Radiological Category Gastrointestinal Principal Modality 1 CT Principal

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Radiological Category: Gastrointestinal Principal Modality (1): CT Principal Modality (2): NM Case Report #

Radiological Category: Gastrointestinal Principal Modality (1): CT Principal Modality (2): NM Case Report # 766 Submitted by: Heng-Hsiao Liu, M. D. Faculty reviewer: Eduardo Matta, M. D. and David Wan, M. D. , The University of Texas Medical School at Houston Date accepted: 15 February, 2011

Case History 65 year old female with hypertension, hyperlipidema, and morbid obesity s/p lap

Case History 65 year old female with hypertension, hyperlipidema, and morbid obesity s/p lap banding a few years ago presents with 6 months of episodic, symptomatic hypoglycema, worse in the past two months.

Radiological Presentations Clockwise from top right: Axial CT images in the unenhanced, arterial, and

Radiological Presentations Clockwise from top right: Axial CT images in the unenhanced, arterial, and portal venous phases

Radiological Presentations Coronal and sagittal enhanced CT images in the arterial phase

Radiological Presentations Coronal and sagittal enhanced CT images in the arterial phase

Radiological Presentations Axial enhanced CT images in the arterial phase

Radiological Presentations Axial enhanced CT images in the arterial phase

Test Your Diagnosis Which one of the following is your choice for the appropriate

Test Your Diagnosis Which one of the following is your choice for the appropriate diagnosis? After your selection, go to next page. • Pancreatic adenocarcinoma • Solid pseudopapillary tumor of the pancreas • Islet cell tumor • Accessory spleen • Metastatic disease

Follow-Up Question Which nuclear medicine study can help better characterize the lesion? After your

Follow-Up Question Which nuclear medicine study can help better characterize the lesion? After your selection, go to next page. • Sulfur colloid scan • Octreotide scan • MIBG scan • Heat damaged RBC scan

Radiological Presentations 4 hour whole body anterior (right) and posterior (left) planar images of

Radiological Presentations 4 hour whole body anterior (right) and posterior (left) planar images of an octreotide scan

Radiological Presentations 4 hour coronal SPECT images through the abdomen (going anterior to posterior)

Radiological Presentations 4 hour coronal SPECT images through the abdomen (going anterior to posterior)

Follow-Up Answer • Sulfur colloid scan • While this study may have helped in

Follow-Up Answer • Sulfur colloid scan • While this study may have helped in excluding an accessory spleen, an insulinoma should be suspected based on the clinical history. • Octreotide scan • Correct answer. An insulinoma was suspected based on clinical history, and focal uptake would support the diagnosis. The exam can also assess for multifocal or metastatic disease. • MIBG scan • While this study may have helped in excluding a pheochromocytoma (as adrenal masses may sometimes mimic a pancreatic mass), this is not suggested by the clinical history, and the adrenal glands are clearly separate from the pancreatic mass on CT. • Heat damaged RBC scan • Another option to look for an accessory spleen, which was not suspected on clinical exam.

Findings and Differentials Findings: CT images reveal a well-circumscribed, slightly lobulated, homogenously hypervascular mass

Findings and Differentials Findings: CT images reveal a well-circumscribed, slightly lobulated, homogenously hypervascular mass in the pancreatic tail which demonstrates subtly greater attenuation to the spleen on the arterial phase. No vascular involvement or lymphadenopathy is present. No liver masses are seen. A lap band is seen in appropriate position. Whole body and coronal SPECT images through the abdomen of an octreotide scan reveal focal radiotracer uptake near the splenic hilum between the stomach and spleen which corresponds to the hypervascular lesion in the pancreatic tail on CT, consistent with a somatostatin receptor positive tumor. No other focal abnormal uptake is seen in the body to suggest multifocal or metastatic disease. Differentials: • Accessory spleen • Metastatic disease • Solid pseudopapillary tumor of the pancreas • Pancreatic adenocarcinoma

Findings Axial CT images in the unenhanced, arterial, and portal venous phases show a

Findings Axial CT images in the unenhanced, arterial, and portal venous phases show a well-defined, slightly lobulated hypervascular mass in the pancreatic tail.

Findings Coronal and sagittal enhanced CT images in the arterial phase confirm that the

Findings Coronal and sagittal enhanced CT images in the arterial phase confirm that the mass is clearly within the pancreatic tail.

Findings Axial enhanced CT images in the arterial phase again show the well-defined, hypervascular

Findings Axial enhanced CT images in the arterial phase again show the well-defined, hypervascular mass in the pancreatic tail. No lymphadenopathy or liver masses. No vascular involvement.

Findings Whole body planar images show focal uptake at the splenic hilum. No evidence

Findings Whole body planar images show focal uptake at the splenic hilum. No evidence of multifocal or metastatic disease.

