Pitfalls in pancreatic lesion diagnostics: an accessory intrapancreatic spleen

Introduction. Accessory spleen (splenunculus) is one of the most common benign congenital anomalies in humans. The location of splenunculus may vary from perisplenic, greater omental or mesenterial to intraparenchymal (pancreas, stomach, duodenum, etc.). In the latter case, the additional spleen is called ectopic (from the greekektoposdisplaced). Most frequently detection of such splenic lobules occurs accidentally via abdominal ultrasound.

Objective: two cases of verified intrapancreatic accessory spleen (IPAS) and main criteria for differential diagnosis with other hypervascular pancreatic lesions.

Materials and methods. We present two case reports: a 43-year-old woman with a history of kidney cancer and a healthy 61-year-old man. In both cases, pancreatic neuroendocrine neoplasia (NEN) was initially suspected. Preoperative diagnostics included abdominal ultrasound examination and multiphase dynamic computed tomography (CT) with intravenous bolus nonionic iodine-based contrast agent (native, arterial – 10 sec, venous – 60 sec and delayed – 300 sec after threshold density of 150 HU in the aorta was exceeded). In one case magnetic resonance imaging (MRI) including axial, sagittal and coronal T1and T2-weighted images, diffusion-weighted images and dynamiccontrast-enhanced series with gadolinium chelate was performed. Both patients underwent robotic assisted distal pancreas resection. Morphological examination revealed IPAS.

Results. In contrast-enhanced computed tomography IPAS has densitometric parameters similar to the spleen. Generally, magnetic resonance imaging does not differentiate IPAS, NEN and hypervascular metastases, since all three are generally T2-hyperintense and T1-hypointense. Contrast enhancement pattern with gadolinium chelateswas similar to CT-contrast enhancement pattern.

Conclusion. Intrapancreatic accessory spleen does not require surgical treatment. Therefore, differential diagnosis between IPAS and neuroendocrine neoplasia, solid pseudopapillary tumor and hypervascular pancreatic metastases is crucial. MRI has an advantage with non-invasive diffusionweighted images (DWI). The apparent diffusion coefficient (ADC) of IPAS will be quantitatively similar to the main spleen while other lesion will demonstrate lower ADC values. Scintigraphy with red blood cells bound with 99mTc utilizes the reticuloendothelial system (RES) in the spleen demonstrating characteristic uptake in the IPASand the main spleen. Ultrasound with color Doppler and contrast enhancement may be a good addition to our armamentarium. One can evaluate the vascular pedicle of the IPAS, as well as contrast agent retention in RES via sonography. We believe the multimodal approach including MRI with DWI/ADC to be the most effective.

1. Movitz D. Accessory spleens and experimental splenosis. Principles of growth. The Chicago Medical School quarterly. 1967; 26; 183–187.

2. Beltrame V., Merigliano S., Sperti C. Splenosis. Presenting as Pancreatic Neoplasm: Report of Two Cases. Austin J. Gastroenterol. 2014; 1 (3): 1015.

3. Belik O.V., Katerenyuk I.M., Spinea L.V., Naku V.E. About accessory spleen. Clinical Anatomy and Operative Surgery. 2010; 9 (4); 31–35. (In Russian)

4. Wacha M. Laparascopic resection of an accessory spleen in a patient with chronic lower abdominal pain. Surg. Endosc. 2002; 16 (8): 1242–1243. DOI: 10.1007/s00464-001-4241-7

5. Halpert B., Gyorkey F. Lesions observed in accessory spleens of 311 patients. Am. J. Clin. Pathol. 1959; 32; 165–168.

6. Afanasiev Y.I., Yurina N.A., Kotovsky E.F. Histology, embryology, cytology: Textbook. 6th ed. Ch. 14. Moscow, 2012. 800 p. (In Russian)

7. Abdullin R.F., Kondratenko E.G., Koshik E.A., Ivanov D.V. Morphological characteristics of intrapancreatic accessory spleen in newborns and children of the first year of life. Sovremennaya pediatriya. 2014; 2 (58): 95–99. (In Russian)

8. Li B.Q., Xu X.Q., Guo J.C. Intrapancreatic accessory spleen: a diagnostic dilemma. HPB (Oxford). 2018. pii: S1365-182X(18)30807-4. DOI: 10.1016/j.hpb.2018.04.004.

9. Georgin-Lavialle S., Gossot D., Galicier L., Oksenhendler E., Fieschi C. Accessory spleens after splenectomy in a patient with common variable immunodeficiency. Rev. Mйd. Interne. 2010; 31 (1): 41–45. DOI: 10.1016/j.revmed.2009.06.006.

10. Herman T.E., Siegel M.J. CT of acute splenic torsion in children with wandering spleen. Am. J. Roentgenol. 1991; 156 (1): 151–153.

11. Danaci M., Belet Ь., Yalın T., Polat V., Nurol S., Selзuk M.B. Power Doppler sonographic diagnosis of torsion in a wandering spleen. J. Clin. Ultrasound. 2001; 60 (1): 246–248.

12. Kim S.H., Lee J.M., Han J.K., Lee J.Y., Kim K.W., Cho K.C., Choi B.I. Intrapancreatic Accessory Spleen: Findings on MR Imaging, CT, US and Scintigraphy, and the Pathologic Analysis. Korean J. Radiology. 2008; 9 (2): 162–174. DOI: 10.3348/kjr.2008.9.2.162.

