Management and outcome of an appendiceal collision tumour composed of neuroendocrine and mucinous neoplasms.

We report an appendiceal collision tumour in a 23-year-old woman who presented with constipation and abdominal fullness. Imaging revealed a right lower quadrant abdominal mass that was laparoscopically resected. Histology revealed an appendiceal collision tumour composed of a low-grade mucinous neoplasm and well-differentiated neuroendocrine neoplasm. A right hemicolectomy for complete oncological control was performed revealing metastatic spread of the neuroendocrine component to the lymph nodes. No further treatment was recommended and the patient was followed with expectant management. At 2-year follow-up, no evidence of disease was found on surveillance imaging. Appendiceal collision tumours can arise in young adults; treatment should be guided by oncological principles of the component tumours. © BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.