Findings SPECT images show that the focal uptake is anterior and medial to the

Findings SPECT images show that the focal uptake is anterior and medial to the spleen, correlating with the hypervascular mass seen on CT scan.

Discussion Islet cell tumors can be associated with MEN 1 and are subdivided into

Discussion Islet cell tumors can be associated with MEN 1 and are subdivided into hyperfunctioning and nonhyperfunctioning categories, with the former including insulinoma, gastrinoma, somatostatinoma, VIPoma, and ACTH-producing tumors causing Cushing’s syndrome. Insulinomas are the most common islet cell tumors, followed by gastrinomas, with nonhyperfunctioning tumors taking up the rear. 90% of insulinomas are benign, in contrast to gastrinomas, 60% of which are multiple and malignant, and nonhyperfunctioning tumors, 80 -100% of which are malignant. Patients present with Whipple’s triad of fasting hypoglycemia, hypoglycemic symptoms, and immediate improvement following glucose administration. Of the functioning islet cell tumors, insulinomas are generally the smallest, averaging about 2 cm and present as solid, homogenous masses. Gastrinomas are roughly twice as large and are also usually solid, homogenous masses. Cystic changes and necrosis are more characteristic of the remainder of the islet cell tumors, which tend to be even larger and are more likely to demonstrate calcification, local invasion, vascular invasion, and metastatic disease. Although uptake on an octreotide scan is nonspecific, it may be helpful in detecting sites of ectopic, multifocal, or metastatic disease. Insulinomas are ectopic in 15% of cases and may be found in the duodenum, stomach, lymph nodes, or ovary.

Discussion Optimal therapy for insulinomas is curative surgical resection. In the past, 10 -20%

Discussion Optimal therapy for insulinomas is curative surgical resection. In the past, 10 -20% of lesions could not be identified during surgical exploration. In recent years, the combined techniques of intraoperative sonography and palpation have increased sensitivites to near 100%, but both techniques require experience to perform and interpret. Additionally, these techniques prolong surgery and increase the likelihood of rupture of the splenic vessels from pancreatic mobilization. Therefore, preoperative localization is paramount. Based on the most recent research, dual phase thin-collimation multidetector CT and MR imaging show high sensitivities (85 -100%) with relatively low risk. Somatostatin receptor scintography is limited by the fact that not all neuroendocrine tumors express enough somatostatin receptors to be detected. Only 60 -70% of insulinomas express somatostatin receptors. In cases where the octreotide scan is negative, FDG PET may be helpful to localize the tumor, as well as identify sites of ectopic, multifocal, or metastatic disease, although focal regions of uptake are less specific on PET when compared to uptake on an octreotide scan.

Pathology H&E stain of a resected pancreatic tail mass at low power reveals sheets

Pathology H&E stain of a resected pancreatic tail mass at low power reveals sheets of small, uniform, blue cells which are separated into lobules by intervening fibrovascular septae. Photos courtesy of Dr. Ekene Uzoigwe of UTH Pathology

Pathology H&E stain of a resected pancreatic tail mass at medium power reveals a

Pathology H&E stain of a resected pancreatic tail mass at medium power reveals a fibrous capsule (arrow) surrounding the tumor. Photos courtesy of Dr. Ekene Uzoigwe of UTH Pathology

Pathology H&E stain of a resected pancreatic tail mass at high power better defines

Pathology H&E stain of a resected pancreatic tail mass at high power better defines sheets of small, uniform, blue cells. Photos courtesy of Dr. Ekene Uzoigwe of UTH Pathology

Pathology H&E stain of a resected pancreatic tail mass at high power reveals a

Pathology H&E stain of a resected pancreatic tail mass at high power reveals a welldifferentiated neoplasm with less than 2 mitoses per high power field. Photos courtesy of Dr. Ekene Uzoigwe of UTH Pathology

Pathology For comparison, an H&E stain of a normal pancreas at high power reveals

Pathology For comparison, an H&E stain of a normal pancreas at high power reveals normal islet cells (pink) in a background of acinar cells (purple), the latter of which contains abundant cytoplasmic eosinophilic granules. Photos courtesy of Dr. Ekene Uzoigwe of UTH Pathology

Differential Diagnosis Pancreatic adenocarcinoma classically presents as an irregular, hypovascular, locally invasive mass with

Differential Diagnosis Pancreatic adenocarcinoma classically presents as an irregular, hypovascular, locally invasive mass with abrupt termination of the pancreatic and/or the common bile duct. However, they may be isoattenuating lesions early in the disease, causing only mild pancreatic ductal dilatation. The patient is older than would be expected for solid pseudopapillary tumor of the pancreas (SPPT) which is typically seen in adolescent and young women. On imaging, SPPT tend to be large (ranging from 6 -10 cm) with internal cystic and necrotic changes. A fibrous capsule and internal hemorrhage, when present, can be distinguishing features. However, they can be solid and homogenous when they are small. An accessory spleen is possible given its proximity to the spleen and its attenuation similar to the spleen on all phases. The tail of the pancreas is the second most common site for an accessory spleen, with the most common site being the splenic hilum. However, it should not accumulate radiotracer on the octreotide scan. Metastatic disease is always a possibility, with renal cell carcinoma being of particular interest as it is the most common and can present as a hypervascular pancreatic mass years after nephrectomy. Other hypervascular metastases include thyroid cancer and melanoma.

