A large calcified retroperitoneal mass in a patient with chronic renal failure: liposarcoma with ossification.

Here we describe a 65-year-old Japanese man with chronic renal failure (CRF) and a large, dense, calcified abdominal mass. The patient had a history of proteinuria, which was diagnosed as focal glomerulosclerosis. This diagnosis was confirmed by renal biopsy in 2002, with worsening renal function by July 2005 when a large area of calcification was detected on abdominal radiography, which further increased in size on follow-up radiography in December 2006. The calcified mass was surgically resected and histopathologically diagnosed as myxoid-type liposarcoma composed of dedifferentiated, myxoid, and well-differentiated components with areas of osseous metaplasia. Soft tissue calcifications and ossifications are often benign, but malignant tumors should be considered when the calcified mass is retroperitoneal, occurs in a patient with no history of chronic infection, and is not located near a large joint or associated with administration of calcium carbonate or a vitamin D derivative.