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Rare Benign Mass Mimics Recurrent Renal Cell Carcinoma: Case Report

By: Celeste L. Dixon
Posted: Thursday, May 9, 2019

What turned out to be a multinucleate giant cell (MGC) reaction—not recurrent renal cell carcinoma—has been described by a team of two urologists and a pathologist in Case Reports in Urology. David D. Thiel, MD, of the Mayo Clinic in Jacksonville, Florida, explained that the retroperitoneal perinephric mass was surgically resected after it was observed near the original renal cell carcinoma; then it was pathologically confirmed as tumefactive fat necrosis with an MGC reaction.

Dr. Thiel and his team shared the lesson they learned: consider “every possibility when presented with a patient [who] develops new perinephric abnormalities following ablation.” Doing so could help to avoid “unnecessary invasive treatments for suspicious but nonmalignant lesions.”

The case report featured a 60-year-old man. His original mass, definitively clear cell renal cell carcinoma, had been removed via cryoablation 2 years earlier, wrote Dr. Thiel and colleagues. He had remained cancer-free throughout follow-up, until this mass was discovered. Presurgical “biopsy was foregone due to the new rapid development, consistency, and location of the lesion,” and it was expediently removed with an open subcostal partial nephrectomy with complete perinephric fat removal.

Subsequent immunohistochemistry studies of the tissue demonstrated not cancer, but “an inflammatory reaction characterized by abundant histiocytes and MGCs that were positive for CD68,” the team described. Rarely, an MGC reaction can occur after tissue ablation, and this patient’s “unique combination of both [an] MGC reaction and tumefactive fat necrosis may have contributed to the delayed presentation on imaging…allowing the reaction to mimic renal cell carcinoma recurrence in the cryoablative tract.”

Disclosure: The study authors reported no conflicts of interest.

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