(Radiology. 2000;217:134-137.)
© RSNA, 2000
Case 27: Intrapancreatic Accessory Spleen1
Gregory T. Sica, MD and
Michael F. Reed, MD
1 From the Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis St, Boston, MA 02115. Received January 18, 1999; revision requested March 3; final revision received June 28; accepted July 13. Address correspondence to G.T.S. (e-mail: gsica@partners.org).
Index terms: Diagnosis Please • Pancreas, CT, 770.12111 • Pancreas, MR, 770.121411, 770.121415 • Spleen, abnormalities, 775.134
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HISTORY
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A 40-year-old woman presented with a 16-month history of left upper quadrant pain and nausea. All biochemical laboratory study results were negative, and physical examination findings were unremarkable. Abdominal ultrasonography was performed and raised suspicion of a pancreatic mass (images not available). Abdominal computed tomography (CT) was performed without the use of intravenous contrast material for the evaluation of abdominal pain (Fig 1). Magnetic resonance (MR) imaging of the abdomen was performed subsequently (Figs 2–5).
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Figure 1. Transverse CT image of the abdomen obtained without intravenous contrast material. A focal bulge (arrow) in the contour of the tail of the pancreas is noted. The attenuation is similar to that of the adjacent spleen (arrowhead).
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Figure 2. Contiguous transverse T2-weighted fast spin-echo abdominal MR images (repetition time msec/echo time msec = 5,000/112 [effective], 256 x 192, two signals acquired). The mass (white arrows) is of intermediate to mildly hyperintense signal intensity, similar to that of the adjacent spleen (arrowheads) and greater than the low to intermediate signal intensity surrounding the pancreas (black arrows). L = left, R = right.
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Figure 3. Contiguous transverse T1-weighted breath-hold fast multiplanar spoiled gradient-echo abdominal MR images (150/4.4, 75° flip angle, 256 x 128, one signal acquired). The normal pancreatic parenchyma (black arrows) is of increased signal intensity. The mass (white arrow) in the tail of the pancreas is hypointense to the pancreatic parenchyma but isointense to the adjacent spleen (arrowhead). L = left, R = right.
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Figure 4. Contiguous transverse fat-saturated T1-weighted spin-echo abdominal MR images (600/14, 256 x 192, two signals acquired). Inhomogeneous fat saturation is present. The mass (solid arrow) is hypointense, similar to the adjacent spleen (arrowhead); the surrounding pancreas (open arrows) is hyperintense. L = left, R = right.
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Figure 5. Transverse fat-saturated T1-weighted fast multiplanar spoiled gradient-echo abdominal MR images (300/1.6, 75° flip angle, 256 x 128, one signal acquired) obtained during the arterial phase (left) and delayed phase (right) after the intravenous administration of a bolus of 20 mL of gadopentetate dimeglumine. On the arterial-phase image, early enhancement of the mass (arrow) is noted, similar to that of the spleen (arrowhead). On the delayed phase image, enhancement diminishes similarly in the mass (arrow) and spleen (arrowhead). R = right.
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IMAGING FINDINGS
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A nonenhanced CT scan (Fig 1) showed focal, masslike enlargement of the tail of the pancreas. This area was isoattenuating with both the spleen and the remainder of the pancreas. A well-defined 2.5-cm, solid, enhancing mass was identified on MR images, and, for all sequences, was of similar signal intensity as that of the adjacent spleen. The mass was of intermediate to mildly hyperintense T2-weighted fast spin-echo signal intensity, which was greater than that of the surrounding pancreas (Fig 2). The breath-hold T1-weighted fast spoiled gradient-echo sequence (Fig 3) and the T1-weighted fat-saturated spin-echo sequence (Fig 4) demonstrated a mass of low signal intensity that was surrounded by the higher signal intensity pancreas. Moderate homogeneous enhancement of the mass was present during the arterial phase of the dynamic fast multiplanar spoiled gradient-echo sequence, with diminished enhancement in the delayed phase (Fig 5). The enhancement was similar to that of the adjacent spleen.
Of note, the adjacent pancreatic tissue was normal in appearance on both the CT and MR images. No adenopathy or other pathologic process was noted in the abdomen. An additional 1.0-cm splenule anterior to the spleen was seen incidentally on the CT scan and was confirmed at surgery. A photograph of the pathologic specimen (Fig 6) obtained by means of distal pancreatectomy and splenectomy showed the intrapancreatic splenule, adjacent pancreas, and spleen.
