From our institution’s database,
we have selected the most characteristic cases of splenic cystic lesions,
some of them confirmed by pathological examination.
For each kind of lesion,
imaging features are presented and correlated with the findings reported in the available literature,
which are resumed in table 1 at the end of this section,
regarding their number,
the appearance of their wall and the presence or absence of septa and peripheral calcifications.
“SPLENIC CYSTS”
Both epidermoid and pseudocysts are usually simple spherical cystic lesions in imaging,
with an imperceptible wall [5,
4-6],
the pseudocysts being more likely to present peripheral calcifications,
internal debris and,
sometimes,
a thicker wall [6].
Fig. 1: US scan of a patient, who presented with left upper quadrant pain, revealed a rounded large (14 cm) cystic unilocular mass, with non-pure content.
Fig. 2: Unenhanced CT scan of the same patient as in figure 1, confirmed the imperceptible wall and low-attenuation content of the lesion. Both studies were suggestive of an epidermoid cyst, which was later confirmed by pathological examination.
Fig. 3: Contrast-enhanced CT scan of a patient, who had had an acute pancreatitis diagnosed six weeks earlier, later complicated by peripancreatic fluid collections formation, showed two rounded, well-defined, capsulated cystic masses, one in the pancreas’ tail and the other in the spleen, corresponding to pseudocysts.
Fig. 4: Another “false” cyst detected in a patient who had had a blunt abdominal trauma one month earlier, its wall being thinner than that of the lesion shown in figure 3, since a shorter period of time had passed since the lesion had begun to form.
Hydatid cysts are typically thick-enhancing-walled cysts with ring-like peripheral calcifications and inner “daughter cysts” at Computed Tomography (CT),
which walls produce a septated appearance at Ultrasonography (US) [2,
3-6].
Fig. 5: Primary splenic hydatidosis in a 24-year-old woman, who underwent imaging examinations because of pain in the left hypochondrium and a palpable mass. US scan showed a solitary complex cystic lesion in the spleen, with “daughter” cysts within it.
Fig. 6: The same lesion as in figure 5 at contrast-enhanced CT, appeared as a low-attenuation mass with “daughter” cysts within it.
Fig. 7: Note the incipient calcification of the hydatid cyst’s wall described in figures 5 and 6.
OTHER NONNEOPLASTIC SPLENIC CYSTIC LESIONS
Pyogenic Abscess
Abscesses appear as single or multiple cystic lesions,
which walls may be irregular and thickened,
eventually containing fluid-fluid or air-fluid levels,
although air is absent in the majority of cases.
At CT,
the most reliable method for their detection,
the wall may enhance with contrast medium if a capsule has developed.
[5,
6,
8]
Fig. 8: The spleen of a septic patient replaced by a low-attenuation and slightly heterogeneous mass, with enhancing wall at contrast-enhanced CT, representing the complete liquefactive necrosis of the organ due to infarction followed by superimposed infection.
Infarction
Occasionally,
splenic infarctions might be cystic,
especially in the subacute phase and when liquefactive necrosis occurs [6].
Typically,
they present as wedge-shaped peripheral areas,
hypoechogenic at US and of low attenuation at CT,
with no enhancement after contrast administration [5,
6,
8,
9].
Initially they have an increased volume due to edema,
progressively becoming more rounded and better delineated and,
finally,
a fibrotic parenchymal defect [5,
6,
8].
Fig. 9: Splenic infarct in a 56-year-old patient with chronic hepatic disease (CHD) and splenomegaly. Contrast-enhanced CT revealed a nonenhancing hypodense area, wedge-shaped and of fluid attenuation in its left portion, representing hemorrhagic necrotic tissue.
Fig. 10: Note the subcapsular fluid-fluid level in the inferior half of the spleen, adjacent to the infracted area described in figure 9, corresponding to subcapsular hemorrhage, which suggests a higher risk of rupture. The lobulated contour of the liver is due to CHD.
Hematoma
Splenic hematomas are usually identified as subcapsular crescentic or lenticular,
well demarcated areas causing some flattening of the normally convex border of the spleen,
which are hypoechogenic at US,
spontaneously hyperdense and nonenhancing,
respectively at unenhanced and contrast-enhanced CT [3,
6,
9].
Fig. 11: Splenic subcapsular hematoma after a blunt abdominal trauma. Contrast-enhanced CT showed a lenticular non-enhancing area of low-attenuation along the posterior margin of the spleen with indentation of its border, which is normally convex.
NEOPLASTIC SPLENIC CYSTIC LESIONS
BENIGN
Hemangioma
Splenic hemangiomas’ appearance in imaging examinations range from predominantly solid,
to mixed,
to purely cystic.
Solid areas demonstrate a delayed centripetal nodular enhancement at contrast-enhanced CT [3,
5,
6,
8] and might show blood flow at colour-Doppler [11].
Scattered punctate or peripheral curvilinear calcifications might be present [3,
6,
8].
Fig. 12: Splenic hemangioma incidentally detected at an US scan in an asymptomatic patient, seen as a large multiloculated anechogenic lesion with posterior acoustic enhancement.
Fig. 13: A contrast-enhanced CT scan of the same patient as in figure 13, showed the multiloculated cystic lesion with enhancing septa and a small focus of calcification in its right posterolateral wall.
Lymphangioma
Lymphangiomas of the spleen may present as uni or multilocular sharply marginated cysts,
with a thin wall,
sometimes with marginal linear calcifications.
They appear as hypoechogenic masses,
frequentely septated and with occasional internal debris at US,
and do not enhance at contrast-enhanced CT [3,
6].
MALIGNANT
Lymphoma
Splenic lymphomatous involvement might have three basic pathological patterns with correspondent imaging features:
(a) infiltrative,
seen as splenomegaly without definite focal lesions;
(b) miliary,
with small (< 2 cm) scattered nodules,
sometimes markedly hypoechogenic resembling cyst,
but without acoustic enhancement at US; CT appearance is multifocal low-attenuation lesions,
which do not enhance after contrast administration;
(c) massive,
showing a solitary or multiple large lymphomatous mass with similar imaging characteristics to those of the military nodules.
[5,
6,
8]
Greater accuracy in the diagnosis may be obtained by demonstrating adenopathy in splenic hilum [3].
Fig. 14: Marginal zone B-cell non-Hodgkin lymphoma in a 71-year-old man, who underwent elective splenectomy because of severe thrombocytopenia, due to hypersplenism. The previous CT scan showed a solitary well-delineated round lesion of low attenuation in the upper pole of the spleen, which did not enhance after contrast administration. This lesion, proved to correspond to the lymphomatous mass in pathological examination, mimicked a splenic cyst.
Metastases
Splenic metastases usually appear as cystic ill-defined nodules,
frequently with internal debris at US and some degree of peripheral enhancement at CT after contrast administration [6,
8].
Sometimes they have internal septa,
which also enhance [6,
13].
Fig. 15: Multiple splenic cystic metastases of breast adenocarcinoma in a 87-year-old woman, seen as small low-attenuation nodules with irregular contours, one of those septated.
Fig. 16: A coronal slice of the same CT scan as in figure 16, shows how numerous the metastases are. Note the slight enhancement of their wall after contrast administration.
Table 1: Main characteristic imaging features of splenic cystic lesions, according to their origin. Adapted from table 2 of reference 6 in correlation with our series’ findings. S: single; M: multiple; +: present; ∅: absent; Sm: thin and smooth; I: thick and irregular.