NONPARASITIC cysts of the spleen can be divided into two categories, capsular and parenchymatous cysts, depending on the relationship of the cysts to the splenic capsule. The parenchymatous category includes epidermoids, cystic angiomas, and large unilocular fibrous-walled cysts of uncertain origin (this type of cyst is also referred to as a false cyst, with the implication that it is secondary to trauma or hemorrhage). The term "true cysts" refers to cysts with a specific type of lining cell other than fibroblasts.
Cysts of the spleen are unusual; Ferris and associates1 reported that only 19 cystic spleens were removed surgically at the Mayo Clinic over a period of 46 years and only one of the 19 surgical specimens exhibited a line of squamous, keratinizing epithelium. Tamaki2 was unable to find a single case of splenic cyst in the surgical file of the Jefferson Medical College Hospital for the years