MKI67 and neoplasm: Neuroendocrine carcinomas demonstrate a high proliferation rate, as reflected by a high number of mitoses and a Ki-67 positive fraction of > 20%.[2–4] Colorectal neuroendocrine carcinoma (CRNEC), which originates in the hind gut, is a rare aggressive cancer accounting for less than a percent of all colorectal cancer cases; however, in some studies that included collision tumor, this figure was as high as 3.9%.[5–7] Patients with HGNEC may be asymptomatic and are often detected incidentally during imaging studies, endoscopy of the lower gastrointestinal tract, or biopsy.