Epithelial inclusion cyst arising within an intra-pancreatic splenunculus

Abstract

INTRODUCTION

An accessory spleen (splenunculus) may occur in up to 10% of the general population. However, an epithelial inclusion cyst originating within an intra-pancreatic splenunculus is an extremely rare finding, with only twenty-two previous cases described in medical literature.

PRESENTATION OF CASE

A 51-year-old male presented to our institution for investigation of altered bowel habit. Endoscopic ultrasound examination and CT scanning demonstrated an 18 mm cystic, well-demarcated lesion in the tail of the pancreas, resembling malignancy. Following laparoscopic spleen-preserving distal pancreatectomy, histological analysis confirmed epithelial inclusion cyst arising within an intra-pancreatic splenunculus.

DISCUSSION

The pre-operative radiological identification of such cystic pancreatic lesions is challenging. Surgical resection is usually performed for clinical suspicion of pancreatic malignancy.

CONCLUSION

Epithelial inclusion cyst originating within an intra-pancreatic accessory spleen is an extremely rare finding, which can mimic malignancy. Nevertheless, it should be carefully considered in the differential diagnosis of cystic lesions of the tail of the pancreas.

1. Introduction

Accessory spleens are relatively common, occurring in up to 10% of the general population. A fifth of these arise within the pancreatic tail, where they may be misinterpreted as cystic neoplasms on pre-operative imaging studies.¹ The discovery of an epithelial inclusion cyst originating within an intra-pancreatic accessory spleen (splenunculus) is exceedingly rare, with only twenty-two cases documented in medical literature since the original report by Davidson and colleagues in 1980.² Here we describe a case of an epithelial inclusion cyst arising within an intra-pancreatic spleen in an asymptomatic 51-year-old male, treated by laparoscopic distal pancreatectomy.

2. Presentation of case

A 51-year-old male initially presented to our institution for investigation of altered bowel habit. His past medical history included anxiety and varicose vein stripping twenty years previously. There was no hepatobiliary or pancreatic disease, or family history of note. Physical examination was unremarkable and laboratory blood parameters, along with tumour markers, were within normal limits.

Colonoscopy revealed evidence of diverticulitis. Gastroscopy confirmed moderately severe Helicobacter pylori-associated gastritis, for which eradication therapy with omeprazole, amoxicillin and clarithromycin was commenced. Endoscopic ultrasound examination showed an 18 mm cystic, well-demarcated, expansile lesion within the tail of the pancreas, very close to the splenic vein at the hilum of the spleen, containing a 9 mm-long papillary projection. Fine needle aspiration yielded yellowish fluid, with a normal carcino-embyonic antigen (CEA) level. CT scanning (Fig. 1, arrow) demonstrated a 2.3 cm × 1.8 cm well-defined low attenuation lesion arising exophytically from the tail of the pancreas; the pancreas itself appeared normal, with no focal calcification or pancreatic duct dilatation.

Fig. 1.

Axial CT scan demonstrating intra-pancreatic accessory spleen containing an epithelial inclusion cyst (arrow).

Since endoscopic ultrasound had demonstrated a 9 mm-long papillary projection in the wall of the cyst, thus complicating diagnosis, and considering the not insignificant size of the cyst, the case was discussed at a multi-disciplinary team meeting regarding management. In view of the unclear diagnosis, the options of surgical treatment to resect a potential pancreatic malignancy, versus careful observation with radiological follow-up, were thoroughly discussed with the patient. He decided to proceed with surgical resection.

Spleen-preserving distal pancreatectomy was proposed. At laparoscopy, there was no evidence of disease spread. Careful mobilisation of the transverse splenic flexure and descending colon enabled exposure of the splenic hilum. The pancreas appeared healthy; a small 2 cm cystic tumour was observed at the inferior border of the tail of the pancreas, in close proximity to the splenic vessels. The cystic lesion was then completely excised via distal pancreatectomy and specimens sent for histopathological examination. Macroscopically, the 2 cm cystic lesion was comprised of a thin wall encasing yellow necrotic material. Microscopic analysis revealed an epithelial cyst surrounded by a fibrous capsule (Fig. 2). The epithelial cyst was lined partly by non-keratinising stratified squamous epithelium (Fig. 3a) and partly by mesothelial-like epithelial cells (Fig. 3b), appearances compatible with an epithelial inclusion cyst. No malignant features were visualised. The final histopathological diagnosis was of an epithelial inclusion cyst arising from an intra-pancreatic accessory spleen (splenunculus). Post-operatively, the patient made a good recovery and was discharged home three days later. He is currently well on routine follow-up.

Fig. 2.

Microscopic examination (H&E, 40×) showing normal pancreas (P), accessory spleen (S), fibrous capsule (F), epithelial inclusion cyst (E), and cyst lumen (L).

Fig. 3.

(a) (H&E, 200×) Microscopic examination of epithelial inclusion cyst showing non-keratinising stratified squamous epithelium (arrow) lining the cyst. (b) (H&E, 100×) Microscopic examination of epithelial inclusion cyst showing mesothelial-like epithelial cells (arrow) lining the cyst.

3. Discussion

An accessory spleen is congenitally duplicated splenic tissue in a heterotopic location, found in up to 10% of the general population.³ Whilst 80% of accessory spleens occur at the splenic hilum, they may theoretically arise anywhere within the peritoneal cavity between the diaphragm and the pelvis.^3,4 Frequently, they are noted within the gastrosplenic or splenorenal ligaments, or mesentery. Intra-pancreatic accessory spleens are uncommon; those associated with a cystic lesion are even rarer.

Splenic cysts may be classified as type I (true) or type II (pseudocysts) depending on the presence or absence of an epithelial lining.⁵ In the aforementioned case, the cyst was lined by partly non-keratinising stratified squamous epithelium and partly mesothelial-like epithelial cells. Epidermoid cysts are lined by squamous epithelium and lack skin appendages, such as sebaceous and sweat glands.^3,4 They are relatively rare within the spleen, comprising only 10% of all non-parasitic splenic cysts.⁶ Epidermoid cyst in an intra-pancreatic accessory spleen is a very rare clinical entity, having only been reported twenty-two times since the original report by Davidson and colleagues in 1980.⁷

The pre-operative radiological identification of such cysts is challenging, and compounded by the wide differential diagnosis that entails pancreatic pseudocyst, serous cystic tumour, serous cystic adenoma, mucinous cystic tumour and intraductal papillary mucinous tumour. As a result, surgical resection is usually proposed for cystic lesions within the tail of the pancreas that are suspected malignant. In our patient, the finding of an abnormal papillary projection within the cyst wall and the moderate size of the cyst contributed to diagnostic uncertainty. Surgical resection was performed despite the relatively asymptomatic nature of the patient's presentation, due to the risk of overlooking a malignant pancreatic lesion.

4. Conclusion

We present a case of epidermoid cyst arising within an intra-pancreatic accessory spleen. Whilst this is a very rare finding, it should be carefully considered within the differential diagnosis of cystic lesions of the tail of the pancreas.

Conflict of interest statement

None.

Funding

None.

Ethical approval

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Author contributions

NP, MA, RA, DP, and LR assisted in manuscript preparation. RA provided histology slides. NP obtained radiological images.