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The Turkish Journal of Gastroenterology
2009, Volume 20, No 4, Page(s) 291-294
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A large functional somatostatinoma in the pancreatic tail: Atypical CT appearances
Ri-Sheng YU, Ying CHEN, Liu-Hong WANG, Xiu-Fang XU, Ding-Yao JIANG
Department of Radiology, Hangzhou, The Second Affiliated Hospital, Zhejiang University, School of Medicine, China
Keywords: Computed tomography, pancreatic neoplasms, somatostatinoma, liver neoplasms, endocrine tumors.
Summary
Somatostatinomas are extremely rare endocrine tumors, and those with diameters above 2 cm are reported to increase the risk of metastasis significantly. We report a case of a large functional somatostatinoma in the pancreatic tail without metastases. A 46-year-old woman with a history of recurrent mild upper abdominal pain and diarrhea for 10 months was admitted to our hospital. Multiple-phase spiral computed tomography revealed a 10 cm x 8 cm, ill-defined, elliptic mass in the body and tail of the pancreas. There was a slightly heterogeneous enhancement on hepatic arterial phase and isodensity to the pancreatic parenchyma with small dotted necrosis within the middle region of the mass on hepatic portal venous and parenchymal phase, with patent splenic vein, dilated collaterals at the splenic hilum and no dilated pancreatic duct, resembling a diffuse infiltration tumor. To the best of our knowledge, this is the first description of multiple-phase spiral computed tomography findings of a functional somatostatinoma in the pancreatic tail and the largest thus far on reported computed tomography, with some differences compared with the previous reports.
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  • Summary
  • Introduction
  • Case Presentation
  • Discussion
  • References
    • Introduction
    Somatostatinomas are extremely rare endocrine tumors that comprise around 1% of all gastroenteropancreatic endocrine neoplasms (1). Most somatostatinomas (56%) originate from the pancreas (2). The majority of patients (92.7%) with this tumor type are symptomatic and may present with the clinical somatostatinoma syndrome (1). Although there have been some reports describing the radiological characteristics of functional somatostatinomas (1, 3, 4), the imaging features with multiple- phase spiral computed tomography (CT) have not been addressed previously. We herein describe the multiple-phase spiral CT findings of a functional somatostatinoma in the body and tail of the pancreas in a 46-year-old woman, which after a literature review, appears to be the largest reported thus far.
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  • Summary
  • Introduction
  • Case Presentation
  • Discussion
  • References
    • Case Presentation
    A 46-year-old woman with a history of intermittent vague upper abdominal pain for 10 months was admitted to our hospital. The patient presented with mild persistent diarrhea, nausea, vomiting and jaundice. The laboratory tests indicated normal blood and urine amylase. The blood, urine, and regular stool tests also revealed no abnormality. The tumor markers showed carcinoma embryonic antigen 0.7 ng/ml (normal, <5 ng/ml), alpha- fetoprotein 4.0 ng/ml (normal, <20 ng/ml), and CA 19-9 3.8 U/m (normal, <37 U/ml). Chest X-ray was normal.
    An unenhanced spiral CT (Siemens Somatom Sensation 16, Germany) scan revealed a large, ill-defined, elliptic mass measuring 10 cm x 8 cm in the body and tail of the pancreas. The mass showed the same attenuation as the pancreatic parenchyma except for a small region of slightly low attenuation in the middle of the mass (Figure 1). Following intravenous administration of 100 ml of contrast medium at a rate of 3 ml/sec, the tumor revealed a slightly heterogeneous enhancement on hepatic artery phase (Figure 2) and isodensity to the pancreatic parenchyma with small dotted necrosis within the middle region of the mass on hepatic portal venous and parenchymal phase. Associated features included patent splenic vein, dilated collaterals at the splenic hilum, without dilated pancreatic duct (Figures 3A, 3B and 4), resembling a diffuse infiltration tumor. No metastases were detected in the extra-pancreatic region.
