Ductal cell carcinoma of the kidney with extensive signet ring cell mucosecreting areas. A case report with immunohistochemical analysis.

We present the case of a 45-year-old patient with a renal ductal cell carcinoma arising in the Bellini ducts that was composed of histologically well-differentiated tubulopapillary and cystic areas with desmoplastic stroma, extensive mucosecreting areas, and regions depicting a transition between these two constituents. The mucosecreting component was mostly formed by signet ring tumor cells containing cytoplasmic Alcian blue-PAS-stainable mucins. The tubulopapillary and cystic areas of the tumor showed the immunohistochemical staining for low and high molecular weight cytokeratin, EMA, vimentin and Ulex europaeus, characteristic of ductal cell carcinoma. The mucosecreting cells also presented intense positive staining for cytokeratin and vimentin, and this is quite similar to observations reported in some forms of gastrointestinal cancer with rhabdoid features that are indicative of poor prognosis. Our findings suggest that mucosecreting areas with signet ring cells represent an extreme metaplastic change that can seldom occur in certain forms of renal tumors.