Thyroid metastases from renal clear cell carcinoma: a cyto-histological study of two cases.

AIMS: We report about two cases of thyroid metastases, with neoplastic thrombosis of the jugular vein, originating from a renal clear cell carcinoma and arising respectively 5 and 18 years after the original nephrectomies. MAIN RESULTS AND CONCLUSIONS: The first patient had also a synchronous transitional cell carcinoma of the bladder and a poorly differentiated prostatic adenocarcinoma, further complicating the location of the primary sources of the metastases. The metastases of the first case were firstly diagnosed by mean of fine needle aspiration biopsy, and subsequently histologically confirmed. Histochemical (diffuse PAS-positive cytoplasms) and immunohistochemical stains (wide spectrum cytokeratins low molecular cytokeratins+, Ck8+, CD10+, Vimentin+, Ck20-, Ck7-, Ck19-, PSA-, thyreoglobulin-, TTF-) performed both on cytologic and histological material helped to define the metastases as oriinating from the renal clear cell carcinoma. For the first patient, the other two possible primary sources were ruled out and a possible primary thyroid tumor with clear cell change was also excluded for both patients.