# BRAF V600E-mutated lung adenocarcinoma with thyroid metastasis as the initial manifestation: a case report

## TL;DR

A rare case of lung cancer with thyroid metastasis was successfully treated with targeted therapy after a BRAF mutation was identified.

## Contribution

This case report highlights the rare occurrence of thyroid metastasis from lung adenocarcinoma and successful treatment with BRAF-targeted therapy.

## Key findings

- Thyroid metastasis from lung adenocarcinoma was confirmed via histopathological and immunohistochemical analysis.
- BRAF V600E mutation was detected and targeted with dual therapy, leading to a positive clinical outcome.
- The patient remained alive six months post-treatment, indicating the effectiveness of the targeted therapy.

## Abstract

Thyroid metastasis of lung adenocarcinoma is exceedingly uncommon. Here we present a case of a 72-year-old Chinese male with hoarseness, dysphagia, pain, and palpable thyroid nodules. Ultrasonography-guided thyroid fine-needle aspiration cytology (FNAC) suggested a high-grade follicular-derived thyroid carcinoma (HGFCTC). Molecular analysis identified a BRAF V600E mutation. Comprehensive histopathological and immunohistochemical examinations, however, revealed that the thyroid cancer originated from the left lung. The patient received a 6-month post-operative dual-target therapy with dalafenib and trametinib. As of the last follow-up, the patient was still alive, demonstrating the effectiveness of targeted therapy.