Stromal-type Nephroblastoma with or without Anaplasia in Two Hedgehogs (Atelerix albiventris)

We describe the clinical and histological characteristics of stromal-type nephroblastomas that developed in two hedgehogs (Atelerix albiventris). In case 1, the tumour was composed of a proliferation of anaplastic stromal cells with ductal structures resembling the epithelium of nephroblastoma. In case 2, spindle-shaped cells that were somewhat larger than nephroblasts were frequently seen surrounding the cell cluster, and there was proliferation of stromal cells with collagen fibres at the periphery. Immunohistochemically, the tumour cells labelled weakly to strongly for the nephroblast marker Wilms' tumour-1 and were positive for Ki67 with rates of 5% and 10% for cases 1 and 2, respectively. Based on the above, the diagnosis was of stromal-type nephroblastoma with anaplasia in case 1 and without anaplasia in case 2. Our findings suggest that stromal-type nephroblastomas arise in adult hedgehogs and are clinically benign, and that histological anaplasia does not affect the prognosis.