Histopathological classification of nephroblastomas in slaughtered swine.
A histological classification of 74 nephroblastomas found in slaughtered swine is reported. The tumours were classified into 4 main types; nephroblastic (29 cases); epithelial (38 cases); mesenchymal (one case), and miscellaneous (6 cases), on the basis of their histological characteristics and especially on their relative contents of epithelial and mesenchymal elements. The nephroblastic type was further divided into 3 subtypes: nephroblastic only (one case), nephroblastic predominance 13 cases) and nephroblastic equal to epithelial (15 cases). Similarly, the epithelial type was classified into two subtypes: epithelial only (one case) and epithelial predominance (37 cases). The histological features of these tumours were compared with those of human nephroblastoma. The classification of swine nephroblastomas made in this study closely resembles that of human tumours. Two examples of the nephroblastic type were metastasized but none of the other types.