Collision tumor at the rectum consisting of a neuroendocrine carcinoma and adenocarcinoma: A case report

INTRODUCTION AND IMPORTANCE: Neuroendocrine carcinoma of the colon and rectum account for less than 1% of all colorectal malignancies. Here we report a case of a collision tumor at the rectum consisting of a neuroendocrine carcinoma and adenocarcinoma. CASE PRESENTATION: A 46-year-old asymptomatic female with severe anemia was referred by her primary care physician for admission. Initial imaging showed several innumerable heterogenous hypodense lesions within the liver. Following a colonoscopy and the excision of a rectal mass, the histopathology report revealed a Collision tumor. CLINICAL DISCUSSION: There are no specific clinical features or imaging findings. The diagnosis is made post operatively dependent on histopathology. CONCLUSION: It is essential to report these cases to advance a further understanding of the behaviour of these tumors, in addition to develop evidence-based guidelines and treatment strategies.