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A case of metastatic adenocarcinoma from an unknown primary involving the aortic bifurcation

Aortic malignant neoplasms are rare; these may be primary or secondary (metastatic). Increasing use of cross-sectional imaging has allowed better detection and diagnosis of these conditions. We encountered a young woman presenting with acute abdomen who was found on cross-sectional imaging to have a malignant tumor involving the aortic bifurcation. An en bloc excision of the tumor was performed, with distal aorta reconstruction using an aortoiliac Dacron graft; this was complicated with infection and graft occlusion, necessitating total removal and extra-anatomic bypass. A pathologic diagnosis of metastatic adenocarcinoma involving the aortic bifurcation, with an unknown primary, was made.

The aorta is a rare site for tumor deposition. However, this does not preclude the occurrence of primary and secondary aortic malignant neoplasms. Brodowski, 1 in 1873, reported the first case of an aortic malignant neoplasm, a fibrosarcoma of the thoracic aorta. Since then, there have been isolated case reports and case series of aortic malignant neoplasms in the literature. Metastatic tumors involving the aorta are relatively more common than primary tumors. In the thoracic region, these usually originate from the lungs, esophagus, and thymus; in the abdomen, germ cell tumors and tumors of retroperitoneal origin are commonly implicated. 2 Adenocarcinomas are tumors originating from glandular tissue, usually affecting the lungs, gastrointestinal tract, breasts, and thyroid gland. Metastasis to the aorta is very rare. We report a young woman encountered in our center, presenting with acute abdomen, eventually diagnosed with metastatic adenocarcinoma involving the aortic bifurcation, with an unknown primary.
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CASE REPORT
A 27-year-old woman with no underlying medical illness presented to our center with a 2-week history of progressively worsening abdominal pain associated with constipation and constitutional symptoms. There was no history of trauma or surgery. She was afebrile and normotensive, and her heart rate was

DISCUSSION
Aortic malignant neoplasms are rare clinical entities, with a multitude of clinical manifestations and imaging findings but no widely accepted consensus for operative intervention. Isolated case reports and case series have attempted to describe their various clinical presentations, imaging findings, and treatment strategies. To this day, evidence-based information for the most appropriate algorithm in management of these cases is still lacking. A case-by-case approach is most appropriate, at present.
Malignant neoplasms affecting the aorta may be either primary or secondary (metastatic). Of these two, secondary malignant neoplasms are more common. 2 Primary aortic malignant neoplasms more commonly affect men, with a male to female ratio of 2:1 to 5:1. The mean age is 60 years, and both thoracic and abdominal aortas are affected equally. 3,4 Because of the old age at presentation, imaging findings, when present, are commonly attributed to thrombosis and atherosclerotic disease. This contributes to the difficulty in early diagnosis. Secondary (metastatic) aortic malignant neoplasms are more commonly seen and are more readily diagnosed, possibly owing to the knowledge of a pre-existing primary tumor. There appears to be no age predilection. In the thoracic region, invasion from the lungs, esophagus, and thymoma is the usual scenario. 2 Retroperitoneal sarcomas and germ cell tumors are the most common malignant neoplasms invading the abdominal aorta, potentially with resultant aneurysm or pseudoaneurysm formation and rupture. [5][6][7] A wide spectrum of clinical manifestations may accompany aortic malignant neoplasms, regardless of whether the tumor is primary or metastatic. These include embolic events to the brain, lower extremities, and abdominal viscera manifesting as hypertension, intestinal infarcts, peripheral vascular disease, or acute abdomen. 2 Uncommonly, spontaneous aortic rupture with massive hemorrhage may occur; this has been reported in the literature. 8,9 The scarcity in the literature of metastatic carcinoma involving the aorta (Table) hampered us in terms of locating the primary tumor. The biopsy result and immunohistochemical staining suggesting a pancreatic origin led us to pursue structural and functional imaging to identify the primary tumor. The findings were normal. We postulated, after taking into account the possible pancreatic origin, that the tumor excised from the aortic bifurcation may have originated from either the aorta itself or, more plausibly, the gastrointestinal tract in the form of ectopic pancreatic tissue. When present, ectopia of the pancreatic tissue is mostly located within the gastrointestinal tract (70%-90% cases). 10 To this day, there is no consensus on the choice of oncologic intervention by chemoradiation. In this case, our patient received 28 fractions of radiotherapy, with combination chemotherapy with paclitaxel and cisplatin. After chemoradiation, CT during a period of 2 years at 4-to 6-month intervals showed stable disease, with no evidence of recurrence. Bohner et al 11 and Majeski et al 12 demonstrated in their experience that when limited metastasis or unresectable local recurrence is present, control with chemoradiation for a long period is possible.

CONCLUSIONS
Aortic malignant neoplasms are rare clinical entities with various clinical manifestations. Accurate diagnosis, followed by appropriate management, requires a multidisciplinary approach. Operative intervention, at present, is undertaken on a case-by-case basis. Our experience in managing this rare case of metastatic adenocarcinoma involving the aortic bifurcation is testament to the challenges involved in managing these rare surgical conditions.