Clear cell renal cell carcinoma with syncytial giant cells: Not that rare

Syncytial giant cells (SGCs) are neoplastic giant cells of epithelial origin. The nuclear morphology of SGCs is uniform and similar to those of adjacent mononuclear tumor cells. Clear cell renal cell carcinoma (ccRCC) with SGCs is a rare microscopic morphology. In this study, the clinical and pathological data of 16 ccRCC cases with SGCs were retrospectively reviewed. The incidence of SGCs in pathological stages pT3 and above (12.1%, 8/66) was significantly higher than that in pT1 and pT2 (2.6%, 8/306) (P = 0.002). The incidence of SGCs in the WHO/ISUP nuclear grade 3 or 4 ccRCC (12.4%, 14/113) was significantly higher than that in grade 1 or 2 (0.8%, 2/259) (P < 0.001). Two forms of SGCs were observed, some exhibited nuclear pyknosis and degeneration. Of the 16 cases, eight cases were accompanied by necrosis and seven cases had lymphovascular invasion. Both SGCs and mononuclear tumor cells were positive for ccRCC markers (PAX8, CAIX, CD10 and Vimentin). None of the SGC nuclei were positive for Ki-67. Follow-up information was available on 14 patients, with a median follow-up time of 27.5 months. Ten patients were alive without disease, three were alive with metastatic disease, and one patient died 10 months after surgery. These findings indicated that SGCs are not rare, especially in ccRCC with high nuclear grade and pathological stage, and often co-exist with other adverse prognostic features. SGCs may be senescent tumor cells, the presence of SGCs should not be considered as Fuhrman and WHO/ISUP nuclear grading 4.