Differential Diagnosis Figures 1 a and 1 b. Isoattenuating pancreatic adenocarcinoma. Axial enhanced CT

Differential Diagnosis Figures 1 a and 1 b. Isoattenuating pancreatic adenocarcinoma. Axial enhanced CT images reveal an subtle, isoattenuating lesion within pancreatic neck with upstream dilatation of the pancreatic duct. Kim J H et al. Radiology 2010; 257: 87 -96. © RSNA

Differential Diagnosis Figures 2 a and 2 b. Solid pseudopapillary tumor of the pancreas.

Differential Diagnosis Figures 2 a and 2 b. Solid pseudopapillary tumor of the pancreas. Axial enhanced CT image in the portal venous phase (left) reveals a focal region of hypoattenuation within the pancreatic head (black arrow. ) Axial enhanced CT image in the pancreatic phase (right) in another patient reveals a homogenous, hypoattenuating lesion within the pancreatic tail (white arrow). Coleman K M et al. Radiographics 2003; 23: 1644 -1648. (left) © RSNA Baek J H et al. Radiology 2010; 257: 97 -106. (right) © RSNA

Differential Diagnosis Figure 3. Intrapancreatic accessory spleen. Axial enhanced MR image (left) in another

Differential Diagnosis Figure 3. Intrapancreatic accessory spleen. Axial enhanced MR image (left) in another patient shows a lesion (*) in the pancreatic tail (P) that is isointense to the spleen (S). To’o K J et al. Radiographics 2005; 25: 949 -965. © RSNA

Differential Diagnosis Figure 4. Renal cell metastasis. Axial enhanced CT image in the arterial

Differential Diagnosis Figure 4. Renal cell metastasis. Axial enhanced CT image in the arterial phase reveals a hypervascular (arrow) mass in the pancreatic head. Also note the solid mass in the left kidney (*). To’o K J et al. Radiographics 2005; 25: 949 -965. © RSNA

Diagnosis Insulinoma of the pancreatic tail

Diagnosis Insulinoma of the pancreatic tail

References Gouya H, Vignaux O, Augui J, Dousset B, Palazzo L, Louvel A, Chaussade

References Gouya H, Vignaux O, Augui J, Dousset B, Palazzo L, Louvel A, Chaussade S, Legmann P. CT, endoscopic sonography, and a combined protocol for preoperative evaluation of pancreatic insulinomas. AJR Am J Roentgenol. 2003 Oct; 181(4): 987 -92. Chung EM, Travis MD, Conran RM. Pancreatic tumors in children: radiologic-pathologic correlation. Radiographics. 2006 Jul-Aug; 26(4): 1211 -38. Kim JH, Park SH, Yu ES, Kim MH, Kim J, Byun JH, Lee SS, Hwang HJ, Hwang JY, Lee SS, Lee MG. Visually isoattenuating pancreatic adenocarcinoma at dynamic-enhanced CT: frequency, clinical and pathologic characteristics, and diagnosis at imaging examinations. Radiology. 2010 Oct; 257(1): 87 -96. Epub 2010 Aug 9. Figures 1 a and 1 b were reproduced with permission from Dr. Park and RSNA. Coleman KM, Doherty MC, Bigler SA. Solid-pseudopapillary tumor of the pancreas. Radiographics. 2003 Nov. Dec; 23(6): 1644 -8. Figure 2 a was reproduced with permission from Dr. Coleman and RSNA. Baek JH, Lee JM, Kim SH, Kim SJ, Kim SH, Lee JY, Han JK, Choi BI. Small (<or=3 cm) solid pseudopapillary tumors of the pancreas at multiphasic multidetector CT. Radiology. 2010 Oct; 257(1): 97 -106. Epub 2010 Jul 27. Figure 2 b was reproduced with permission from Dr. Lee and RSNA. To'o KJ, Raman SS, Yu NC, Kim YJ, Crawford T, Kadell BM, Lu DS. Pancreatic and peripancreatic diseases mimicking primary pancreatic neoplasia. Radiographics. 2005 Jul-Aug; 25(4): 949 -65. Figures 3 and 4 were reproduced with permission from Dr. Raman and RSNA.