Giant retroperitoneal lymph node—an uncommon presentation of duodenal neuroendocrine tumour

Abstract

Primary retroperitoneal neuroendocrine tumours (NETs) are extremely rare, and many a times, these are metastatic lesions with known or unknown primary location, most commonly arising from the stomach, duodenum, small intestine and rectum. NETs arising from the duodenum are more commonly seen in the first part of the duodenum followed by the second part. The incidence is increasing because of easy accessibility to endoscopies and cross-sectional imaging. In NETs, lymph node (LN) metastasis occurs commonly when the tumour size is more than 2 cm. In contrast, LN metastasis occurs even with subcentimetric lesions, especially the ampullary variant of NETs. A patient presented to us with mild abdominal pain and found to have retroduodenal mass. On evaluation found to be a metastatic LN deposit of NET with the primary arising from the first part and supra-ampullary part of duodenum.

Background

Neuroendocrine tumours (NETs) most commonly present in the gastrointestinal tract (67%), followed by the bronchopulmonary system (25%).¹ Primary retroperitoneal NETs are extremely rare, and most of the time, these are metastatic lesions with a known or unknown primary location. Duodenal NETs are rare, with an estimated incidence of 1%–3% of all duodenal tumours.² The incidence of duodenal NETs has risen over a while because of the easy availability of endoscopy and the increasing use of cross-sectional imaging.³ Duodenal NETs are more common in the first part of the duodenum (D1), followed by the second part of the duodenum (D2). In NETs, most of the time, lymph node (LN) metastasis occurs when the tumour size is more than 2 cm. In contrast, in duodenal NETs, LN metastasis occurs even with <1 cm of size, especially with the ampullary variant of NETs.⁴ Here we present a case report of duodenal NET with a large retroperitoneal LN mass at index presentation and discuss the challenges we faced in the management of this patient.

Case presentation

A 59-year-old man with a history of 20 pack-years of smoking, known hypertensive and coronary artery disease, who underwent percutaneous angioplasty 2 years before, presented with upper abdominal pain. Physical examination revealed a single palpable non-tender lump in the right hypochondrium with no associated hepatosplenomegaly and no other abdominal mass. Abdominal ultrasonography showed a hypoechoic lesion of approximately 7.2×8.6 cm retroduodenal region suggestive of a non-functional pheochromocytoma or a paraganglioma. The 24-hour urine metanephrine level was normal. A contrast-enhanced computed tomography of the abdomen showed a well-defined retroduodenal soft tissue lesion of around 5.1×8.4×10.1 cm, anterosuperior to the upper pole of the right kidney, abutting the segment VI of the right liver lobe, inferior vena cava, displacing the C loop of duodenum anteriorly and has ill-defined fat planes with the duodenum (figure 1A). MRI of the abdomen did not reveal any additional information over the previous CT performed.

Figure 1.

(A) Axial image depicting well-defined hypodense lesion retroduodenal lymph nodal mass. (B) Endoscopic view of duodenum showing submucosal lesion with central umbilication. (C) Resected specimen of the distal stomach and proximal duodenum along with lymph nodal mass. (D) Cut section resected specimen showing submucosal nodule in proximal duodenum (solid white arrow).

An upper GI endoscopy was performed in view of described loss of fat planes with the duodenum. It revealed multiple small submucosal nodules at D1 and supra-ampullary D2. However, the ampulla could be separately identified away from the visible submucosal nodules (figure 1B). Endoscopic ultrasonography (EUS) was performed for further evaluation of the nodules and a fine-needle aspiration cytology was performed from the largest nodule in the first part of duodenum under the EUS guidance which revealed a well-differentiated NET.

DOTATATE PET revealed a somatostatin receptor-expressing multiple lesions largest 2×2 cm in the duodenum likely primary and another lesion at the right para-caval region, mostly LN metastasis. There was no evidence of uptake in any other site. Ultrasound neck was done to assess the thyroid status in suspicion of Multiple Endocrine Neoplasia (MEN) syndrome, which showed no features suggestive of medullary carcinoma or parathyroid hyperplasia. The patient was diagnosed with a duodenal NET with retroperitoneal LN metastasis.

The patient was planned for surgery. Preoperatively, the options of pancreaticoduodenectomy and the segmental resection were discussed in view of multiple comorbidities and poor performance status (ECOG 2). The patient was very reluctant to undergo a more morbid procedure like pancreaticoduodenectomy. So planned for distal gastrectomy and segmental resection of the duodenum. On exploration, there was a 12×8×6 cm size, large encapsulated tumour in the retroduodenal region, anterior to right kidney abutting inferior vena cava and posterior to the head of pancreas. There is palpable intraluminal nodularity felt in the first part of duodenum and supra-ampullary part of D2. No liver, omental and peritoneal deposits were noted. Distal gastrectomy and segmental duodenal resection (D1 and supra-ampullary part of D2) and resection of the retroduodenal mass was performed. On cut section, multiple nodules were noted in D1 and supra-ampullary part of D2 and distal stomach with overlying mucosa appearing normal (figure 1C, D). Restoration of digestive tract continuity was achieved by an end-to-end gastroduodenal anastomosis.

