Pancreatic Endometriosis Coexisting with a Splenic Mesothelial Cyst: A Rare Case Report and Review of the Literature

Endometriosis is a clinical entity affecting up to 10% of women of reproductive age, characterized by ectopic endometrial tissue outside the uterine cavity. While extrapelvic endometriosis has been documented, pancreatic endometriosis remains extremely rare and poses significant diagnostic challenges due to its similarity to other pancreatic diseases. At the same time, splenic mesothelial cysts are also rare and typically benign. This report presents a unique case of pancreatic endometriosis coexisting with a splenic mesothelial cyst in a 31-year-old woman. The patient presented to the emergency department with complaints of persistent epigastric and low back pain. She noted having similar symptoms approximately a year prior. Her past medical history was otherwise unremarkable, and there was no known family history of pancreatic disease or neoplasms. Initial imaging revealed a 3.8 cm cystic lesion in the pancreatic tail, with features suggestive of mucinous cystadenoma. Following clinical evaluation and confirmation of the cyst's nature through endoscopic ultrasound-guided biopsy, the patient subsequently underwent laparoscopic distal pancreatectomy and splenectomy due to worsening symptoms. Gross examination revealed a multilocular pancreatic cyst with a smooth, hemorrhagic wall. Microscopic analysis showed the cyst to be lined by cuboidal to columnar epithelium, consistent with pancreatic endometriosis, confirmed by immunohistochemical staining. The spleen showed cystic formations, diagnosed as a multifaceted mesothelial cyst. In conclusion, this report is the first to document the coexistence of pancreatic endometriosis and splenic mesothelial cysts, highlighting the importance of accurate imaging and pathologic evaluation in the diagnosis of these rare conditions. Early diagnosis and surgical intervention lead to favorable outcomes, reinforcing the importance of comprehensive diagnostic strategies.