Single Rectal Neuroendocrine Tumor Associated with Multiple Endocrine Cell Micronests

Abstract

Although a few reports of neuroendocrine tumor (NET) in the stomach or appendix with surrounding micronests have been published, cases of rectal NET are rare. We herein report a unique case of a patient with single rectal NET treated endoscopically. A pathological examination revealed multiple endocrine cell micronests (ECMs) in the submucosal layer around the main NET lesion. Neither lymph node metastasis nor distant metastasis in computed tomography was observed six years after the treatment. Because case reports of multiple ECM are very rare, the significance of malignancy is unclear. It therefore appears to be necessary to accumulate similar cases.A 53-year-old man with no remarkable medical history of major illness and family history was referred to our hospital for endoscopic treatment of SMT in the rectum. Colonoscopy revealed a yellowish-white rectal SMT approximately 4 mm in diameter.The lesion did not show any irregularity of the vessels, irregularity of the surface pattern, or depression (Fig. 1). Endoscopic ultrasonography (EUS) (20 MHz, UM-DP20-25R;

A Case of Fifteen Simultaneous Rectal Neuroendocrine Tumors and Endocrine Cell Micronests Resected by Both Endoscopic Treatments and Surgery

“…In the current report, 2 cases with ≥4 lesions had ECM (Table 1 ), and there was no LNM. Similar to our 2 cases, some studies reported that cases with ECM did not have metastasis or recurrence [ 4 , 8 ]. A further large-scale study including genetic analysis should be performed to clarify the characteristics of ECM.…”

“…Most rectal NETs show a single lesion; however, there are some reports about multiple lesions [ 3 , 8 , 9 , 10 ]. It is not well understood why multiple lesions develop.…”

“…It has not been confirmed that ECM is a malignant lesion (pre-NET lesion) [ 4 , 8 ]. In the current report, 2 cases with ≥4 lesions had ECM (Table 1 ), and there was no LNM.…”

“…A Japanese largescale prospective study on rectal NET is now ongoing and will clarify this issue. Most rectal NETs show a single lesion; however, there are some reports about multiple lesions [3,[8][9][10]. It is not well understood why multiple lesions develop.…”