Aggressive angiomyxoma (AA) is a mesenchymal tumour occurring in connective tissue of the perineum or lower pelvis with a marked tendency to local recurrence but which usually does not metastasize. Only 130 cases had been reported to date. We report the case of a 58-year-old woman, presenting with a pelvi-perineal mass, which was considered to be an anal abscess. After surgical excision, an AA was diagnosed, with classical histological features (myxoid and vascular components) and which was positive for vimentin and CD34. This case report shows that clinical diagnosis of AA is difficult and that delayed diagnosis can prevent optimal treatment of these tumors.