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Exploration of the abdomen revealed a huge cystic lesion that had originated from the spleen. The mass was not connected to the pancreas. Microscopic examination showed that the cyst was lined by stratified squamous epithelium, confirming a diagnosis of epidermoid cyst. After 1 year of follow-up, the patient was in good clinical condition.

Splenic cyst is a rare condition with a reported incidence of 0.07% in a review of 42 327 autopsies.¹Cystic lesions of the spleen comprise parasitic and nonparasitic cysts.²Parasitic cysts are due almost exclusively to echinococcal disease and account for 60% to 70% of all splenic cysts in countries where hydatid disease is endemic. Nonparasitic cysts are classified as primary or true cysts, whose lumen is lined by epithelial tissue, and pseudocysts. Pseudocysts are much more common and probably result from liquefaction of old hematomas or areas of infarction and inflammation. Primary cysts of the spleen are uncommon lesions and occur in younger individuals, usually younger than 40 years. Of the true splenic cysts, epidermoid cysts account for 90%, while dermoid cysts are less common and compose the remaining 10%.³

The differential diagnosis of a true cyst includes posttraumatic and parasitic cysts, teratomas, aneurysms, pseudoaneurysms, venous collaterals, and vascular malformations.^2- 3Vascular structures can be diagnosed with color Doppler imaging. The other entities can be excluded by evaluation with fine-needle aspiration or core needle biopsy. Miscellaneous other conditions could include cysts, abscesses, and tumors in the surrounding organs, such as a pancreatic pseudocyst or a mucinous cystic tumor extending into the splenic parenchyma. Although preoperative ultrasonography or, preferably, abdominal computed tomographic scan are helpful for determining both the cyst's site of origin and its relationship to surrounding structures, we were unable to determine the site of origin correctly in the present case because the cyst was located between the spleen and the pancreatic tail.

When a splenic cyst produces symptoms or is larger than 5 cm, or if the diagnosis is in question, surgical exploration or treatment is warranted. Total splenectomy, partial splenectomy, and cystectomy have been reported to be adequate treatments for these cysts. Limited treatments, such as catheter drainage or sclerosis, are associated with high rates of recurrence or infection and have largely been abandoned. Currently, the optimal treatment options are partial splenectomy, total cystectomy, marsupialization, or cyst decapsulation via either an open or a laparoscopic approach.³In the present case, the cyst was located in the splenic hilus, and the splenic parenchyma was reduced to a rim of tissue pushed to the periphery. Therefore, complete splenectomy was the only option.

Correspondence:Yoichi Ishizaki, MD, Department of Hepatobiliary-Pancreatic Surgery, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan (ishizaki@med.juntendo.ac.jp).

Accepted for Publication: October 21, 2006.

Author Contributions:Study concept and design: Ishizaki and Kawasaki. Acquisition of data: Omori. Analysis and interpretation of data: Ishizaki. Drafting of the manuscript: Omori, Ishizaki, and Kawasaki. Administrative, technical, and material support: Omori and Ishizaki. Study supervision: Kawasaki.

Financial Disclosure:None reported.