# Conversion Surgery after Chemotherapy in a Stage IV BRAF V600E‐Mutated Laterally Spreading Tumor With Neuroendocrine Component

## TL;DR

A patient with advanced colorectal cancer showed significant tumor regression after chemotherapy, allowing successful surgery and remaining cancer-free two years later.

## Contribution

This case demonstrates the potential effectiveness of conversion surgery in stage IV BRAF V600E-mutated colorectal cancer with a neuroendocrine component.

## Key findings

- Systemic chemotherapy led to significant regression of primary and metastatic lesions.
- Post-surgery pathology showed only tubular adenocarcinoma, with no remaining neuroendocrine carcinoma.
- The patient remained recurrence-free two years after surgery.

## Abstract

We report a rare case of a BRAF V600E‐mutated laterally spreading tumor, granular type (LST‐G), with a neuroendocrine carcinoma (NEC) component in a patient with stage IV colorectal cancer. The patient presented with multiple lymph nodes and liver metastases. Following systemic chemotherapy, significant regression of both the primary lesion and metastases was achieved, enabling successful conversion surgery. Postoperative pathological analysis post‐surgery revealed only well‐differentiated tubular adenocarcinoma, with complete disappearance of the NEC component. Molecular testing confirmed the persistence of the BRAF V600E mutation. The patient remains recurrence‐free two years after surgery. This case highlights the potential for conversion surgery in stage IV BRAF‐mutated colorectal cancer with NEC.