Challenges in peri-aortic paraganglioma management

Abstract

Introduction

Paragangliomas are rare neuroendocrine tumors that constitute 15%–20% of all chromaffin cell tumors. Majority of these tumors are located in head and neck region, typically along the glossopharyngeal and vagus nerves. In contrast, sympathetic paraganglia are predominantly located in the abdominal area, adjacent to the inferior hypogastric plexuses near the urogenital organs and urinary bladder. Rarely, they present at unusual sites like peri-adrenal, para-aortic, inter-aortocaval, and para-caval retroperitoneal sites [1].

Retroperitoneal paragangliomas are very rare with only few cases reported in the literature [2]. Due to their vascular nature and their close proximity to the great vessels, complete surgical resection of these tumors is often difficult [3]. Surgical resection of these tumors are complicated with intraoperative bleeding and catecholamine crisis. We report a challenging case of retroperitoneal peri-aortic paraganglioma, the surgery was challenging due to close adhesion to celiac artery, hepatic artery, portal vein (PV), and inferior vena cava (IVC).

Case report

A 71-year-old man was incidentally found to have an intra-abdominal mass on ultrasound while being evaluated for low back and leg pain. Lab work showed elevated urinary metanephrine—3597 (45–290 μg/24 hr) and nor-metanephrine levels—3036 (82–500 μg/24 hr). Computed tomography (CT) contrast of the abdomen and pelvis reported a large heterogeneous 7 cm aortocaval mass in the right upper quadrant (RUQ), displacing the IVC laterally, and the aorta medially (Fig. 1). Metaiodobenzylguanidine scan reported focal avid uptake in the region of right suprarenal fossa corresponding to the known mass in this region, most suggestive of pheochromocytoma. No additional abnormal areas of radiotracer uptake to suggest metastases. An fluorodeoxyglucose (FDG) – positron emission tomography (PET) scan showed a hilar mass, which was identified as non-small cell lung carcinoma through fine needle aspiration.

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Management

First Exploratory Laparotomy (Aborted)—Radiation—second Exploratory laparotomy (tumor excised)—chemotherapy.

First exploratory laparotomy

Initial attempt to remove the paraganglioma was aborted due to patient’s hemodynamic instability. The patients’ blood pressure was optimized preoperatively with alpha blocker prazosin, beta blocker bisoprolol and a tyrosine inhibitor metyrosine.

Radiation SBRT

After adequate mapping with CT, simultaneous radiation for both paraganglioma (SBRT—2500 cGy in 5 fxn) and early-stage lung cancer (SBRT 5000 cGy in 5 fxn). However, CT after the conclusion of radiotherapy showed no significant regression of tumor except peripheral necrosis. However, SBRT failed to shrink the paraganglioma.

Second exploratory laparotomy

Anesthesia plan

Preoperative thoracic epidural was placed and central line, and arterial line was inserted after general anesthesia was induced, and the patient intubated in the operating room.

Surgical procedure

The patient abdomen and chest were prepped fully in case he needed a cardiac bypass. The abdomen was opened through the previous Mercedes Benz incision, and the peritoneum was opened carefully. Adhesions from previous surgery were taken down with sharp and blunt dissection. Thompson retractors were applied. Kocherization of the duodenum and full mobilization of the right lobe of the liver was performed. To get control of the infrahepatic and suprahepatic vena cava, the cava was encircled and umbilical tapes were placed, then encircled the left renal vein. The porta hepatis was also encircled for possible control. The tumor was very carefully away from the crus of the diaphragm. Dissection started on the left side of the tumor and tumor was dissected away from the celiac artery and the hepatic artery, the PV, as the tumor was noted to be adherent to the PV. The tumor was dissected from lateral to medial site and mobilized circumferentially and the tumor was just attached only to the vena cava. At this time, vascular surgeon scrubbed in, and with his help tumor was dissected away from the vena cava. Of note, the tumor was also adherent to the left renal vein and left adrenal, which was dissected completely. Once the tumor was removed, hemostasis was maintained. All the vessel loops and umbilical tape encircling the cava, the PV, and the left renal vein were removed, hemostasis was maintained. The abdomen was closed in layers. Blood loss was approximately 300–400 cc. Once the tumor was removed, the patient was started on vasoconstrictive agents.

Microscopic evaluation showed multiple tumor nests with zellballen architecture, and uniform immunopositivity for synaptophysin and chromogranin with a 4%–6% Ki-67 mitotic index consistent with a paraganglioma (Fig. 2).

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Chemotherapy, outcome, and follow-up

In our patient, although the tumor was in close contact with the AA and IVC, the resection was complete. Postoperatively, the patient completed 4 cycles of chemotherapy (carboplatin) for his lung cancer. Four years after surgery, the patient continues to undergo regular physical and morphological examinations, and there is no indication of either loco-regional recurrence of paraganglioma or distant metastasis.

Discussion

Paragangliomas are neuroendocrine neoplasms derived from paraganglia of the autonomic nervous systems. While most of these tumors present as palpable masses in the neck, retroperitoneal paragangliomas are exceedingly rare with only few cases reported in the literature. Majority of these retroperitoneal paragangliomas are symptomatic. However, the absence of typical triad of sweating, headache, and fluctuating hypertension makes preoperative diagnosis difficult. Urinary metanephrines and nor-metanephrines levels are the most sensitive tests that aid the diagnosis. Also, imaging with CT/MRI can detect these extra-adrenal tumors. On MRI, these tumors appear with intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images [4].

Complete surgical resection is the mainstay of management [5]. Surgical management can be challenging due to tumor location, especially when a tumor invades or lies near great vessel. High intraoperative high mortality is attributed to sudden hypertensive crisis due to catecholamine release during tumor resection and bleeding due to the vascular nature of these tumors. Preoperative alpha- and beta-adrenergic blockades minimize the risk of an intraoperative hypertensive crisis.

There are only few reported cases of para-aortic paraganglioma invading the aorta and IVC which required vessel resection and grafting [6]. Meticulous surgical technique and careful dissection of the tumors adherent to the vessels is required. In our present case, the tumor was adherent to hepatic artery and IVC, which was successfully dissected away from the vessels.

Definitive diagnosis is confirmed with histological findings. Although paragangliomas are usually benign, more than 20% of the abdominal paragangliomas are malignant. It has also been reported that the incidence and prevalence of malignant paragangliomas are higher in patients with SDHB mutation. Malignancy can only be confirmed by local invasion of surrounding structures at the time of resection or the presence of metastases [7]. The effectiveness of chemotherapy remains uncertain and is generally restricted to patients with locally advanced or metastatic disease that cannot be treated surgically or respond to radionuclide therapy, as was the case with our patient. Paragangliomas are more likely to recur when compared with pheochromocytoma, hence a lifelong follow up is required.

Conclusion

This was a challenging case of paraganglioma with an unusual location. Due to its favorable outcome, surgical resection should be attempted even if the paraganglioma is in close contact with the great vessels.

Conflicts of interest

None declared.

Funding

None declared.

References