[Analysis on clinical characteristics of rectal neuroendocrine tumors]

To analyze the clinicopathological characteristics of rectal neuroendocrine tumors (NETs) so as to improve their understanding and diagnosis.

The data of 62 rectal NETs patients were retrospectively analyzed to summarize their clinical characteristics. They were categorized into 3 types based on the level of histological differentiation. And the relationship of tumor size, histological type and metastases was examined.

The clinical presentations of rectal NETs were atypical. The main clinical presentation was change in bowel habit (n=43, 69.4%); Ten cases (16.1%) were asymptomatic. Nine cases were found during routine digital rectal examination. In 57 cases (91.9%), the distance was within 8 cm from anorectal line. All patients had single lesion without the presence of carcinoid syndrome. 25.8% (16/62) had colonic polyps while 16.1% (10/62) synchronous colorectal adenocarcinomas. Except for synchronous colorectal adenocarcinomas (n=10), among 52 cases, there were 39 cases with tumor diameter <1 cm, the main type was type I; 7 cases with tumor diameter >2 cm, the main types were types II and III. The metastatic rates in three groups with tumor diameter <1 cm, 1-2 cm and >2 cm were 0, 33.3% and 71.4% respectively.

The clinical presentations of rectal NETs are non-specific. Most cases are often single lesion without the presence of carcinoid syndrome. The clinical process and prognosis of rectal NETs are closely related to tumor size, histological type, the presence of lymph node metastases and liver metastases. The routine digital rectal examination is the simplest and most effectively way of diagnosing rectal NETs. Colonoscopy is important in diagnosing the synchronous cancers and conducting a follow-up.