Duodenal metastasis from renal cell carcinoma (RCC) is rare. The current case report presents a very rare case of late duodenal metastasis from RCC with newly developed malignant lymphoma (diffuse large B-cell lymphoma: DLBCL) at the same time. A 64-year-old man with systemic lymph nodes swelling who had undergone left nephrectomy for RCC 25 years previously, was admitted to the present hospital. Inguinal lymph node biopsy was performed, leading to a diagnosis of DLBCL. fluorine-18-fluorodeoxy-glucose (18F-FDG)-positron emission tomography (PET)/computed tomography (CT) revealed multiple lymph nodes, spleen, and ileocecal lesions. CT revealed an obvious hypervascular tumor involving the duodenum/pancreatic head. The tumor was false-negative on 18F-FDG-PET/CT. On esophagogastroduodenoscopy, the tumor was detected in the descending portion of the duodenum and was observed to be consistent with the submucosal tumor with a central ulcer, resembling those of ulcer-forming DLBCL. A biopsy was then performed carefully, and a clear cell RCC-derived metastatic cancer was diagnosed. Ileocolonoscopy revealed mucosal thickening of the terminal ileum, and led to a diagnosis of DLBCL infiltration with biopsy. To the best of the author's knowledge, this is the first case report of the coexistence of metastatic cancer from RCC and malignant lymphoma in the small intestine simultaneously. It was necessary to make a careful differential diagnosis in the imaging studies.
Keywords: imaging study; late metastasis; malignant lymphoma; renal cell carcinoma; small intestine.