Appendiceal neuroendocrine tumors: a case series and literature review

Abstract

Appendiceal neuroendocrine tumors (ANETs) are rare gastrointestinal malignancies that are often diagnosed incidentally during or after surgery for suspected appendicitis, presenting significant diagnostic challenges. Existing studies primarily focus on the epidemiology and management of ANETs but lack comprehensive analyses of diagnostic limitations and treatment outcomes. This study presents five cases of ANETs, emphasizing the ongoing challenges in preoperative diagnosis. Consistent with the medical literature, tumors smaller than 1 cm were effectively managed with appendectomy, whereas a larger tumor with high-risk features necessitated right hemicolectomy. Preoperative imaging consistently failed to identify the tumors, underscoring its limitations in detecting neoplastic causes of appendicitis. These findings highlight the need for larger-scale studies, the development of advanced imaging techniques-particularly with the integration of artificial intelligence-and standardized follow-up protocols for high-risk cases.

Keywords: abdominal pain; appendectomy; appendiceal neuroendocrine tumors; appendix; hemicolectomy; neuroendocrine tumor.

Figure 1

Light microscopy photographs of the appendix show (A) a well-differentiated grade 1 neuroendocrine tumor invading through the muscularis propria into the subserosa, located in the distal half of the appendix. The tumor cells are diffusely positive for (B) synaptophysin and (C) panCK. The Ki-67 labeling index is < 1% (hematoxylin and eosin stain; 2×).

Figure 2

Light microscopy photographs of the appendix show (A) a well-differentiated grade 1 neuroendocrine tumor invading from the submucosa into the muscularis propria, located in the distal half of the appendix (tip). The tumor cells are diffusely positive for (B) synaptophysin (hematoxylin and eosin stain; 2×).

Figure 3

Light microscopy photographs of the appendix show (A, B) a well-differentiated grade 1 neuroendocrine tumor invading from the muscularis propria into the subserosa, located in the distal half of the appendix (tip). The tumor cells are positive for (C) synaptophysin but negative for (D) chromogranin A and (E) CD56. The Ki-67 labeling index is less than 3% (hematoxylin and eosin stain; 2×).

Figure 4

Light microscopy photographs of the appendix show (A) a well-differentiated grade 1 neuroendocrine tumor invading from the muscularis propria into the mesoappendiceal fat, located in the distal half of the appendix. The tumor cells are positive for (B) synaptophysin and (C) CD56 (hematoxylin and eosin stain; 2×).

Figure 5

Light microscopy photographs of the appendix show (A) a well-differentiated grade 1 neuroendocrine tumor invading from the submucosa into the muscularis propria, located in the distal half of the appendix. The tumor cells are strongly positive for (B) synaptophysin and (C) chromogranin. The Ki-67 labeling index is less than 2% (hematoxylin and eosin stain; 2×).