Nephroblastoma is the most common primary renal neoplasm of swine and man. This report describes a swine nephroblastoma localized at the caudal pole of the left kidney, extending to the renal hilum which, on light microscopy, showed unusual mucus-producing epithelial cells of many tubules. The presence of intracytoplasmic mucin was confirmed by PAS-diastase positivity and alcianophilia both at pH 2.5 and at 1.0. Mucin-producing cells revealed cytokeratin 19 and pankeratin AE1/AE3 positivity, and some of them a chromogranin A immunohistochemical positivity; they were also positive for Grimelius stain. In veterinary medicine, even if the occurrence of mucus-producing cells in nephroblastoma has rarely been observed, this is the first description of a case of swine nephroblastoma with mucus-producing cells positive for neuroendocrine markers, thus a neuroendocrine origin was suspected.

Key words: Kidney, Mucin-producing cells, Nephroblastoma, Neuroendocrine, Swine