Summary

A 78-year-old man presented to the accident and emergency department with acute abdominal pain. A CT scan done to investigate the pain showed an intra-abdominal abscess medial to the caecum and an incidental exophytic lesion in the gall bladder. This was excised during surgery and sent for histological examination. Histology showed a ciliated foregut cyst of the gall bladder. A literature review revealed that this was the 13th case worldwide, as ciliated foregut cysts are usually found either above the diaphragm or in the liver. It was also the largest cyst described, with 45 mm diameter. So far none of these cysts found in the gall bladder have shown malignant transformation, though those found in the liver have been known to become malignant. Due to histological similarity, excision of ciliated foregut cysts of the gall bladder should be considered as there is still a risk of malignant transformation.