Renal transplants with perinephric myxoid pseudotumor of fat mimicking malignancy

A 55-year-old man with end stage renal disease (ESRD), two failed renal transplants and on hemodialysis, had a heterogeneous mass medial to the second failed transplant (Fig. 1). Biopsy and surgery diagnosed perinephric myxoid pseudotumor (PNMP) of fat. The patient had the transplant resected and is currently on waiting list for new transplantation. The renal specimen was infiltrated by a myxoid process, spindled stromal cells and an inflammatory background without evidence of malignancy. Epstein–Barr-encoded RNA (EBER) in situ hybridization and fluorescent in situ hybridization (FISH) for murine double minute-2 (MDM2) amplification were negative for EBV-related posttransplant process and liposarcoma/atypical lipomatous tumor, respectively. Immunohistochemistry (IHC) for IgG/IgG4 was also negative. A 59-year-old man with ESRD and on hemodialysis after a failed living donor renal transplant, consulted our institution for a heterogeneous mass encasing the transplant (Fig. 2). Biopsy showed PNMP of fat. FISH for MDM2...