Clinical and pathological characteristics and prognosis of 132 cases of rectal neuroendocrine tumors

Abstract

Background: Neuroendocrine tumors (NETs) frequently occur in the gastrointestinal tract, lung, and pancreas, and the rectum and appendix are the sites with the highest incidence. Epidemiology statistics show that an estimated 8000 people every year in the United States are diagnosed with NETs occurring in the gastrointestinal tract, including the stomach, intestine, appendix, colon, and rectum. The pathological changes and clinical symptoms of NETs are not specific, and therefore they are frequently misdiagnosed.

Aim: To investigate the clinical symptoms, pathological characteristics, treatment, and prognosis of rectal neuroendocrine tumors (RNETs) by analyzing the clinical and pathological data of 132 RNET cases at our hospital.

Methods: All RNETs were graded according to Ki-67 positivity and mitotic events. The tumors were staged as clinical stages I, II, III, and IV according to infiltrative depth and tumor size. COX proportional hazard model was used to assess the main risk factors for survival.

Results: These 132 RNETs included 83 cases of G1, 21 cases of G2, and 28 cases of G3 (neuroendocrine carcinoma) disease. Immunohistochemical staining showed that 89.4% of RNETs were positive for synaptophysin and 39.4% positive for chromogranin A. There were 19, 85, 23, and 5 cases of clinical stages I, II, III, and IV, respectively. The median patient age was 52.96 years. The diameter of tumor, depth of invasion, and pathological grade were the main reference factors for the treatment of RNETs. The survival rates at 6, 12, 36, and 60 mo after operation were 98.5%, 94.6%, 90.2%, and 85.6%, respectively. Gender, tumor size, tumor grade, lymph node or distant organ metastasis, and radical resection were the main factors associated with prognosis of RNETs. Multivariate analysis showed that tumor size and grade were independent prognostic factors.

Conclusion: The clinical symptoms of RNETs are not specific, and they are easy to misdiagnose. Surgery is the main treatment method. The grade and stage of RNETs are the main indices to evaluate prognosis.

Keywords: Neuroendocrine carcinoma; Neuroendocrine tumors; Prognosis; Tumor grade; Tumor size; Univariate analysis.

Figure 1

Representative rectal neuroendocrine tumor morphology and histochemistry. A: a. Gross morphology of a G1 rectal neuroendocrine tumor (RNET) (black arrow heads the tumor); b. Gross morphology of a G2 RNET (black arrow heads the tumor); c. Gross morphology of a neuroendocrine carcinoma (black arrow heads the tumor). The diameter of the rectal tumor was approximately 2.0 cm, and it was 11 cm away from the anus. Pathological examination confirmed that it was a neuroendocrine carcinoma. B: a. Hematoxylin and eosin (HE) staining of a G1 RNET (× 100); b. HE staining of a G2 RNET (× 100); c. HE staining of a rectal neuroendocrine carcinoma (× 100); d. Ki-67 staining in a G1 RNET (black arrow heads the positive staining; × 100); e. Ki-67 staining in a G2 RNET (black arrow heads the positive staining; × 100); f. Ki-67 staining in an rectal neuroendocrine carcinoma (black arrow heads the positive staining; × 100).

Figure 2

Immunohistochemical features. A: Positive synaptophysin immunohistochemical staining in a G2 rectal neuroendocrine tumor (RNET) (black arrow heads the positive staining; × 100). B: Negative synaptophysin immunohistochemical staining in an RNEC (× 100); C: Positive chromogranin A immunohistochemical staining in a G1 RNET (black arrow heads the positive staining; × 100); D: Negative chromogranin A immunohistochemical staining in an RNEC (× 100); E: Lymph node metastasis of a G2 RNET (black arrow shows the tumor tissue; hematoxylin and eosin staining, × 100); F: Black arrow shows a thrombus in the lymph vessel (hematoxylin and eosin staining, × 100).