Perirenal metastasis of anaplastic transformation of lung adenocarcinoma: a case report and literature review

The kidneys are a not uncommon site for metastatic spread of lung cancer; however, spread to the perirenal space is exceedingly rare. A 65-year-old man was admitted with right back pain and fever. Abdominal computed tomography (CT) revealed diffuse stranding around the right renal pelvis that seemed like peripelvic extravasation. Treatment with a ureteral stent and antibiotics was performed, but his general condition worsened. Thirteen days after admission, abdominal CT was performed and showed that the stranding lesion had changed to a soft tissue mass; there was swelling of the reniportal lymph nodes, hepatic portal lymph nodes and bilateral adrenal glands. We suspected metastases to the right perirenal space, lymph nodes and bilateral adrenal glands from a primary cancer of unknown origin. Chest CT revealed two lung nodules, and a percutaneous needle biopsy was performed. The histopathological diagnosis was moderately differentiated adenocarcinoma. The patient's general condition rapidly worsened, and he died 26 days after admission. An autopsy demonstrated perirenal metastasis of anaplastic transformation of lung adenocarcinoma and secondary progression to the retroperitoneal and intraabdominal space and lymph nodes. We review the published series in the literature describing perirenal metastasis of lung cancer.