13. Egorov A.V., Kuzin N.M. Diagnosis of neuroendocrine tumors of the pancreas. Practical oncology. 2005; 6 (4); 206–212. (In Russian)

14. Heitz P.U., Komminoth P., Perren A., Klimstra D.S., Dayal Y., Bordi C. Pancreatic endocrine tumors: introduction. In: De Lellis D.A., Lloyd R.V., Heitz P.U., Eng C. (eds). Pathology and genetics of tumours of endocrine organs. World Health Organization classification of tumours. Lyon, France: IARC Press, 2004: 177–182.

15. Noriyoshi Fukushima. Neuroendocrine Neoplasms of the Pancreas: The Pathological Viewpoint. J. Pancreas (Online). 2017; 28; S (3): 216–220.

16. Al-Hawarya M.M., Kazaa R.K., Azara S.F., Julie A., Francisa I.R.. Mimics of pancreatic ductal adenocarcinoma. Cancer Imaging. 2013; 13 (3): 342–349. DOI: 10.1102/1470-7330.2013.9012.

17. Subramanyam B.R., Balthazar E.J., Horii S.C. Sonography of the accessory spleen. Am. J. Roentgenol. 1984; 143; 47–49.

18. Kim S.H., Lee J.M., Lee J.Y., Han J.K., Choi B.I. Contrastenhanced sonography of intrapancreatic accessory spleen in six patients. Am. J. Roentgenol. 2007; 188: 422–428.

19. Herbay A., Vogt C., Hдussinger D. The ultrasound contrast agent levovist helps with the differentiation between accessory spleenand lymph nodes in the splenic hilum: a pilot study. Z. Gastroenterol. 2004; 42 (10): 1109–1115.

20. Belousova E., KarmazanovskyG., Kriger A., Kalinin D., Mannelli L., Glotov A., Karelskaya N., Paklina O., Kaldarov A. Contrast-enhanced MDCT in patients with pancreatic neuroendocrine tumours: correlation with histological findings and diagnostic performance in differentiation between tumour grades. Clin. Radiol. 2017; 72 (2): 150–158. DOI: 10.1016/j.crad.2016.10.021.

21. Osher E., Scapa E., Klausner J., Greenman Y., Tordjman K., Melhem A., Nachmany I., Sofer Y., Geva R., Blachar A., SternN., Santo E. Pancreatic incidentaloma: differentiating nonfunctioning pancreatic neuroendocrine tumors from intrapancreatic accessory spleen. Endocrine Practice. 2016; 22 (7): 773–779. DOI: 10.4158/EP151091.OR.

22. Coquia S.F., Kawamoto S., Zaheer A., Bleich K.B., Blackford A.L., Hruban R.H., Fishman E.K. Intrapancreatic accessory spleen: possibilities of computed tomography in differentiation from nonfunctioning pancreatic neuroendocrine tumor. J. Computer Assis. Tomogr. 2014; 38 (6): 874–878. DOI: 10.1097/RCT.0000000000000127.

23. Brahms H.-Y. Radiation diagnostics. Gastrointestinal tract; trans. from the English; under the Society. Ed. Prof. Valkova M.Yu. 2nd ed. M.: MEDpress-inform, 2014: 148– 156. (In Russian)

24. Kim S.H., Lee J.M., Han J.K., Lee J.Y., Kang W.J., Jang J.Y., Shin K.S., Cho K.C., Choi B.I. MDCT and superparamagnetic iron oxide (SPIO)-enhanced MR findings of intrapancreatic accessory spleen in seven patients. Eur. Radiol. 2006; 16 (9): 1887–1897. DOI: 10.1007/s00330-006-0193-6.

25. Kang B.K., Kim J.H., Byun J.H., Lee S.S., Kim H.J., Kim S.Y., Lee M.G. Diffusion-weighted MRI: usefulness for differentiating intrapancreatic accessory spleen and small hypervascular neuroendocrine tumor of the pancreas. Eur. Radiol. 2018; 28 (4): 1560–1567. DOI: 10.1007/s00330-017-5122-3.

26. Pandey A., Pandey P., Ghasabeh M.A., Varzaneh F.N., Khoshpouri P., Shao N., Pour M.Z., Fouladi D.F., Hruban R.H., O'Broin-Lennon A.M., Kamel I.R. Accuracy of apparent diffusion coefficient in differentiating pancreatic neuroendocrine tumour from intrapancreatic accessory spleen. Eur. Radiol. 2018; 28 (4): 1560–1567. DOI: 10.1007/s00330-017-5122-3.

27. Jang K.M., Kim S.H., Lee S.J., Park M.J., Lee M.H., Choi D. Differentiation of an intrapancreatic accessory spleen from a small (<3 cm) solidpancreatictumor: value of diffusion-weighted MR imaging. Radiology. 2013; 266 (1): 159–167. DOI: 10.1148/radiol.12112765.

28. Spencer L.A., Spizarny D.L., Williams T.R. Imaging features of intrapancreatic accessory spleen. Br. J. Radiol. 2010; 83 (992): 668–673. DOI: 10.1259/bjr/20308976.