Cystic lesions of the spleen are rare,
occurring less often than in other abdominal viscera [1].
Most are benign and found incidentally at radiologic examination.
Occasionally,
they may become symptomatic,
causing a left upper quadrant painful mass,
by the extrinsic mass effect on adjacent organs or,
less commonly,
by developing complication features of hemorrhage,
rupture,
or superimposed infection,
these usually coursing with fever and inflammatory laboratory parameters,
being effectively treated by splenectomy [2,
3] or by percutaneous fine-needle aspiration and drainage in selected cases [4].
In addition to “splenic cysts”,
there is a range of other lesions with a predominantly cystic appearance,
which etiology may be congenital,
inflammatory,
posttraumatic,
vascular or neoplastic [6,
7].
“SPLENIC CYSTS”
The lesions commonly designated as “splenic cysts” include the “true” and the “false” or posttraumatic ones,
which can only be definitely differentiated by the microscopic demonstration of the existence or lack of a cellular epithelial lining.
“True” cysts,
epithelium-lined,
are rare and might be nonparasitic and congenital (epidermoid),
or have a parasitic origin,
almost solely echinococcal (hydatid).
Hydatid cysts are very uncommon in the spleen and mostly caused by Echinococcus granulosus.
They are three layered structures,
with an outer wall of reactive parenchyma (pericyst),
a middle acellular laminated membrane (ectocyst) and an inner germinative layer,
where the larval stage of the parasite is produced and from which the “daughter cysts” are formed.
“False” cysts,
by far the most frequent ones,
are non-epithelium-lined lesions often associated with trauma,
including the called pseudocysts,
which are composed of localized areas of inflammatory and reparative fibroblastic changes.
[2,
3,
5,
6,
8]
OTHER NONNEOPLASTIC SPLENIC CYSTIC LESIONS
Pyogenic Abscess
Besides the possible superinfection of a prior existing splenic cyst,
localized pus collections with necrotic tissue can form in splenic parenchyma,
mostly by the hematogenous spread of a systemic infection (75%),
but also by penetrating trauma (15%) or prior splenic infarction (10%) [2,
3,
6,
8].
Their frequency has partially been increasing because of the rising number of people with immunocompromised systems,
whether secondarily to chemotherapy treatments,
drug abuse or acquired immunodeficiency syndrome [5].
They are non-capsulated structures,
which might progressively involve the surrounding tissue and sometimes rupture to subcapsular or perisplenic spaces [3,
6].
Infarction
Splenic infarction is usually due to involvement of splenic vessels by atherosclerosis,
tumor,
pancreatitis,
systemic emboli or sickle disease,
splenomegaly being a predisposing factor to thrombosis of the sinusoids.
They can be asymptomatic or present with local pain.
Superimposed infection easily occurs.
[5,
6,
8]
Hematoma
Splenic hematomas,
which may present with local pain,
consist of extravasated blood within the parenchyma or between the border of the spleen and its capsule.
They often occur in a traumatic context [2,
3,
6,
9],
the spleen being the most frequentely injured intraperitoneal organ in blunt abdominal trauma,
sometimes resulting in frank splenic laceration [3].
Anticoagulation therapy is another potential cause [6,
9].
NEOPLASTIC SPLENIC CYSTIC LESIONS
BENIGN
Hemangioma
Although very rare,
hemangioma is the most common primary neoplasm of the spleen [3,
5,
6,
8,
10],
with a reported prevalence of 0,3-14% [10].
Pathologically,
the lesion consists of endothelial-lined,
blood-filled spaces of varying size,
cystic areas with serous or hemorrhagic contents being much more common in splenic hemangiomas than in hepatic ones [6].
Most are single,
small and asymptomatic,
unless they rupture or grow enough to cause splenomegaly,
resulting in pain and,
less frequently,
in coagulopathy [3].
Lymphangioma
Lymphangioma is another rare vascular tumor similar to hemangioma,
although filled with lymph instead of erythrocytes,
also being asymptomatic in most of cases [2,
3,
6].
MALIGNANT
Lymphoma
Spleen,
as the largest lymphoid organ in the body,
is frequently involved in lymphomas [3,
5,
6,
8,
9],
either Hodgkin or non-Hodgkin,
these being the most common malignant splenic neoplasms,
mainly as a manifestation of a systemic disease instead of a primary one [3,
6,
9].
Clinical manifestations include fever,
left upper quadrant pain and splenomegaly [6].
They may become cystic due to massive internal necrosis and,
occasionally,
get secondarily infected resulting in abscess formation [6].
Metastases
Metastatic involvement of the spleen occurs in only 7% of patients with widespread malignancy,
melanoma being the source of 50% of cases [8] and breast adenocarcinoma the second most common origin [12].
They usually become symptomatic only when large.
Their cystic transformation is frequent [5,
6,
8] due to rapid growth with autoinfarction and/or internal necrosis [6].