# Comparison of clinicopathological characteristics and survival outcomes between solitary and multiple rectal neuroendocrine tumors: a propensity score-matched study

## TL;DR

This study compares solitary and multiple rectal neuroendocrine tumors, finding that multiple tumors are more homogeneous but have higher risks of metastasis and recurrence.

## Contribution

The study reveals distinct clinicopathological differences and higher metastatic potential in multiple rectal neuroendocrine tumors compared to solitary ones.

## Key findings

- Multiple RNETs show homogeneous WHO grading and SSTR2 expression.
- Solitary RNETs have higher SSTR2 positivity but lower chromogranin A positivity.
- Multiple RNETs are associated with higher metastasis/recurrence risks.

## Abstract

Multiple rectal neuroendocrine tumors (RNETs) are rare rectal malignancies, and there is no consensus on their characteristics and treatments. This study aimed to explore the heterogeneity of key morphological parameters in multiple RNETs and to compare the clinicopathological characteristics between multiple and solitary RNETs.

A total of 15 patients with multiple RNETs and 89 patients with solitary RNETs treated between 2013 and 2024 were retrospectively analyzed using propensity match analysis to determine their clinicopathological characteristics. WHO grade, the expression of basal diagnostic markers (synaptophysin/chromogranin A/CD56), and somatostatin receptor 2 (SSTR2) were analyzed. Disease-free survival rates were calculated using the Kaplan–Meier method.

Multifocal RNETs were characterized by homogeneous WHO grading (93.3%) and concordant SSTR2 expression. The solitary RNETs group had a significantly higher SSTR2 positivity rate (p < 0.05) but significantly lower chromogranin A positivity rate than the multiple RNETs group (p < 0.05).

Multiple RNETs demonstrate remarkable homogeneity in core diagnostic parameters. However, compared to solitary RNETs, multifocal presentations exhibit a significantly higher propensity for metastasis/recurrence, warranting intensified therapeutic protocols and enhanced clinicopathological surveillance paradigms.