Metachronous liver metastases after long-term follow-up of endoscopic resection for rectal neuroendocrine neoplasms: a report of three cases

Abstract

Background: Rectal neuroendocrine neoplasms (NENs) are rare, but their incidence has increased in recent years. The metastasis rate is low in cases of a tumor diameter < 1 cm or depth of invasion lower than the submucosa; therefore, the European Neuroendocrine Tumor Society (ENETS) and the North American Neuroendocrine Tumor Society (NANETS) consensus guidelines recommend endoscopic resection. Since little has been reported on the long-term prognosis of endoscopic resection for rectal NEN, consensus is lacking regarding the follow-up period after endoscopic resection. Case presentation: Here, we report three cases of metachronous liver metastasis after long-term follow-up of endoscopic mucosal resection (EMR) for rectal NEN. The pathological findings indicated a depth lower than the submucosa and complete radical resection in all cases and lymphovascular invasion in only one case. All three cases showed metachronous multiple liver metastases after 9-13 years of follow-up for EMR, despite achieving complete resection and without muscular invasion. Conclusions: Metachronous liver metastases may occur after long interval following endoscopic resection; thus, long-term follow-up is necessary after endoscopic resection for rectal NEN.

Liver metastasis from rectal neuroendocrine neoplasm detected 15 years after primary resection

“…In the present case, low anterior resection with prophylactic lymphadenectomy was performed, because the tumor size had been expected to be 10 mm or more based on the preoperative endoscopic findings and the possibility of the existence of lymph node metastasis could not be ruled out. Recurrence occurred despite appropriate treatment according to ENETS recommendation in all previous cases except those reported by Hane et al [ 5 ]. Recurrence and survival in patients with rectal NEN depends on the tumor size, tumor depth, lymphovascular invasion, and mitotic rate [ 8 ].…”

“…We searched the English literature for reports of liver metastasis identified after a recurrence-free period of ≥ 5 years after rectal NEN resection [ 5 – 7 ] (Table 1 ). The European Neuroendocrine Tumor Society (ENETS) guidelines recommend endoscopic or local resection for tumors < 10 mm in size.…”

“…Thus, we can speculate lymphovascular invasion played an important role in provoking distant metastasis in this case. However, cases of recurrence without lymphovascular invasion have been reported [ 5 , 6 ]. Therefore, existing risk factors alone may not be sufficient to identify patients at risk of distant metastasis.…”