Approximately 16% of accessory spleens occur in or around the tail of the pancreas (1
). An epidermoid cyst in an IPAS is extremely rare and was first described in 1980 by Davidson et al
). Following this, 30 cases of epidermoid cyst of IPAS have been described in the literature. summarizes the 31 cases of epidermoid cyst in an IPAS, including the case we describe here. The cases involved 15 males and 16 females, with ages ranging from 12–70 years (mean, 46 years). All cysts were located in the pancreatic tail. While 16 patients were asymptomatic, various symptoms were observed in 14 patients, including weight loss, nausea, vomiting, abdominal pain and discomfort, back pain, epigastric pain and fever. Histological analysis revealed that the cysts were solitary or multilocular, lined with keratinized or non-keratinized stratified squamous epithelium or cuboidal epithelium, and in some cases exhibiting mixed-form epithelium.
Summary of the 31 cases of epidermoid cyst arising in intrapancreatic accessory spleen (IPAS), including the present case.
An elevation of serum CA 19-9 level was observed in 10 cases, hence the difficulty in pre-operatively differentiating between an epidermoid cyst in an IPAS and pancreatic malignancy during clinical analysis. Higaki et al
) revealed that the serum CA 19-9 level markedly decreased to within the normal range following surgery in a patient diagnosed with an epidermoid cyst in an IPAS, suggesting that the serum CA 19-9 originated in the epidermoid cyst in an IPAS.
The histogenesis of an epidermoid cyst in an IPAS may be identical to that of a splenic epidermoid cyst (23
). There are three hypotheses concerning the histogenesis of an epidermoid cyst in an IPAS (10
). Firstly, the cyst may originate from mesothelial inclusion with subsequent squamous metaplasa (30
). Secondly, teratomatous derivation or an inclusion of fetal squamous epithelium may cause cystic change (31
). Thirdly, a derivation from the pancreatic duct may protrude into the accessory spleen (10
). In a case described by Kadota et al
), there were pancreatic ducts in the fibrous tissue surrounding the accessory spleen tissue, and the squamous and cuboidal epithelia indicated a transitional appearance from one form to the other. Additionally, immunohistochemical analysis demonstrated that the staining results of the cystic epithelial lining were identical to those of the pancreatic duct. These results support the third hypothesis.
A pre-operative imaging diagnosis of an epidermoid cyst in an IPAS is extremely difficult. Notably, a diagnosis of abdominal CT in the present case was also pancreatic tail cancer. As there are no characteristic features to define the lesion on radiology, it is not possible to entirely differentiate the cystic pancreatic malignancy prior to surgery and histopathological examination (28
In conclusion, an epidermoid cyst in an IPAS is an extremely rare disease entity, and radiographic and clinical results (including CA 19-9 elevation) are similar to those of other cystic pancreatic neoplasms. As a result, the possibilty of such a cystic lesion should be considered in the differential diagnosis of a pancreatic cystic lesion.