RESUMEN
Chromophobe renal cell carcinoma was described by Thoenes et al. in 1986, and associations with carcinoma of collecting ducts, conventional renal cell carcinoma and sarcomatoid renal cell carcinoma have been described. We report a case of chromophobe renal cell carcinoma which showed neuroendocrine differentiation. This is the first known case to be clearly identified as such. The patient was a 56-year-old man with constant right flank pain and hematuria; CT scan revealed an 8.5 cm nonhomogeneous mass involving the right kidney. Right radical nephrectomy was performed. The tumor showed a mixture of classical and eosinophilic patterns of chromophobe cell carcinoma. Additionally, it showed insular, glandular and rosetoid-like formations embedded in a dense eosinophilic hyaline stroma. The cells were cuboid or cylindrical with well-defined boundaries, finely stippled chromatin and a small nucleolus. The appearance of the cytoplasm varied from faintly eosinophilic to coarsely granular eosinophilic. Immunohistochemically, the neuroendocrine areas were reactive for C-kit, epithelial membrane antigen, cytokeratin, cytokeratin 7, chromogranin A, neuron-specific enolase, CD56 and S-100 protein. Our case represents a typical chromophobe carcinoma with neuroendocrine differentiation. Additionally, the immunohistochemical profile in both types of lesion suggests a common origin from renal tubular cells.