What is the most likely diagnosis and recommended management for a 7 × 9 × 10 cm well‑defined hypoattenuating retroperitoneal mass in the upper abdomen that displaces the pancreas, inferior vena cava, and left hepatic lobe, encircles the celiac axis, superior mesenteric artery, and both renal arteries, contains calcifications, shows heterogeneous post‑contrast enhancement, and lacks aggressive bony involvement, lymphadenopathy, or distant metastases?

Retroperitoneal Ganglioneuroma: Diagnosis and Management

Most Likely Diagnosis

The imaging characteristics strongly favor a benign ganglioneuroma rather than neuroblastoma or ganglioneuroblastoma, given the well-defined margins, lack of aggressive local invasion, absence of lymphadenopathy, and no distant metastases despite the large size 1.

Key Diagnostic Features Supporting Ganglioneuroma

• Well-defined regular margins with hypoattenuating appearance on CT distinguish this from malignant neuroblastic tumors, which typically demonstrate irregular, infiltrative borders 1
• Calcifications are present in approximately 20-30% of ganglioneuromas and do not indicate malignancy in this context 1
• Heterogeneous post-contrast enhancement reflects the mixed cellular composition of mature ganglion cells and Schwann cells typical of ganglioneuroma 1
• Vascular encasement without occlusion (celiac axis, SMA, renal arteries) represents displacement rather than invasion—a critical distinction favoring benign pathology 1
• Absence of lymphadenopathy and metastases strongly argues against neuroblastoma or ganglioneuroblastoma, which would be expected with a 10 cm mass if malignant 1

Differential Diagnosis Considerations

While the imaging favors ganglioneuroma, other retroperitoneal masses must be excluded:

• Pancreatic neuroendocrine tumor (NET): However, NETs typically show strong arterial enhancement and arise from the pancreas itself, not displacing it anteriorly 1
• Retroperitoneal sarcoma: Liposarcomas and other sarcomas can reach large sizes, but typically show more aggressive features including organ infiltration rather than displacement 1, 2
• Paraganglioma: Can present as retroperitoneal mass with vascular encasement, but typically demonstrates intense arterial enhancement and may cause hypertensive episodes 3

Essential Pre-operative Workup

Before proceeding to surgery, the following evaluations are mandatory:

Biochemical Assessment

• 24-hour urine catecholamines and metanephrines to exclude functional paraganglioma, even though ganglioneuromas are typically non-functional 1, 3
• Elevated catecholamines would necessitate alpha-blockade with phenoxybenzamine (initially 10 mg twice daily, increased every other day to 20-40 mg 2-3 times daily) for 10-14 days pre-operatively 4, 3

Tissue Diagnosis

• CT-guided core needle biopsy is NOT routinely recommended for suspected ganglioneuroma when imaging characteristics are typical and surgical resection is planned, as biopsy rarely changes management and carries risk of hemorrhage given the vascular encasement 1
• Biopsy should be reserved for cases where imaging is atypical, patient is not a surgical candidate, or neoadjuvant therapy is being considered 1

Advanced Imaging

• MRI with T2-weighted sequences can provide additional characterization—ganglioneuromas typically show high T2 signal due to myxoid stroma 1
• Somatostatin receptor scintigraphy (SSRS) may be considered if NET remains in the differential, though the displacement of pancreas rather than origin from it argues against this 1

Recommended Management Strategy

Complete surgical resection is the definitive treatment and only curative option for retroperitoneal ganglioneuroma 1.

Surgical Approach

• En-bloc resection with involved organs may be necessary given the extensive vascular encasement of celiac axis, SMA, and renal arteries 1, 2
• Vascular reconstruction capability must be available intraoperatively, as dissection from encased vessels may require arterial repair or bypass 2, 5
• Multivisceral resection (potentially including pancreatic head, portions of liver, or kidney) should be anticipated if the tumor cannot be separated from these structures without leaving positive margins 1, 2
• Intraoperative frozen section is essential to confirm benign histology and guide extent of resection 3

Critical Surgical Pitfalls to Avoid

• Do not attempt piecemeal resection—complete en-bloc removal is essential even for benign ganglioneuroma to prevent local recurrence 1, 2
• Avoid excessive manipulation before vascular control is obtained, particularly given the extensive vessel encasement 2, 5
• Prepare for significant blood loss—cross-match adequate blood products and consider cell-saver technology 2

Prognosis and Follow-up

• Ganglioneuromas have excellent prognosis with complete surgical resection, with recurrence rates <5% when negative margins are achieved 1
• Post-operative surveillance with CT imaging at 3-6 months, then annually for 5 years is reasonable to detect rare recurrence 1
• No adjuvant therapy (chemotherapy or radiation) is indicated for completely resected ganglioneuroma 1

If Malignancy is Discovered

Should intraoperative frozen section or final pathology reveal neuroblastoma or ganglioneuroblastoma rather than ganglioneuroma:

• Complete surgical resection remains the primary treatment even for malignant neuroblastic tumors 1
• Adjuvant chemotherapy would be indicated for ganglioneuroblastoma or neuroblastoma based on stage and risk stratification 1
• Radiation therapy may be considered for high-grade malignancy to reduce local recurrence, though benefit on overall survival is unproven 1