Abstract
BackgroundTo compare clinicopathologic feature of rectal neuroendocrine tumor (NET) grade G1 with G2 NET.MethodsSix hundred-one cases of rectal G1 and G2 NETs diagnosed in our center were analyzed.ResultsOf 601 cases of rectal NET, 515 cases were with grade G1 and 86 cases were with grade G2. Median tumor size was 0.7 cm. Compared with G1 NET, G2 tumors were with significantly larger tumor size (0.8 vs 2.2 cm, p < 0.001), less percentages of patients with tumors confined to submucosa (92.6 vs 42.8%, p < 0.001), more frequent presence of microvascular invasion (MVI) (3.6 vs 16.9%, p < 0.001) or peri-neural invasion (PNI) (2.0 vs 24.1%, p < 0.001). Incidence of lymph node and distant metastasis was 5.2 and 2.1% in G1 NET compared with 44.2 and 31.4% in G2 tumor, respectively (p < 0.001). For tumors sized 1–2 cm and confined to submucosa, incidence of lymph node metastasis was 6.1% for G1 NET compared with 21.1% for G2 NET. Status of MVI/PNI was predictive of lymph node metastasis for G2 tumor rather than G1 NET in this subgroup.ConclusionsRectal G2 NET was much more invasive with significantly elevated prevalence of lymph node metastasis compared with G1 tumor.
Highlights
Neuroendocrine tumor (NET) of the rectum includes three subgroups of tumors with great heterogeneity
Our results demonstrated that, compared with G1 neuroendocrine tumor (NET), G2 tumors were with significantly larger tumor size, deeper invading depth, more frequent presence of microvascular invasion or peri-neural invasion, which were associated with elevated incidence of lymph node metastasis and distant metastasis
From 1981 to 2018, 656 cases of rectal neuroendocrine tumors (NET) were diagnosed and treated in Shanghai Cancer Center Fudan University (FUSCC). 55 cases were excluded from analysis, of which 40 cases were with accompanied malignancy of other origin, 5 cases were with indeterminate tumor size, 6 cases were with unknown tumor invading depth and 4 cases were with uncertain pathology (Figure 1)
Summary
Neuroendocrine tumor (NET) of the rectum includes three subgroups of tumors with great heterogeneity. Data from National Cancer Database of the America included 16,531 cases of rectal NET from 2004 to 2015, of which tumor grade was unknown in 59.9% of patients [4]. Since G1 tumor accounts for approximately 80–90% of rectal NET. This would underestimate the metastatic risk of this disease. Few studies have focused on detailed information about clinicopathologic feature, treatment modality and prognosis of rectal NETs based on different grades (G1/G2/G3). Direct comparison of rectal NET G1 with G2 tumor is necessary regarding more precise therapy. To compare clinicopathologic feature of rectal neuroendocrine tumor (NET) grade G1 with G2 NET
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