講演情報
[INTS3-3]Clinicopathological Factors Associated with Lymph Node Metastasis and Surgical Implications in Rectal Neuroendocrine Tumors
*Takashi Okumura1, Kenji Baba1, Shizuka Yoshidome1, Taiki Nakashima1, Naohiro Koyoshi2, Hidehito Maeda2, Fumisato Sasaki2, Ohtsuka Takao1 (1. Department of Digestive Surgery, Kagoshima University, Japan 2. Department of Digestive and Lifestyle Diseases, Kagoshima University, Japan)
Background:
Rectal neuroendocrine tumors (NETs) generally have a favorable prognosis; however, lymph node metastasis can occur even in small tumors, making treatment decisions difficult. The clinical practice guidelines for gastroenteropancreatic neuroendocrine neoplasms (NENs) were revised from the 2019 to the 2023 edition, emphasizing risk stratification based on tumor size and depth of invasion to guide the selection between endoscopic treatment and surgical resection. However, the indications for additional surgical resection after endoscopic treatment remain controversial.
Methods:
We retrospectively analyzed 15 patients who underwent rectal resection with lymph node dissection for rectal NETs at our institution between 2014 and 2026. The association between clinicopathological factors and lymph node metastasis was evaluated.
Results:
The cohort included 15 patients (9 males, 6 females) with a median age of 58 years (range, 37–78). Tumor location was Ra in 1 case and Rb in 14 cases. Three patients underwent additional surgery after endoscopic resection. Histologically, there were 9 G1, 5 G2, and 1 NEC cases. Lymph node metastasis was observed in 9 patients.
No lymph node metastasis was observed in tumors <10 mm, whereas tumors ≥10 mm showed a significantly higher rate of metastasis (p = 0.044). All tumors with invasion beyond the muscularis propria (≥T2) had lymph node metastasis and were significantly associated with metastasis compared with T1 tumors. In contrast, tumor grade, lymphatic invasion, and venous invasion were not significantly associated with lymph node metastasis.
Conclusions:
Tumor size and depth of invasion were significantly associated with lymph node metastasis in rectal NETs. Lymphovascular invasion alone may be insufficient to determine the indication for additional surgery.
Rectal neuroendocrine tumors (NETs) generally have a favorable prognosis; however, lymph node metastasis can occur even in small tumors, making treatment decisions difficult. The clinical practice guidelines for gastroenteropancreatic neuroendocrine neoplasms (NENs) were revised from the 2019 to the 2023 edition, emphasizing risk stratification based on tumor size and depth of invasion to guide the selection between endoscopic treatment and surgical resection. However, the indications for additional surgical resection after endoscopic treatment remain controversial.
Methods:
We retrospectively analyzed 15 patients who underwent rectal resection with lymph node dissection for rectal NETs at our institution between 2014 and 2026. The association between clinicopathological factors and lymph node metastasis was evaluated.
Results:
The cohort included 15 patients (9 males, 6 females) with a median age of 58 years (range, 37–78). Tumor location was Ra in 1 case and Rb in 14 cases. Three patients underwent additional surgery after endoscopic resection. Histologically, there were 9 G1, 5 G2, and 1 NEC cases. Lymph node metastasis was observed in 9 patients.
No lymph node metastasis was observed in tumors <10 mm, whereas tumors ≥10 mm showed a significantly higher rate of metastasis (p = 0.044). All tumors with invasion beyond the muscularis propria (≥T2) had lymph node metastasis and were significantly associated with metastasis compared with T1 tumors. In contrast, tumor grade, lymphatic invasion, and venous invasion were not significantly associated with lymph node metastasis.
Conclusions:
Tumor size and depth of invasion were significantly associated with lymph node metastasis in rectal NETs. Lymphovascular invasion alone may be insufficient to determine the indication for additional surgery.