LIPID-LADEN FOAMY MACROPHAGES IN RENAL-CELL CARCINOMA - POTENTIAL FROZEN-SECTION DIAGNOSTIC PITFALL

Lipid-laden foamy macrophages are characteristic of xanthogranulomatou s pyelonephritis (XGP). We have encountered a case of renal cell carci noma (RCC), with extensive necrosis, in which confluent sheets of foam y macrophages were a dominant feature. We describe the case and discus s the potential frozen section diagnostic problem in attempting to dis tinguish between confluent sheets of xanthoma cells as a ''reactive'' change in RCC and xanthoma cells as a fundamental component of XGP. We propose that awareness of that problem should prompt the pathologist to request additional samples.