1043 Giant Spindle Cell Lipoma of the Perianal Region: A Rare Cause of a Perianal Mass

Abstract Background The anal and perianal region is an anatomically complex region. The differential diagnosis for perianal masses is broad and can represent both benign and malignant lesions. Case Presentation We present the case of a 63-year-old gentleman who presented to the outpatient clinic with a large perianal mass which had been present for one year. The mass was increasing in size and becoming painful. He did not report any alterations in bowel habit, per rectal bleeding or discharge. His past medical history was significant for type 2 diabetes mellitus and hypertension. He reported a 40-pack year smoking history. On examination, there was a pedunculated soft tissue mass arising from the left side of the anal area measuring approximately 12cm in diameter. MRI scan demonstrated a malignant appearing polypoid lesion originating from the left buttock region close to but separate from the internal anal sphincter. He underwent an elective examination under anaesthesia (EUA) and excision of the perianal lesion. The lesion was multilobulate and involving the external anal sphincter, it was excised en bloc via an elliptical incision. Histological assessment revealed a spindle cell lipoma. The patient had an uneventful post-operative recovery and given the histology findings no further adjuvant treatment was considered necessary. Discussion Spindle cell lipomas are rare, benign lesions characterized by a classic triad of mature adipocytes, ropey collagen, and uniform spindled cells. Surgical excision represents the first line treatment. Conclusion Perianal mass lesions can often pose diagnostic challenges and this case highlights the importance of pathological assessment.