Mesoblastic nephroma in a young Entlebucher Mountain Dog

An intact 16-month-old female Entlebucher Mountain Dog in poor general condition was presented with clinical signs of gastrointestinal disease. Abdominal ultrasonography revealed a mass in the right kidney. Nephrectomy combined with ovariohysterectomy was performed. Histology revealed a mesenchymal tumour that was composed of neoplastic spindle cells forming interlacing fascicles, whorls and bundles, and embedded into a loose myxoid to dense collagenous stroma. Immunohistochemically, neoplastic cells diffusely labelled for vimentin and partially for S-100 protein and p75^NTR. Based on these results, the tumour was diagnosed as a classical variant of a congenital mesoblastic nephroma. The expression of p75^NTR has not been described in this tumour entity before and its significance with regard to tumour promoting or tumour suppressing function or indication of a neurogenic differentiation remains undetermined. After a 3-year follow-up the dog was clinically healthy, indicating a successful surgical treatment.