A unique case report of three morphologically distinct malignancies in an appendix specimen

INTRODUCTION AND IMPORTANCE: Appendiceal neoplasms have a diverse histological classification, the commonest type being neuro-endocrine neoplasm and accounting for 60% of all primary appendiceal malignancies. Others include colonic-type adenocarcinoma; mucinous neoplasm, and goblet cell carcinoma. This report describes a unique case of three different histological subtypes of appendiceal malignancy within a single specimen. CASE PRESENTATION: A 65-year-old female presented with symptoms concerning of GI malignancy and underwent computerised tomography pneumocolon showing an abnormally enhancing appendix concerning for an appendiceal tumour. After multidisciplinary team discussion the patient underwent an open right hemicolectomy. Post-operative histological analysis showed complete resection of three distinct tumour subgroups within the specimen: a neuroendocrine tumour; a well-differentiated adenocarcinoma, and a low-grade appendiceal mucinous neoplasm. CLINICAL DISCUSSION: This report describes, to our knowledge, the first documented case of three separate histological malignancies in a single appendix. Appendiceal malignancy is rare and there are less than 10 cases pertaining to the appendix in the literature: all describing dual neuroendocrine tumours and appendiceal mucinous neoplasms. The case also highlights a limitation of colonoscopy in the diagnosis of colorectal malignancy, specifically for appendiceal tumours, and caution must be taken in discharging patients after a negative colonoscopy. A multi-disciplinary approach is of utmost importance in managing these patients. CONCLUSION: This is a rare case of 3 morphologically different neoplasms contained within one appendix and demonstrates the importance of an MDT approach to management of such cases. It also highlights the limitation of colonoscopy in diagnosis of appendiceal malignancy.