Retroperitoneal Metastasis, with Marked Fibrosis, of Lung Adenocarcinoma after Afatinib Treatment: An Autopsy Case Report.

A 73-year-old woman was admitted to our hospital for treatment of vomiting. Four months previously, she had been diagnosed with lung adenocarcinoma (cT3N3M1a stage IVA) and started receiving afatinib as first-line treatment. On admission, the primary tumor had shrunk, but abdominal computed tomography revealed a new retroperitoneal lesion causing duodenal obstruction and hydronephrosis. She underwent gastrojejunostomy, and a biopsy of the peritoneum revealed adenocarcinoma. She was treated with second-line chemotherapy but developed cerebral infarction and died 104 days after admission. An autopsy revealed marked fibrosis with scattered tumor cells in the retroperitoneum. The underlying mechanism of the metastasis is discussed.