Metastatic Sarcomatoid Carcinoma to Liver and Bone Marrow in Renal Transplant Recipient: Due to Exacerbation of Quiescent Renal Cancer? A Case Report

Sarcomatoid carcinoma is a rare tumor with rapid growth and a poor prognosis. A 60-year-old man underwent kidney transplantation. Three months after transplantation, multiple tumors were found in the liver and bone, and the patient died several days later. Pathological examination of liver and bone marrow biopsies revealed metastatic sarcomatoid carcinoma. Pretransplantation, the patient's workup was positive only for mild thrombocytopenia and a complicated cyst with peripheral rim calcification (Bosniak IIF) in the right kidney. Retrospectively, we found the abdominal computed tomography film, which had been examined at another hospital 6 years previously. The calcified complicated cyst was a 3-cm enhancing solid mass in the right kidney, suggesting renal cell cancer. It is possible that the cancer developed from the calcified complicated cyst. In this case, immunosuppressants may have altered malignant cell proliferation, invasion, and the form of metastasis.