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

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.