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

Yuma Hane,Yuma Ebihara,Yo Kurashima,Soichi Murakami,Toru Nakamura,Takehiro Noji,Takahiro Tsuchikawa,Satoshi Hirano,Keisuke Okamura,Kimitaka Tanaka,Toshiaki Shichinohe,Yoshitsugu Nakanishi,Satoshi Takeuchi,Toshimichi Asano

doi:10.1186/s40792-020-0792-5

Yuma Hane, Yuma Ebihara + Show 12 more

Open Access

https://doi.org/10.1186/s40792-020-0792-5

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Abstract

BackgroundRectal 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 presentationHere, 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.ConclusionsMetachronous liver metastases may occur after long interval following endoscopic resection; thus, long-term follow-up is necessary after endoscopic resection for rectal NEN.

Highlights

Rectal neuroendocrine neoplasms (NENs) are rare, but their incidence has increased in recent years
Metachronous liver metastases may occur after long interval following endoscopic resection; long-term follow-up is necessary after endoscopic resection for rectal NEN
Regarding indications of endoscopic tumor resection for rectal NEN, North American Neuroendocrine Tumor Society (NANETS) and Japanese Neuroendocrine Tumor Society (JNETS) guidelines recommend endoscopic resection in cases of a tumor < 10 mm without muscular invasion [7], while European Neuroendocrine Tumor Society (ENETS) guidelines recommend it in cases of a tumor < 10 mm, G1 or G2, and no muscular invasion [6] because the metastasis rate at diagnosis is reportedly low in 3–9.7% of tumors measuring < 10 mm [4, 5]

Summary

Conclusions

Metachronous metastases may occur from endoscopic resection to a long period thereafter; long-term followup is necessary after endoscopic resection for rectal NEN. No consensus has been reached on follow-up period or modality after endoscopic resection for rectal NEN. This report may assist with the determination of follow-up strategy after endoscopic resection for rectal NEN. Features of recurrent cases – Tumor size 20 mm Positive resection margin, muscular invasion Positive resection margin

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