A case of a primary anal canal leiomyoma showing abnormal FDG uptake on FDG-PET

Abstract

Leiomyomas arising from the anal canal are rare and so far only one case of the disease has been reported in Japan. Furthermore, FDG-PET-positive leiomyoma in the digestive tract has little been reported. We report a rare case of a leiomyoma arisen in the anal canal showing abnormal FDG uptake on FDG-PET scan.
A 36-year-old woman was admitted to our hospital because of a gradually enlarging anal mass for these three months that had first been noticed 2 years earlier. She complained of frequent defecation and dyschezia. An elastic hard mass 3 centimeter in size was palpated under the anal mucosa and skin. FDG-PET showed abnormal FDG uptake in an area where was identical with the tumor site. We resected the tumor including a part of the internal anal sphincter muscle. The tumor was elastic-hard and 3.5×2.5 cm in size. The pathological diagnosis was leiomyoma originated from the internal anal sphincter muscle.
The anal function was improved and dyschezia disappeared after the operation.