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Clinicopathological characteristics and frequency of multiple rectal neuroendocrine tumors: a single-center
Yusuke Nishikawa1,2, Akiko Chino3, Daisuke Ide1
1Department of Gastroenterology, Cancer Institute Hospital, Japanese Foundation for Cancer Research, Tokyo, Japan.
Background:
Rectal multiple neuroendocrine tumors (M-NETs) are rare, with only few epidemiologic reports on the topic. Therefore, their clinicopathological features are not completely known, and the appropriate treatment strategy has not been established.
Purpose:
This study aimed to compare the clinicopathological malignant potential (lymphatic or venous invasion-positive and lymph node metastasis rates) of M-NETs with that of solitary NETs (S-NETs).
Methods:
We retrospectively investigated 369 patients with NETs of the rectum. Patients who underwent colonoscopy at the Cancer Institute Hospital between January 1979 and 2016 and diagnosed with S-NETs were included, and S-NETs were found in 348 patients. Patients with M-NETs were classified into two groups as follows: patients with < 8 tumors (several (S) group, n = 21) and those with ≥ 8 tumors (numerous (N) group, n = 3).
Results:
The overall frequency of M-NETs was 5.7% and that of the N group was 0.8%. The mean tumor diameter in the N group was 6.0 mm (range, 4-8 mm). The lymphatic invasion rates of the S-NETs, and S and N groups of the M-NETs were 8.9%, 5.6%, and 66.7%, respectively. Moreover, the lymph node metastasis rates were 9.2%, 11.1%, and 33.3, respectively.
Conclusions:
While M-NETs in the S and N groups had different characteristics, they were rarer in the N group. The N group may have higher rates of lymphatic invasion and lymph node metastasis regardless of tumor size.
