographic and MRI findings of this perianal leiomyoma, together with differential diagnoses and immunohistochemical characterization.