Epidermoid Cyst arising within an Intrapancreatic Accessory Spleen [ECIPAS] mimicking a pancreatic mucinous cystic neoplasm-a case report with literature review

Background: Accessory spleens are congenital embryological aberrations usually found within the splenic hilum with no clinical significance. An Intra Pancreatic Accessory Spleen (IPAS) is an uncommon benign pancreatic lesion encountered clinically. The occurrence of an Epidermoid Cyst arising within an IPAS (ECIPAS) is exceedingly rare and is often misdiagnosed as a pancreatic pathology such as mucinous cystic neoplasm, cystic degeneration within a solid tumor such as a neuroendocrine tumor, or a lymph node. Case report: A 68-year-old male presented with intermittent post-prandial abdominal pain for over 2 years. Abdominal computer tomography identified a 5.2 cm calcified cyst within the pancreatic tail and a mucinous pancreatic neoplasm/pancreatic pseudocyst was considered in the differential diagnosis. The results of endoscopic ultrasound and fine needle aspiration were indeterminate. Due to persistent abdominal pain, the patient underwent a laparoscopic distal pancreatectomy with splenectomy. A gross examination of the distal pancreatic/splenectomy specimen confirmed a well-demarcated cystic lesion with brownish fluid within the pancreatic tail. Microscopic examination revealed a nonpathological pancreas separated by a fibrous capsule with a large cyst arising within an intrapancreatic accessory spleen. The cyst was lined with multilayered non-keratinized stratified squamous epithelium positive for pancytokeratin, CA 19-9, CK5/6, and p63 with no lymphocytic infiltrates and absent hair/ dermal appendages confirming an epidermoid cyst. CD8 outlined the dendritic network of the littoral cells of the splenic tissue in the cyst wall. Post-operative follow-up at 6 weeks was uneventful. Conclusion: The preoperative diagnosis of ECIPAS is extremely difficult as this entity shares overlapping radiological features with other cystic lesions such as mucinous pancreatic cysts. It is important for anatomic pathologists to recognize and consider the intrapancreatic compartment as a possible site for accessory spleen. As histopathology is the final determinant of this diagnosis, increased clinical awareness with an accurate diagnosis of this entity may prevent patients from unnecessary surveillance and/or extensive oncological-based surgical resection.