carcinoid tumor GARD:0024176 NCIT:C2915 Editor note: In NCIT all carcinoid tumors are grade 1, but the name is sometimes used more broadly in other sources A slow growing neuroendocrine tumor, composed of uniform, round, or polygonal cells having monotonous, centrally located nuclei and small nucleoli, infrequent mitoses, and no necrosis. The tumor may show a variety of patterns, such as solid, trabecular, and acinar. Electron microscopy shows small secretory granules. Immunohistochemical studies reveal NSE, as well as chromogranin immunoreactivity. Malignant histology (cellular pleomorphism, hyperchromatic nuclei, prominent nucleoli, necrosis, and mitoses) can occasionally be seen. Such cases may have an aggressive clinical course. Gastrointestinal tract and lung are common sites of involvement. UMLS:C0007095 SCTID:443492008 carcinoid tumor (disease) neuroendocrine tumour G1 carcinoid tumour (disease) EFO:0004243 NET G1 HP:0100570 carcinoid tumor MONDO:0005369 ICD9:209.60 MESH:D002276 neuroendocrine tumor G1 ICDO:8241/3 ICDO:8240/3 NANDO:2200396 neuroendocrine neoplasm G1 MEDGEN:2838 carcinoid carcinoid tumor (disease) neuroendocrine neoplasm