Hyaline globules in renal cell carcinoma and hepatocellular carcinoma: A clue or a diagnostic pitfall on fine-needle aspiration?

The cytologic similarity to hepatocellular carcinoma (HCC) of 2 cases of granular renal cell carcinoma (RCC) with hyaline globules (HGs) prompted us to evaluate the frequency of HGs in RCC and HCC and the association between cell type, differentiation, and malignant potential of these 2 neoplasms and the presence of HGs. We studied fine-needle aspirates from 23 cases of RCC (primary, 7; metastatic, 16) and 23 cases of primary HCC and noted anatomic site, tumor cell type, and presence, quality, and quantity of HGs. Fuhrman nuclear grade was assigned to RCC and overall differentiation to HCC cases. RCC cell type was granular (7), mixed (4), and clear (12). HCC cases were granular (22) and clear (1). Morphologically similar, predominantly intracytoplasmic HGs were identified in 4 RCCs and 10 HCCs. All 4 RCCs with HGs were at metastatic sites, granular cell type, and high Fuhrman grade. HGs showed no association with differentiation of HCC. While HGs are seen more commonly in HCC than in RCC, their presence in an adenocarcinoma should bring renal origin into consideration. The presence of HGs in metastatic granular RCC, particularly in the liver, can lead to misinterpretation as primary HCC.