Renal Cell Carcinoma Metastatic to the Thyroid Gland: A Comparative Molecular Study Between the Primary and the Metastatic Tumor.

A case of renal cell carcinoma metastatic to the thyroid gland is presented. The thyroid tumor showed typical features: clear cells arranged in nests with a prominent sinusoidal vascular pattern. The histologic appearance was identical to the renal tumor removed 6 yr before. A comparative molecular study between the primary and the metastatic tumor showed a common profile with a loss of heterozygosity at identical loci on chromosome 3, which provided further support to the metastatic nature of the thyroid tumor. However, the frequent existence of allele losses on chromosome 3p in both renal cell carcinomas and primary thyroid follicular carcinomas rest some force from such a molecular approach to the differential diagnosis of thyroid tumors that contain a predominant population of clear cells.