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Published on: March 30, 2015
Perinephric myxoid pseudotumor of fat: a multimodality imaging case series
Justin Lee1, Kevin G King2, Shefali Chopra3
1Department of Radiology, Keck School of Medicine of USC, Los Angeles, CA, USA.
Abstract:
Perinephric myxoid pseudotumor of fat (PMPF) is an unusual clinical entity with few prior imaging case reports. We report a multimodality imaging case series of PMPF, consisting of four cases seen in our department with both imaging studies and histopathologic confirmation. Three of the four patients had a history of advanced non-neoplastic renal disease. The perirenal masses in these cases varied in size and appearance. Some lesions resembled cysts or contained macroscopic fat. Enhancement was equivocal on CT, but prominent in one case on MRI and in another on contrast-enhanced ultrasound. Although not known to be malignant, PMPF may be confused for a cyst, liposarcoma, or hypovascular solid neoplasm on imaging. The dominant mass was resected in two cases because of concern for malignancy, while percutaneous CT-guided biopsy was performed in the other two. Mouse double minute 2 (MDM2) gene amplification by fluorescence in situ hybridization (FISH) was negative in all four cases, excluding well-differentiated liposarcoma. Radiologists should be familiar with PMPF to provide appropriate guidance on clinical management.
Insights
Perinephric myxoid pseudotumor of fat (PMPF) is a rare kidney mass that can mimic other lesions. Imaging and MDM2 FISH testing help differentiate PMPF from malignancy.
Area of Science:
- Radiology
- Pathology
- Oncology
Background:
- Perinephric myxoid pseudotumor of fat (PMPF) is an uncommon entity.
- Few imaging case reports exist for PMPF.
- Three of four patients had advanced non-neoplastic renal disease.
Purpose of the Study:
- To describe the multimodality imaging features of PMPF.
- To highlight diagnostic challenges and aid radiologists in clinical management.
Main Methods:
- Retrospective review of four PMPF cases with imaging and histopathologic confirmation.
- Multimodality imaging included CT, MRI, and contrast-enhanced ultrasound.
- Fluorescence in situ hybridization (FISH) for MDM2 gene amplification was performed.
Main Results:
- Perinephric masses varied in size and appearance, some resembling cysts or containing fat.
- Enhancement patterns were equivocal on CT, but visible on MRI and ultrasound in some cases.
- MDM2 FISH was negative in all cases, excluding well-differentiated liposarcoma.
Conclusions:
- PMPF can be mistaken for cysts, liposarcoma, or hypovascular neoplasms.
- Familiarity with PMPF imaging characteristics is crucial for accurate diagnosis and management.
- Negative MDM2 FISH aids in excluding liposarcoma.
