Primary renal neuroblastoma metastasizing into liver and lungs with tumor thrombus extension into the right atrium.

Neuroblastomas are malignant tumors of the sympathetic nervous system. Areas of manifestation most commonly involve the abdomen, neck, thorax and pelvis. Primary renal neuroblastomas are extremely rare, only a few case reports exist worldwide, and even those are discussed controversially.We present the case of a 6-year-old girl with a renal tumor and a tumor thrombus extending into the right atrium, which radiologically appeared to be a Wilms tumor. Since the lesion did not respond to nephroblastoma-specific therapy, a biopsy from one of the liver metastases was taken, revealing the revised diagnosis of a clear cell renal cell carcinoma. Histopathology of the reference center, however, described a primary renal neuroblastoma. After adjusting the chemotherapy tumornephrectomy including the complete venous thrombus could be performed without any complications.Neuroblastoma originating from a kidney is an absolute rarity that can easily be misdiagnosed as Wilms tumor, especially, if a typical tumor thrombus with extension into the inferior vena cava is seen. Therefore neuronspecific enolase in serum as well as vanillylmandelic acid and homovanillic acid in the urine should be determined in all patients when Wilms tumor is assumed. To the best of our knowledge, this is the first published case of a primary renal neuroblastoma with a tumor thrombus extending into the right atrium.