Epidermoid Cyst in an Intrapancreatic Accessory Spleen: Three Case Reports and Review of the Literatures

The development of an epidermoid cyst in an intrapancreatic accessory spleen is an extremely rare lesion, with only 17 cases being reported in the English literature. All such cases were located in the pancreatic tail, some of which showed carbohydrate antigen 19-9 (CA19-9) immunoreactivity in the lining of the epithelium. A few of them indicated an elevation of the serum CA19-9 level. Here we report three cases of an epidermoid cyst in an intrapancreatic accessory spleen. Cases 1 and 2 were 57-year-old and 70-year-old women, while case 3 was a 37-year-old man. All three cases were asymptomatic. Serum CA19-9 levels showed within normal limits (case 1), slightly elevated (case 2), and clearly elevated (case 3). They underwent a distal pancreatectomy with splenectomy (cases 1 and 2) and without splenectomy (case 3). Grossly, the surgical specimen was a well-demarcated, multiple (case 1) or solitary (cases 2 and 3) cystic mass in the pancreatic tail. A high level of fluid CA 19-9 was detected in case 1. Microscopically, the cystic walls were lined with squamous and cuboidal epithelium, which were surrounded by normal splenic tissue and hyalinized fibrous tissue. The lining squamous epithelium was revealed as nonkeratinizing (Cases 1and 2) or keratinizing (Case 3). Immunohistochemically, CA19-9 was positive in the monolayer and surface layer of the cuboidal epithelium, but negative for the keratinizing squamous epithelium. As for the histogenesis, it is suggested that the cystic lining of the epithelium may derive from the pancreatic duct which protrudes into the accessory spleen.