Renal cell carcinoma: a paradigm of lanthanic disease.

Renal cell carcinoma is characterized by varied and sometimes obscure manifestations, which include unusual metastatic sites and paraneoplastic and vascular syndromes. In this review, uncommon metastatic sites and their clinical significance are discussed, particularly the thyroid, nasal structures, vagina, and gastrointestinal sites. Paraneoplastic syndromes appear to be related predominantly to cytokines or immunologic mechanisms. Vascular syndromes are related to the tendency of the tumor to spread by direct venous extension and to complications related to the vascularity of the tumor or its metastases. The recognition of unusual manifestations of renal cell carcinoma is important because these syndromes may lead to the diagnosis. Moreover, paraneoplastic syndromes and vascular findings may not indicate unresectability or incurability.