Mesothelial cyst of the spleen mimicking a metastasis: a case report.

Mesothelial cyst of the spleen is a developmental disorder. Previous reports have elaborated on the radiological features of splenic mesothelial cysts as being unilocular with a smooth and well-defined margin. However, due to its rarity, it is unclear whether these characteristics are representative and specific for the diagnosis of mesothelial cysts. Herein, this case report presents an atypical case of splenic mesothelial cyst mimicking a malignant tumour, especially splenic metastasis in a 66-year-old woman with ascending colon cancer. Due to an overlapping imaging finding of hypodense splenic lesions, and considering the clinical history, a mesothelial cyst that developed as a multilocular hypodense mass from an ill-defined small nodule was inevitably misdiagnosed as metastasis. Although rare, it is important to consider the possibility of mesothelial cyst in a patient with multilocular hypodense lesions of the spleen.