Mixed adeno-neuroendocrine carcinoma of the colon (MANEC), a case report ; clinico-pathological features and review. F. Cherbanyk , M. Dimitrief, F. Barros, E. Pezzetta, O. Martinet Service de Chirurgie Hôpital RIVIERA-CHABLAIS site Montreux Introduction : when investigating and operating on colonic tumors one may expect to find, currently and frequently, an adenocarcinoma and sometimes a neuroendocrine tumor, but from time to time a combination of both tumor type (MANEC) may be encoutered. This, obviously, may give additional diagnostic and therapeutic trouble  Methods : we wish to show and illustrate a clinical case in this respect and furthermore to present an overview on this particular subject   Case presentation: a 57 year old-man presented to our emergency room complainig of intense and progressive diffuse abdominal pain with long standing alternating bowel habits and a massive loss of weight.On clinical examination the abdomen was very distended with diffuse pain, guarding and a tender mass in right lower quadrant . A Ct Scan confirmed a tumor of the caecum with signs of peritoneal and omental carcinomatosis, multiple liver metastases and a small amount of free air. An exploratory laparotomy was performed with confirmation of a perforated tumor of the proximal right colon with huge infiltration of the greater omentum and carcinosis. A rigth colectomy with en bloc omentectomy was performed , the post operative course was progressively favorable with full recovery. The anatomopathological examination of the cecal mass astonishingly showed a poorly differentiated to undifferentated mixed adeno-neuroendocrine carcinoma of 8.0 cm of with mutiple nodal metastases and diffuse peritoneal carcinomatosis, staged as pT4a N2b M1.   The EXOCRINE component showing undifferentiated tubulo-glandular structures with mucin secretion and inflammatory infiltration, pancytokeratin + ADENO NEURO The NEURO-ENDOCRINE component with cords and islands of monomorphic cells with large fusiform nuclei and multiple mitotic figures; CDX2, synaptophysin & chromo- granin + Conclusions : Mixed adeno-neuroendocrine carcinoma of the colon (MANEC) are rare heterogeneous composite tumors with bipartite differentation that can origin throughout the whole digestive tract and account for less than 5% of colorectal malignancies. First observed in 1924, these specific forms have been progressively recognized as a separate entity with a wide possible spectrum of combination between a neuro-endocrine and an exocrine component. High grade , intermediate grade and low grade mixed neoplasia have been identified .The tumors may origin from simultaneous proliferation of different cell lineages or from the proliferation of stem cells differentiating along multiple cell lineages. Optimal treatment is still unknown, nevertheless the more aggressive component of MANEC should be mainly considered to establish and guide treatment