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DISCUSSION
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Intrapancreatic accessory spleen has been documented and described in previous case reports (1–5). Accessory spleens are found in up to 30% of unselected autopsy cases and consist of structurally normal splenic tissue (1,6). They range in size from a few millimeters to several centimeters, may be single or multiple, and may enlarge after splenectomy (6,7). As their origin is congenital, they are restricted to sites within the embryologic dorsal mesentery of the stomach and pancreas (7,8). They are found most commonly near the splenic hilum (6), with almost 20% in or near the pancreatic tail (5,9). Halpert and Gyorkey (10) reported one in every six accessory spleens to be located in the pancreatic tail. In splenosis, which is usually a result of trauma with autotransplantation of splenic tissue, implantation of splenic tissue may occur anywhere in the abdomen, pelvis, or even chest (8). Symptoms are rare, but pain and nausea have been reported (1,5,8,11).
At CT and MR imaging, accessory spleens are suggested by their characteristic location and appearance similar to the spleen on nonenhanced and contrast material–enhanced images (1,2,5,7). The imaging findings in the case presented, therefore, make this the most likely diagnosis. Confirmation can be obtained by means of scintigraphy, which although providing inferior spatial resolution, is the most specific imaging study for diagnosing functioning ectopic splenic tissue (12). Technetium 99m sulfur colloid scans, although most commonly used, may not demonstrate uptake (8,13). Radiolabeled heat-damaged red blood cells and indium 111–labeled autologous platelets also have been used to image splenic tissue and may demonstrate lesions not depicted on 99mTc sulfur colloid scans (8,14,15). The patient’s symptoms resolved postoperatively, which suggests the cause may have been related to this lesion.
Recognition of the characteristic imaging findings by using multiple modalities would help obviate surgery, as in this case in which a malignancy was considered in the differential diagnosis and not excluded preoperatively by means of percutaneous biopsy. Findings on an individual study, however, may suggest several diagnoses for a solid enhancing mass. These include (a) solid and papillary epithelial neoplasm, (b) islet cell tumors, (c) pancreatic adenocarcinoma, and even (d) metastases.
Solid and papillary epithelial neoplasms, described by Hamoudi et al (16) in 1970, are an uncommon, low-grade malignancy that occurs predominantly in young female patients (17). Preoperative recognition is important, as the tumor usually is curable by means of resection (18). The tumor grossly is an encapsulated and sharply demarcated pancreatic mass, most commonly in the tail, and typically large, with a mean size of 9 cm in the study by Buetow et al (18). The internal architecture varies from predominantly solid, to solid and cystic, to a thick-walled cyst (17), although the mixed type is more common (18). The imaging appearance reflects gross disease.
Tumors typically contain areas of cystic degeneration and hemorrhage, which are well demonstrated by means of intravenous contrast-enhanced CT and MR examinations. MR imaging is particularly well suited to demonstrate the heterogeneity of T1 and T2 signal intensities associated with hemorrhage and cystic degeneration. Fluid-debris levels may be seen (18). Smaller lesions may demonstrate less heterogeneity, and nonenhanced CT or MR images may appear similar to those seen in the current case. The appearance of a solid, homogeneously enhancing mass, as is expected with an accessory spleen, would be unusual for a solid and papillary epithelial neoplasm.
Islet cell tumors of the pancreas occur in up to 1.6% of the population and appear to be evenly distributed throughout the gland (19). Approximately 95% are hormonally active, but up to one-third produce no hormone-related symptoms (ie, they are nonhyperfunctioning) (19). Patients with functioning tumors typically present with a characteristic syndrome and earlier than those with nonhyperfunctioning tumors. Insulinomas are most common and appear in 60%–75% of cases, followed by gastrinoma in 20% of cases (20). Insulinomas typically are homogeneous, hypervascular masses up to 2 cm in diameter. Gastrinomas are often less than 4 cm in diameter and moderately vascular (21).
Nonhyperfunctioning islet cell tumors are larger and have a propensity for cystic change and necrosis, which is reflected in their imaging appearance (22). Functioning tumors often demonstrate uniform or ringlike enhancement at either CT or MR imaging (19,21) and may be more conspicuous in the early arterial phase (19). The masses are typically hypointense to the pancreas on T1-weighted images and hyperintense on T2-weighted images, but isointense T2-weighted signal intensity also is reported (23). This patient’s presenting symptoms were nonspecific, but there were no biochemical abnormalities to suggest a hyperfunctioning islet cell tumor. There is overlap in the imaging appearance of an islet cell tumor and that of a solid and papillary epithelial neoplasm; however, given the more typical appearance of an islet cell tumor, diagnosis of islet cell tumor would not be most likely.