On histopathology examination, Duodenal nodules on microscopic examination showed small-to-medium size, monomorphic with round nuclei, which were arranged in a trabecular and organoid pattern, extended up to muscular propria. Lymphovascular tumour emboli was present. Proximal gastric resection margin was free of tumour and distal duodenal margin involved with tumour. On immunohistochemistry, tumour cells positively stained with synaptophysin and chromogranin. Overall histopathology report was suggestive of primary duodenal NET with retroduodenal LN metastasis (figure 2).

Figure 2.

(A) Metastatic tumour deposits were seen in the locoregional lymph nodes dissected from the attached mesentery (200×, H&E). (B and C) The larger mesenteric mass (sent separately) showed large central areas of haemorrhage. The periphery of the mass showed preserved nodal architecture, which was largely replaced by a morphologically similar tumour (100× and 400×, H&E). (D) Inset shows the Ki67 index, which is 1%.

The postoperative course was uneventful, and the patient was discharged on postoperative day 11 in a stable condition.

Outcome and follow-up

At 6 months postsurgery, patient was asymptomatic and currently doing well. He was advised to be under close follow-up in view of microscopic involvement of distal margin.

Discussion

NETs of the duodenum are rare, with an overall incidence of 1%–3% of all primary duodenal tumours. The common age at presentation is the sixth decade with slight male predominance.¹ The most common location of duodenal NETs is D1, followed by D2, D3 and D4, respectively.⁵ Lasson et al in their case series of duodenal NETs noted that 61% were located in D1, while in another study by 93% were found in the D1/D2 region.⁶ The majority (90%) of duodenal NETs are non-functional. Presentation of duodenal NETs are mostly asymptomatic and diagnosed incidentally on imaging or endoscopy performed for other indications. If presented with symptoms, the clinical presentation may vary with the location of a tumour in the duodenum; abdominal pain being the most common presenting symptom (80%) followed by diarrhoea (73%), dyspepsia (59%), bleeding (32%); but ampullary NETs most commonly present with jaundice (60%) followed by abdominal pain (40%).⁷ In our index case, the patient presented with abdominal pain.

Diagnosis and localisation of NETs are difficult because of their size, location and rarity. In duodenal NETs, cross-sectional imaging (CT and MRI) fails to localise in >80% of patients.⁸ However, preoperative imaging is beneficial in evaluating the local invasion and the metastatic lesions in the abdomen. Somatostatin receptor scanning has better sensitivity for localisation of duodenal NETs than other conventional imaging techniques.⁹ Similarly, in our case, preoperative imaging with CT and MRI failed to localise the primary lesion but revealed a loss of fat planes of the lymph-nodal mass with the duodenum.

At presentation, most of the duodenal NETs have metastases to regional LNs because most of the duodenal NETs are non-functional and are of small size. The incidence of LN metastasis in resectable ampullary NET and duodenal NETs was around 72% and 48%, respectively.¹⁰ More than 2 cm of primary NETs is considered a risk factor for metastasis, so radical surgery is the treatment of choice. In <2 cm NETs, treatment of choice is still debatable between endoscopic resection versus surgery because some studies reported LN metastasis (8%–13%) occurring even with <1 cm duodenal NETs.¹¹ The European Neuroendocrine Tumours guidelines recommended endoscopic resection for <1 cm tumours without the periampullary and ampullary region involvement. LN metastasis was significantly associated with tumours measuring >1 cm or invading beyond the muscularis propria or lymphovascular invasion.¹² In our case, the patient had 2×2 cm primary duodenal NET at D1 and proximal D2 with single large retro-duodenal LN metastasis.

We performed distal gastrectomy with D1 and supra-ampullary D2 resection with large 12 cm lymphatic metastasis adjacent and anterior to the right kidney owing to the clinical limitations in this patient. Postoperative histopathology report revealed a well-differentiated low-grade NET with microscopic involvement of the distal margin (R1 resection). However, according to a study by Untch et al, tumour size and tumour grade were identified as being associated with recurrence, but not intervention type, LN metastases, ampullary location, or margin status.¹³

In patients with liver metastasis and unresectable tumours, synthetic analogues of somatostatin should be considered as they stabilise the disease and reduce the growth of metastasis. However, cytoreductive surgeries may improve survival.¹⁴

Learning points.

• Surgical resection is crucial in the management of duodenal NETs.

• In low-grade and intermediate-grade tumours, local resection can be a feasible approach in patients with comorbidities.

• R1 margins in low-grade and intermediate-grade tumours do not have statistical significance on overall survival.

Ethics statements

Patient consent for publication

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