Splenic cyst

Splenic epithelial cysts, also referred as splenic epidermoidcysts or primary splenic cysts, are usually an innocuous incidental finding on imaging. They represent about 20% of the cysts found in the spleen. On imaging, they present as a unilocular fluid lesionlesions with thin and smooth walls and no enhancement.

Please note that secondary splenic cysts, in particular, splenic pseudocysts, which correspond to about 80 They represent ~20% of cysts seenfound in the spleen, will be discussed separately in specific articles for each aetiology, as describedand are usually an innocuous incidental imaging finding.

Note that most (~80%) simple-appearing cystic splenic lesions represent secondary cysts or pseudocysts (see Differential Diagnosis section below in the differentials section). 

Terminology

Although includingIn practice, both primary and secondary causes under the term spleniccysts are often described simply as "splenic cyst," for the sake of simplicity and accordance with radiological practice, this article will take it as a synonym for splenic epithelial cystoften the specific etiology is not evident.

Epidemiology

They are thought to account for 20% of benign non-parasitic cysts of the spleen ^5,8. There may be an increased female predilection.

Clinical presentation

The clinical presentation can vary ranging from being incidentally discovered on routine imaging to having nausea, vomiting, vague abdominal pain or rarely painful splenomegaly, particularly when the cysts are large. 

Pathology

They are congenital in origin. As “true” cysts, they have an epithelial lining formed secondary to the unfolding of peritoneal mesothelium or collections of peritoneal mesothelial cells trapped within the splenic sulci. A genetic defect of mesothelial migration is considered the cause. While most are sporadic, rarely there is a familial occurrence. They typically grow slowly and are usually large (around 10 cm) at the time of discovery. They are solitary in 80%. Peripheral calcifications are uncommon (10-15%).

Radiographic features

Ultrasound

Usually shows an anechoic to hypoechoic well defined intrasplenic lesion. Internal echoes may be present due do debris. Their margin may be echogenic with distal shadowing due to calcifications ⁸. 

CT 

Typically shows a hypoattenuating relatively well-defined intrasplenic lesion. The wall is thin and has a sharp demarcation to the splenic parenchyma. There is no rim or internal enhancement. Wall calcification may be present.

MRI

Well-defined cystic lesions with internal homogeneous fluid signal intensity: 

• T1: low signal intensity
• T2: very high signal intensity 

Treatment and prognosis

Small and asymptomatic cysts do not require treatment or followup. Symptomatic cysts are managed surgically.

Complications

Complications are rare and include haemorrhage, rupture and infection ^6,7.

Differential diagnosis

A number of splenic lesions may appear cystic, depending on the modality:

• secondary cysts (~80% of all splenic cysts)
  • splenic pseudocysts
    • post-traumatic pseudocyst: the end stage of splenic haematoma with resultant liquefactive necrosis and cystic changes
    • post-infarction pseudocyst: also resultant from liquefactive necrosis 
    • intrasplenic pancreatic pseudocyst
  • infection
    • splenic hydatid cyst
• other congenital cystic lesions (tend to be unilocular in a majority of cases)
  • splenic lymphangioma
  • splenic haemangioma
• splenic bacterial abscess
• cystic splenic metastases
• splenic lymphoma - although may appear nearly anechoic, hypoechoic lymphoma tends to have less distinct margins than a cyst ¹⁰