Case report: perinephric myxoid pseudotumour of fat in a patient with chronic kidney disease detected during renal transplant workup

Perinephric myxoid pseudotumour of fat (PMPTF) is a recently defined rare entity with exact pathophysiology yet to be fully elucidated. 1-3 Thought to be non-neoplastic, the current literature demonstrates an association with chronic renal conditions, both non-neoplastic and neoplastic, and even vague regional insults. 3 Here, we describe a case of PMPTF in a male patient in the sixth decade of life, presenting with a perinephric mass found incidentally on CT imaging for renal transplant workup. Macroscopically, it was pedunculated and gelatinous. Microscopy demonstrated a myxoid lesion with interspersed adipocytes and no atypia, arising from perinephric fat. Well-differentiated liposarcoma was an important differential consideration, amongst others, and excluded following negative MDM2 fluorescence in-situ hybridisation. This case illustrates the diagnosis of PMPTF in the appropriate clinical context and the use of ancillary techniques to avoid misdiagnosis leading to over-treatment.