Atypical CT findings of renal neuroblastoma: a case report

Abstract

Background: The neuroblastoma (NB) is a highly malignant tumor of the ectoderm of sympathetic nerve cells and one of the most common malignant tumors in children, which can occur in any part of the sympathetic nerve plexus distribution, however it is less common in the kidney.

Case description: Here we present a case of a 4-year-old boy who came to our hospital for medical help because of "abdominal distension for 1 day". Abdominal computed tomography (CT) revealed a huge retroperitoneal soft tissue mass with unclear boundaries with kidneys and adrenal glands, and low-density cystic necrosis areas were seen in the tumor. Contrast-enhanced scan showed that the mass showed mild heterogeneous enhancement. Based on these findings in the patient, he was initially considered to have Wilms tumor, but was finally pathologically confirmed as renal NB. The purpose of this article is to provide the clinicopathological features and CT manifestations of renal NB, and to discuss its differential diagnosis with other renal tumors, in order to better provide clinicians with a better understanding of the rare solid tumor. The renal NB is usually a large lobulated soft tissue mass with unclear boundary and incomplete capsule, which is prone to hemorrhage, necrosis, cystic degeneration and calcification. On CT, the mass is usually isodensity or slightly hypodense, and the cystic degeneration and necrosis area is hypodense, and on contrast-enhanced scan, it can be mildly to significantly enhanced, but the cystic degeneration and necrosis area have no enhancement.

Conclusions: The CT findings of our case were atypical and overlapped with those of Wilms, so our case suggests that renal NB should be considered as one of the differential diagnoses of Wilms, the most common malignancy of the kidney in children.

Keywords: Renal; case report; computed tomography (CT); nephroblastoma; neuroblastoma (NB).

Figure 1

Abdominal CT scan image of patient before treatment. (A) Intravenous urography showed that the left kidney shadow increased, the density increased, and the left renal pelvis, kidney, and upper part of the ureter were compressed to the lower part (arrow). (B) CT unenhanced scan: a large soft tissue mass (about 25 cm × 18 cm × 21 cm) was observed in the left retroperitoneum, with uneven density and unclear boundaries between the lesion and the left kidney and adrenal gland. A low-density cystic lesion (black arrow) was also observed in the tumor. (C) Contrast-enhanced cortical phase: the lesion presented mild heterogeneous enhancement. Vessels are visible in the mass (white arrow), and there is no enhancement in the necrotic area of the cyst (black arrow). The pancreas, spleen, and surrounding intestine were significantly compressed and shifted to the right. (D) Medullary phase of enhanced scan: the lesion exhibited continuously inhomogeneous enhancement and was clearly demarcated from the remaining renal parenchyma. Vessels are more visible in the mass (white arrows), and there is still no enhancement in the necrotic area (black arrows). CT, computed tomography.

Figure 2

Histopathological features and immunohistochemical staining of renal neuroblastoma. Hematoxylin-eosin staining: pathological sections showed small round or oval tumor cells with uniform diffuse distribution (A). Immunohistochemical staining with antigen demonstrated positive expression for CD56 (B), NSE (C), and Syn (D). CD56, neural cell adhesion molecules; NSE, neuron-specific enolase; Syn, synaptophysin.

Figure 3

PET/CT examination of the patient at 2 years postoperatively showed that there was a soft tissue mass with high metabolism in the left retroperitoneum. (A) Maximum intensity projection; (B) axial CT; (C) axial PET; (D) axial PET/CT fusion. The black arrows show metastases in the left retroperitoneum. PET, positron emission tomography; CT, computed tomography.