Picture quiz An evolutionary relic?

An 89 year old woman was admitted to hospital with central abdominal pain and vomiting. Examination showed a tense distended abdomen with right iliac fossa tenderness but no scars, masses, or organomegaly. There was tenderness on digital rectal examination but no blood or mucus. An abdominal radiograph showed features suggestive of distal small bowel obstruction. No free subdiaphragmatic gas was identified on chest radiograph. Initial estimates of full blood count and serum electrolytes were normal. She was kept nil by mouth, rehydrated with intravenous fluids, and given analgesia.

Computed tomography of the abdomen was carried out (fig 1). Subsequent laparotomy revealed a mass in the region of the appendix with adhesions to the terminal ileum, right ovary and uterus. A limited right hemicolectomy and hysterectomy was performed.

The surgical resection specimen contained a mass associated with the appendix (fig 2), and sectioning indicated a tumour centred on the appendix.

Histological