# Resection of a Pulmonary Hamartoma That Transformed into Stage IVB Lung Cancer over a 4-Year Period: A Case Report

## TL;DR

A benign lung tumor initially diagnosed as a hamartoma transformed into stage IVB lung cancer over four years and was successfully treated with surgery and radiotherapy.

## Contribution

This case highlights the rare malignant transformation of a pulmonary hamartoma and the effectiveness of aggressive treatment in an oligometastatic setting.

## Key findings

- A 20-mm pulmonary hamartoma grew to 66 mm over four years and transformed into stage IVB large-cell neuroendocrine carcinoma.
- The patient's tumors responded to chemotherapy and were deemed oligometastatic, leading to successful surgical resection and radiotherapy.
- The patient remained recurrence-free for 8 months post-treatment, suggesting the benefits of aggressive intervention in such cases.

## Abstract

Pulmonary hamartoma (PH) is the most frequent benign tumor of the lung; however, the induction of malignant tumors and malignant transformation has been reported.

The patient was a woman in her 80s.Two transbronchial biopsies were performed for a 20-mm nodule in the S8 segment of the right lung, which showed a growing trend, and both were diagnosed as PH. Subsequently, she discontinued her outpatient visits but returned 4 years later with a complaint of blood in her sputum, and the right lung tumor had increased to 66 mm. In addition, a 35-mm tumor was found in the left lung S1+2 segment and a 35-mm tumor in the liver, and a diagnosis of cT3N0M1c stage IVB combined with large-cell neuroendocrine carcinoma was made. After chemotherapy, all tumors had shrunk, and no new lesions were detected, so the disease was judged to be oligometastatic, with localized metastases. Therefore, the patient underwent surgical resection of the primary tumor and radiotherapy for the metastases. As a result, the patient was alive and recurrence-free 8 months postoperatively.

The possibility of accidental malignant transformation of components or surrounding tissues cannot be ruled out in PH, and careful follow-up and aggressive surgical resection should be considered, especially for lesions that increase in size over a short period.