Renal cell carcinoma with syncytial giant cell component

We report a case of clear cell renal cell carcinoma in which a prominent multinucleated giant cell component was intermingled with clear, granular, and spindle cells. Histological, ultrastructural, cytometric, and cytogenetic features of giant cells were similar to those of mononucleated cells in the tumor, and therefore they were not from stromal or osteoclast derivation. These giant cells had homogeneous, finely granular, abundant cytoplasm, often with scalloped cell borders, and contained from 5 to more than 50 nuclei, all of them very similar in size and shape, with prominent central nucleoli. Occasionally, surrounding inflammatory cells were also engulfed in the cytoplasm. This syncytial appearance was more similar to that of some giant cell carcinomas from the lung than to the pleomorphic giant cells often encountered in high grade renal cell tumors. Although the patient is alive and free of disease 6 years after diagnosis, a longer follow-up will be required to assess the potential prognostic influence of this peculiar histological appearance.