    Because there was no evidence of metastatic disease, localized pancreatectomy plus splenectomy were undertaken. Pathologic examination revealed a 10 cm x 10 cm x 6 cm somatostatinoma in the body and tail of the pancreas. Microscopic examination showed uniform cells in trabecular and packeting patterns with prominent vascularity, spindle and epithelioid tumor cells with “salt and pepper” nuclei, and rare mitoses (Figure 5). Immunohistologic staining was negative for smooth muscle actin, neurofilaments, insulin, gastrin, and serotonin, and positive for somatostatin (Figure 6).
    The patient’s postoperative course was uneventful, and she was discharged on the seventh postoperative day. At the 12-month follow-up, the patient was doing well and no longer had the upper abdominal symptoms or mild diarrhea.
  • Top
  • Summary
  • Introduction
  • Case Presentation
  • Discussion
  • References
    • Discussion
    Somatostatinomas are extremely rare endocrine tumors first described in 1977 (5). They derive from the somatostatin-producing delta cells of the pancreas or the endocrine cells of the digestive tract (6, 7) and may be sporadic (93.1%) or familial (6.9%) in association with neurofibromatosis type 1 (NF1), multiple endocrine neoplasia type 1 (MEN1), and Von Hippel–Lindau syndromes (8- 11). The estimated annual incidence is 1 in 40 million (12), with a median age at onset of 54 years. The tumor is malignant in 60–70% of cases (13), with tumor size being the most relevant predictive factor. A diameter of 2 cm is considered as the cutoff value, above which the risk of metastasis significantly increases (14, 15). Our case with a tumor size of 10 cm had no metastases in the extra-pancreatic region, which did not conform to the literature. Clinically, the classic somatostatinoma or inhibitory syndrome of this tumor type includes diabetes mellitus, diarrhea/steatorrhea, and cholelithiasis. Pathological examination of the surgical specimen provides the definitive diagnosis (1). The immunohistologic staining was positive for somatostatin in our case, and combined with the mild 'inhibitory' syndrome, the functional somatostatinoma was definitely diagnosed.
    On the basis of imaging descriptions from previous literature (16, 17), functional pancreatic islet cell tumors are usually small and subtle, with low inherent contrast. They are usually isodense with the pancreas on pre-contrast images and hyperattenuating in the hepatic arterial phase and become inconspicuous in the venous phase. However, only a few CT findings of pancreatic functional somatostatinoma have been reported previously (1, 7, 8). CT of the abdomen shows solid tumors of 3.5- 6 cm in diameter, some of which have calcification. The mass size in our case was 10 cm x 8 cm, which is the largest reported thus far. Contrast-enhanced CT shows nonhomogeneous enhancement of the pancreatic tumor with cystic areas of necrosis. To the best of our knowledge, the radiological manifestations of multiple-phase spiral CT of pancreatic functional somatostatinoma have not been described previously. The spiral CT findings of our case were a large, hypervascularized tumor within a small area of necrosis, resembling a diffuse infiltration tumor, and without calcifications or metastases, characteristics distinguishing this case from the previous reports.
    There are numerous differential diagnoses that should be considered when a pancreatic mass is detected without any hint of increased hormone release. Depending on the clinical history and the laboratory findings, the following diagnoses should be ruled out: diffuse infiltration tumor, e.g. pancreatic metastases, tuberculosis, and lymphoma; other pancreatic functional endocrine tumors, e.g. glucagonoma and vasoactive intestinal peptide- secreting tumor (VIPoma); non-secreting islet cell tumors; pancreatic adenocarcinoma; and focal pancreatitis. Glucagonomas and VIPomas should especially be excluded, because these two types of pancreatic functional endocrine tumors together with somatostatinomas are usually single, large, and accompanied with metastases at the time of diagnosis (18).
    In summary, we have presented herein a 46-yearold female case with a large functional somatostatinoma in the body and tail of the pancreas that resembled a diffuse infiltration tumor without metastases. Although the incidence of functional somatostatinoma is low and the diagnosis can only be confirmed by pathological examination, it should be considered in the list of the possible differential diagnoses of a large, hypervascularized tumor that resembles a diffuse infiltration tumor without distinct necrosis in the pancreas.
