The patient proceeded to resection of the mass.
Histopathology
MACROSCOPIC DESCRIPTION: "Tumour pelvic": An irregular shaped tissue mass with a ragged external surface, 57x47x31mm. The external surface is inked blue. The cut surface is solid and cystic areas with a variegated appearance.
MICROSCOPIC DESCRIPTION: The sections show a multicystic lesion lined by a variety of epithelial types including stratified squamous, respiratory type, mucinous columnar and bland cuboidal. Some of the spaces are surrounded by plasma cell rich and xanthomatous inflammation. Mature fat, skeletal muscle and areas of haemorrhage are also present. There is no evidence of malignancy.
DIAGNOSIS: Tailgut duplication cyst (retrorectal cystic hamartoma).