Tumefactive Fat Necrosis with Multinucleate Giant Cell Reaction Mimicking Recurrent Renal Cell Carcinoma following Percutaneous Renal Cryoablation

Figure 3

Pathology of lesion following partial nephrectomy. (a) Pathology of lesion showing area with prominent hemosiderin laden macrophages and multinucleate giant cells (H/E, 20X). Lower inset demonstrating foci of giant cells associated with cholesterol clefts (arrow) (H/E, 20X). Upper inset shows necrotic fat (arrow) with surrounding inflammatory reaction (H/E, 4X). (b) CD68 (KP1) immunohistochemistry (10X). CD68 is highly expressed by monocytes, macrophages, and histiocytes and is positive in numerous histiocytes and macrophages in adipose tissue. (c) Immunohistochemistry demonstrating a negative study for cytokeratin AE1/AE3 confirming no recurrence of renal cell carcinoma (10X). (d) Immunohistochemistry demonstrating a negative study for PAX-8 confirming no recurrence of renal cell carcinoma (10X).

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