A 13 year old, intact female, Siberian husky was presented to a private veterinary practitioner at Rudge Ramos (São Paulo). At that time, the patient showed signs of anorexia, weight loss, lethargy and urinary incontinence. Physical examination revealed a palpable midabdominal mass and edema of the posterior limbs. A complete blood cell count revealed a normocytic and normochromic anemia (hematocrit 28%) and urinalysis was within normal limits except for bilirubinuria. A serum biochemical profile was normal, aside from a mild elevation in liver enzymes. Abdominal ultrasound examination was performed and revealed 11.50cm X 9.93cm solid with mixed echogenicity mass encircling the abdominal aorta, displacing dorsally the cranial pole of the left kidney. The caudal vena cava coursed the dorsal aspect of the mass and the lumen of the vein cranial to the renal veins was partially occluded by a 6.33 X 3.44 firm mass with shadowing lesions within its parenchyma (parenchymal calcification). Doppler ultrasound identified an arterial flow of low resistive index in this mass suggesting a neoplastic invasion of the caudal vena cava. Intrahepatic shunts were observed within the hepatic parenchyma, suggesting portal hypertension. Peritoneal effusion was also verified. The cytological analyses of the mass suggested a neoplasia with neuroendocrine origin. The patient was euthanized and submitted to necropsy and confirmed the lesions observed in the ultrasonographic examination. The histopathologic diagnosis suggested an undifferentiated carcinoma, and was required an immunohistochemical staining analyses. On immunohistochemical staining, tumor cells stained positively for neuroendocrine cell markers, such as chromogranin A and neuron specific enolase (NSE); and were negative for S-100, AE1AE3, CD99, vimentin, 35BH11, and adrenocorticotropic hormone (ACTH). Based on histological aspects and immunohistochemical features (the lack of staining for S-100), supported a diagnosis of adrenal neuroblastoma. Neuroblastoma is a tumor of ganglion cell origin that derives from primordial neural crest cells, which are the precursors of the sympathetic nervous system. It is one of the most frequently diagnosed neoplasms of children and infants, although they are rare in domestic animals. In literature it has been described in young dogs under three years of age. In this case the dog was mature. In humans and dogs, both primitive and differentiated neuroectodermal tumors, including pheochromocytomas, show variable positive staining for synaptophysin, chromogranin A, neurofilament, and NSE. Neuroblastomas are difficult to differentiate on the basis of routine cytologic examination or hematoxylin and eosin stained sections. Identification often requires special immunohistochemical and electron microscopic investigations.