Combination of clear cell renal cell carcinoma with well-differentiated neuroendocrine tumor of the kidney

Abstract

We present a rare combination of two tumors (clear cell renal cell carcinoma with well-differentiated renal neuroendocrine tumour) in a 67-year-old man. To the best of our knowledge, English literature presents only one similar clinical case and we are the first to describe this tumor combination in Russian. The renal tumor was discovered accidentally on abdominal ultrasound. The patient had neither complaint, nor clinical signs of carcinoid syndrome, nor tumours in his medical history. CT scan showed a heterogeneous tumor, being 35×35×30 mm in size. It was in the upper segment of the left kidney, deforming the contour of the kidney, without renal pelvis expansion. We performed nephrectomy using the da Vinci Surgical System. The postoperative period was uneventful; no complications were reported. Macroscopically the tumour presented as a round encapsulated node of a variegated structure. Microscopic examination showed that the tumor consisted of large cells with clear cytoplasm and monomorphic small round nuclei (nucleoli were determined at ×400). In some regions of the tumor, we detected small polygonal cells, with ovoid nuclei with granular chromatin, forming solid, ribbon-shaped structures and spindle-cell patterns. The neuroendocrine component revealed strong expression of chromogranin A, synaptophysin, CD56, S-100, pancytokeratin, and СK7. Histological and immunohistochemical studies, we diagnosed a combination of clear cell renal cell carcinoma (Grade I–II by Fuhrman classification) and renal neuroendocrine tumour (Grade I), pT1aN0. The size of the neuroendocrine component was of 7×3 mm; the index of proliferation Ki-67 was less than 1.0%; and the mitotic index was less than 2 ×10 HPF. After nephrectomy this patient needed close monitor because renal neuroendocrine tumours are very rare and have a higher malignant potential than renal cell carcinoma. Keywords: urological pathology, kidney tumor, clear cell renal cell carcinoma, neuroendocrine tumor, immunohistochemistry