Pancreatic adenocarcinoma has a peak age of incidence in the 7th decade of life and rarely affects those younger than 40 years of age (19). Presenting symptoms and signs, aside from pain, include loss of appetite, weight loss, fatigue, nausea, vomiting, and jaundice. Approximately 5% are solely in the tail, and 60%–70% occur in the head of the pancreas (19). The masses may be iso- to hypoattenuating on nonenhanced CT scans and are hypovascular, after the intravenous administration of contrast material, as shown on CT and MR images (20,24). T1 signal intensity is usually iso- to hypointense. Although T2 signal intensity can range from hypo- to slightly hyperintense, adenocarcinomas tend to be of low conspicuity on T2-weighted images (25–27).
With multimodality studies, the appearance of an accessory spleen is sufficiently different from that of pancreatic adenocarcinoma so that a specific diagnosis of the latter can be made. Given the imaging studies performed in the current case, however, pancreatic adenocarcinoma would be included in the differential diagnosis but should be considered low on the list. The clinical presentation of pain is nonspecific, and pancreatic adenocarcinoma both in a 40-year-old patient and located in the pancreatic tail would be unusual.
Hematogenous metastases to the pancreas are uncommon and usually manifest in advanced disease. The incidence is highest in patients with melanoma, breast carcinoma, and bronchogenic carcinoma (19). The imaging findings are similar to those of pancreatic adenocarcinoma. Renal cell carcinoma metastases may demonstrate a hypervascular appearance (19).
Our congratulations to the 48 individuals who submitted the most likely diagnosis (intrapancreatic accessory spleen) for Diagnosis Please, Case 27. The names and locations of the individuals, as submitted, are as follows:
- Gholamali Afshang, MD, Tinley Park, Ill
- Yasutaka Baba, Kagoshima, Japan
- Edward L. Baker, MD, San Francisco, Calif
- Ken Baliga, Rockford, Ill
- Nelson M. G. Caserta, MD, Campinas, Brazil
- Bharath K. Chinta, Philadelphia, Pa
- Pablo Cikman, MD, Cordoba, Argentina
- Marc G. de Baets, MD, Lugano, Switzerland
- Kemal Demir, MD,
stanbul, Turkey
- Eduardo Eyheremendy, Buenos Aires, Argentina
- Sandra K. Fernbach, MD, Chicago, Ill
- Milton Fuentealba, MD, General Roca, Rio Negro, Argentina
- Akira Fujikawa, MD, Tokyo, Japan
- Teresa Adriana Garcia, MD, Capital Federal, Buenos Aires, Argentina
- Dietrich Gerhardt, Waterloo, Iowa
- Manoj Jain, Chandigarh, India
- Albert Kaminsky, Melbourne, Victoria, Australia
- Ryuji Katada, MD, Sapporo, Japan
- Eito Kozawa, Bryn Mawr, Pa
- Glenn Krinsky, New York, NY
- David Kurti, MD, Naperville, Ill
- Wen-jeng Lee, Taipei, Taiwan
- Yoji Maetani, Kyoto, Japan
- N. B. S. Mani, MD, Chandigarh, India
- Hidetoshi Miyake, MD, Oita, Japan
- Sergio J. Moguillansky, MD, Cipolletti, Rio Negro, Argentina
- Dr. Eduardo Mondello, Buenos Aires, Argentina
- Toshio Moritani, Rochester, NY
- Vamsi Narra, MD, St Louis, Mo
- Vung Nguyen, MD, San Antonio, Tex
- Mizuki Nishino, MD, Kyoto, Japan
- David M. Panicek, MD, New York, NY
- Gerardo Paz, MD, Cali, Colombia
- Dr. Roberto E. Perez Gautrin, Hermosillo, Sonora, Mexico
- Juan Pablo Perotti, Buenos Aires, Argentina
- Carlo L. E. Petralli, MD, Bruderholz, Switzerland
- John M. Plotke, Naperville, Ill
- R. Prashant, Ahmedabad, India
- Matt Shapiro, MD, Lowell, Mass
- Taro Shimono, MD, Kyoto, Japan
- Juan Carlos Spina, MD, Ciudad Evita, Argentina
- Dr. Juan Carlos Spina Ramos, Buenos Aires, Argentina
- J. Takasugi, Mercer Island, Wash
- Shendee Teng, MD, Woodbridge, NJ
- Carlos E. Triana
- Philippe Vanlede, MD, Izegem, Belgium
- Joe Yut, Olathe, Kan
- Marc Zins, MD, Paris, France
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FOOTNOTES
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Part 1 of this case appears 4 months previously and may contain larger images.
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TOP
HISTORY
IMAGING FINDINGS
