Metastasis from papillary renal cell carcinoma masquerading as primary ovarian clear cell tumor.

A 73-year-old female presented with a left ovarian tumor mass. Microscopic examination disclosed cystic spaces lined by abundant clear and eosinophilic tumor cells with pleomorphic nuclei. Differential diagnosis included primary ovarian oxyphilic-type clear cell carcinoma and sex-cord tumor with extensive luteinization. However, analysis of the patient's past history revealed that in 2003, she had undergone nephrectomy for a papillary renal cell carcinoma, and a histological comparison between the primary and the present tumor exhibited in the latter a substantially larger number of clear cells and loss of papillary architecture. Immunohistochemistry demonstrated a characteristic renal immunophenotype for a type II tubulopapillary tumor metastatic to ovary. The tumor cells were strongly positive for CD10 and AMACR, and negative for cytokeratin 7. This confirmed the renal origin of the ovarian tumor despite its divergent morphology of the renal primary. This is the first reported case of ovarian metastases of type II tubulopapillary carcinoma of the kidney.