Large Epidermoid Splenic Epithelial Cyst in a Young Female Presenting with Abdominal Pain: A Rare Occurrence

Summary: Primary splenic cysts are very rare in routine surgical practice representing only 10% of benign non-parasitic splenic cysts. Splenic cysts are usually an incidental finding during imaging studies performed for an unrelated reason and occur predominantly in pediatric to young adult age groups with a female predominance. We describe an unusual case of an 18-year-old woman who presented with left-sided shoulder pain with radiation to left upper quadrant and back. No history of previous trauma or foreign travel. CT imaging showed a large, multiseptated cystic lesion in the upper pole of the spleen. Splenectomy was performed revealing a 6.8 cm multiloculated cyst (Figure A). Microscopically, the cysts were lined by benign stratified squamous epithelium (Figure B) positive for CK 5/6 (Figure C) and focal mucous cells positive for mucicarmine (Figure D) characteristic of a primary epidermoid splenic epithelial cyst. The pathogenesis of primary splenic cysts remains unclear; hypotheses include a teratomatous origin, derivation from inclusion of fetal squamous epithelium, and origin from mesothelial invagination of the capsule during development, followed by squamous and mucinous metaplasia. A definitive pre-operative diagnosis is not possible; however the absence of previous trauma, infection or exposure to hydatid disease favor this diagnosis. Surgery is performed for diagnostic purposes and to avoid serious complications such as rupture or infection; conservative surgery is preferred when possible to maintain splenic function and avoid infectious complications related to asplenia.