Mixed neuroendocrine-non neuroendocrine neoplasm of the colon

Abstract

Mixed neuroendocrine non-neuroendocrine neoplasm (MiNEN) is a rare diagnosis in which neuroendocrine component is combined with a non-neuroendocrine component, each of which is morphologically and immunohistochemically recognisable as a discrete component and constitute ≥30% of the neoplasm. This case study reports two elderly patients with MiNEN in their colon, the first presented with caecal tumour on colonoscopy and the second had an obstructing mass in hepatic flexure region. They underwent hemicolectomy which revealed similar morphological findings which showed high grade adenocarcinoma in the superficial part and poorly differentiated components with signet rings and extracellular mucin in the deeper aspects. Areas of rhabdoid differentiation is also present in the first patient. Grade 3 neuroendocrine component is well defined within the deep aspect and constitute about 30% of the tumour. These components are positive for synaptophysin and focally for chromogranin with high Ki67. Perineural and lymphovascular invasion is identified in both cases along with metastasis to regional lymph nodes. MiNEN has an aggressive biological behaviour, mostly driven by its (often high-grade) neuroendocrine component, and a dismal prognosis. In summary, we are discussing two cases of MiNEN with poorly differentiated mucin secreting adenocarcinoma and grade 3 neuroendocrine tumour. 1.Frizziero M, Chakrabarty B, Nagy B, et al. Mixed neuroendocrine non-neuroendocrine neoplasms: a systematic review of a controversial and underestimated diagnosis. J Clin Med 2020; 9: 273.2.WHO Classification of Tumours Editorial Board. WHO Classification of Tumours: Digestive System Tumours. 5th ed. Lyon: IARC, 2019.3.de Mestier L, Cros J, Neuzillet C, et al. Digestive system mixed neuroendocrine-non-neuroendocrine neoplasms. Neuroendocrinology 2017; 105: 412–25.