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  • Summary
  • Introduction
  • Case Presentation
  • Discussion
  • References
    • References
    1. Nesi G, Marcucci T, Rubio CA, et al. Somatostatinoma: clinico- pathological features of three cases and literature reviewed. J Gastroenterol Hepatol 2007; [Epub ahead of print].
    2. Harris GJ, Tio F, Cruz AB Jr. Somatostatinoma: a case report and review of the literature. J Surg Oncol 1987; 36: 8–16.
    3. Tjon A Tham RT, Jansen JB, Falke TH, et al. Imaging features of somatostatinoma: MR, CT, US, and angiography. J Comput Assist Tomogr 1994; 18: 427-31.
    4. Buetow PC, Miller DL, Parrino TV, Buck JL. Islet cell tumors of the pancreas: clinical, radiologic, and pathologic correlation in diagnosis and localization. Radiographics 1997; 17: 453-72.
    5. Larsson LI, Hirsch MA, Holst JJ, et al. Pancreatic somatostatinoma. Clinical features and physiological implications. Lancet 1977; 26: 666-8.
    6. Soga J, Yakuwa Y. Somatostatinoma/inhibitory syndrome: a statistical evaluation of 173 reported cases as compared to other pancreatic endocrinomas. J Exp Clin Cancer Res 1999; 18: 13-22.
    7. Debas HT, Mulvihill SJ. Neuroendocrine gut neoplasms. Important lessons from uncommon tumors. Arch Surg 1994; 129: 965-71.
    8. Ganda OP, Weir GC, Soeldner JS, et al. “Somatostatinoma”: a somatostatin-containing tumor of the endocrine pancreas. N Engl J Med 1977; 296: 963-7.
    9. Kaneko H, Yanaihara N, Ito S, et al. Somatostatinoma of the duodenum. Cancer 1979; 44: 2273-9.
    10. Tomassetti P, Migliori M, Lalli S, et al. Epidemiology, clinical features and diagnosis of gastroenteropancreatic endocrine tumours. Ann Oncol 2001; 12 (Suppl): S95-9.
    11. Usui M, Matsuda S, Suzuki H, et al. Somatostatinoma of the papilla of Vater with multiple gastrointestinal stromal tumors in a patient with von Recklinghausen's disease. J Gastroenterol 2002; 37: 947-53.
    12. Jensen RT, Norton JA. Endocrine tumors of the pancreas. In: Sleisinger MH, Fordtran JS, eds. Gastrointestinal disease: pathophysiology/diagnosis/management. Philadelphia, PA: W.B. Saunders Co, 1993; 1695-721.
    13. Soga J, Yakuwa Y. Somatostatinoma/inhibitory syndrome: a statistical evaluation of 173 reported cases as compared to other pancreatic endocrinomas. J Exp Clin Cancer Res 1999; 18: 13-22.
    14. Mao C, Shah A, Hanson DJ, et al. Von Recklinghausen's disease associated with duodenal somatostatinoma: contrast of duodenal versus pancreatic somatostatinomas. J Surg Oncol 1995; 59: 67-73.
    15. Tanaka S, Yamasaki S, Matsushita H, et al. Duodenal somatostatinoma: a case report and review of 31 cases with special reference to the relationship between tumor size and metastasis. Pathol Int 2000; 50: 146-52.
    16. Rockall AG, Reznek RH. Imaging of neuroendocrine tumors (CT/MR/US). Best Pract Res Clin Endocrinol Metab 2007; 21: 43-68.
    17. Sheth S, Hruban RK, Fishman EK. Helical CT of islet cell tumors of the pancreas: typical and atypical manifestations. Am J Roentgenol 2002; 179: 725-30.
    18. Pereira PL, Wiskirchen J. Morphological and functional investigations of neuroendocrine tumors of the pancreas. Eur Radiol 2003; 13: 2133-46.
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  • Summary
  • Introduction
  • Case Presentation
  • Discussion
  • References
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