In the large bowel, GISTs are seen almost exclusively at the anorectal junction.

Importantly, GISTs very rarely metastasize to lymph nodes (<5 %) so the lack of localized lymph node enlargement for a tumor of this size, directs diagnosis away from rectal and prostate cancer.

Presented with Professor Marco Novelli MBChB MSc PhD FRCPath and Dr Hameed Rafiee FRCR, University College London Hospitals.