Canadian Association of Radiologists Journal xx (2012) 1e10www.carjonline.org

Abdominal Imaging / Imagerie abdominale

The Mysterious Organ. Spectrum of Focal Lesions Within the SplenicParenchyma: Cross-Sectional Imaging With Emphasis on Magnetic

Resonance Imaging

Najla Fasih, MBBS, FRCRa, Ajay Gulati, MDb,*, John Ryan, MD, FRCPCa, S. Ramanathan, MD,DNBb, Alampady Krishna Prasad Shanbhogue, MDc, Matthew McInnes, MD, FRCPCa,

David B. Macdonald, MD, FRCPCa, Margaret Anne Fraser-Hill, MD, FRCPCa,Cynthia Walsh, MD, FRCPCa, Ania Z. Kielar, MD, FRCPCa, Kanchan Bhagat, MDd

aDepartment of Diagnostic Imaging, The Ottawa Hospital, University of Ottawa, Ontario, CanadabPGIMER (Post Graduate Institute of Medical Education and Research), Chandigarh, India

cDepartment of Radiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USAdReligare SRL Limited, Faridabad, Haryana, India

Abstract

Incidental splenic lesions are frequently encountered at imaging performed for unrelated causes. Splenic cysts, hemangiomas, and

lymphomatous involvement are the most frequently encountered entities. Computed tomography and sonography are commonly used forinitial evaluation with magnetic resonance imaging reserved as a useful problem-solving tool for characterizing atypical and uncommonlesions. The value of magnetic resonance imaging lies in classifying these lesions as either benign or malignant by virtue of their signal-intensity characteristics on T1- and T2-weighted imaging and optimal depiction of internal hemorrhage. Dynamic contrast-enhancedsequences may improve the evaluation of focal splenic lesions and allow characterization of cysts, smaller hemangiomas, and hamarto-mas. Any atypical or unexplained imaging feature related to an incidental splenic lesion requires additional evaluation and/or follow-up.Occasionally, biopsy or splenectomy may be required for definitive assessment given that some of tumours may demonstrate uncertainbiologic behavior.

R�esum�e

On d�ecouvre souvent des l�esions �a la rate de mani�ere fortuite lors d’un examen d’imagerie r�ealis�e pour des causes non apparent�ees. Les

kystes spl�eniques, les h�emangiomes et les atteintes lymphomateuses figurent parmi les pathologies les plus fr�equemment relev�ees. Ona souvent recours �a la tomodensitom�etrie et �a l’�echographie pour effectuer une �evaluation initiale, l’imagerie par r�esonance magn�etiqueservant plutot d’outil de r�esolution de probl�emes pour caract�eriser les l�esions atypiques et inhabituelles. L’imagerie par r�esonance magn�etiquepermet de d�eterminer si les l�esions sont b�enignes ou malignes en raison des caract�eristiques de l’intensit�e du signal sur les images pond�er�eesen T1 et en T2 et de la repr�esentation optimale des h�emorragies internes. Les s�equences dynamiques rehauss�ees par un produit de contrastepeuvent par ailleurs faciliter l’�evaluation des l�esions focales spl�eniques et permettre la caract�erisation des kystes, des petits h�emangiomes etdes hamartomes. Un �el�ement d’imagerie atypique ou non expliqu�e li�e �a une l�esion spl�enique d�ecouverte par hasard exige une �evaluationsuppl�ementaire ou un suivi. Par ailleurs, il faut parfois recourir �a une biopsie ou �a une spl�enectomie pour obtenir une �evaluation ded�etermination puisque certaines tumeurs peuvent pr�esenter des manifestations biologiques de nature incertaine.� 2012 Canadian Associationof Radiologists. All rights reserved.

The spleen, since classical times, was considereda mysterious organ. However, the trend in the present erahas changed due to technologic advances such as multi-detector computed tomography (CT) and availability of

* Address for correspondence: Ajay Gulati, MD, The Ottawa Hospital,

General Campus, 501 Smyth Rd, Ottawa, Ontario K1S8L6, Canada.

0846-5371/$ - see front matter � 2012 Canadian Association of Radiologists. A

http://dx.doi.org/10.1016/j.carj.2012.03.004

higher field strengths in magnetic resonance imaging (MRI)[1]. Although metastatic and primary tumours of the spleenare relatively rare, radiologists need to be familiar withimaging features and enhancement patterns to categorize

E-mail address: drajaygulati@rediffmail.com (A. Gulati).

ll rights reserved.

Table 1

Focal lesions within the splenic parenchyma: criteria for diagnoses

Hamartoma Equivalent of focal nodular hyperplasia in the liver; isohypodense, well circumscribed, with avid

vascular enhancement that homogenizes on delayed phase images; isohyperintense on T2-weighted

sequences, with an enhancement pattern similar to that on CT; interval stability.

Hemangioma Typical features of hemangioma on dynamic contrast-enhanced CT or MRI, including hyperintensity

on T2-weighted and homogeneous or heterogeneous enhancement on delayed MRIs; may not demonstrate

peripheral nodular discontinuous coalescence of nodules commonly seen in their hepatic counterparts;

interval stability.

Lymphangioma Single or multiple, uniloculated or multiseptated lesions within the spleen, demonstrating low T1,

high T2 signal intensity; hypodense on CT; internal septae may be low signal on T2-weighted sequences

and enhance on postgadolinium sequences; peripheral lobulations may be seen.

Lymphoma or metastases Biopsy-proven malignancy at another, extrasplenic, location, with characteristic nodular splenic involvement

at CT or MRI that had been shown to be progressively enlarging or reducing in size with chemotherapy

at sonographic or CT follow-up.

Littoral cell angioma Classic appearance is that of innumerable confluent nodules within the splenic parenchyma that are low

attenuation on CT and low signal on T1- and T2-weighted MRIs due to intralesional hemosiderin; the

nodules enhance on portal venous phase images and become isodense to the splenic parenchyma on

delayed images; occasionally the tumour may be solitary; splenic biopsy is usually needed to

establish the diagnosis.

Bacterial abscess Typical features of a pyogenic abscess at contrast-enhanced CT include a hypoattenuating lesion with

ring enhancement and regression or resolution after antibiotic therapy at sonographic follow-up.

Fungal abscess History of immunosuppression combined with typical features of hepatosplenic candidiasis at CT, ie,

multiple small, low-attenuation concurrent hepatic and splenic lesions and complete or partial

resolution after antifungal therapy at sonographic and/or CT follow-up.

Parasitic cyst History of travel to an endemic area with positive serology for echinococcal disease combined with

typical features at CT; well-defined, nonenhancing, near-water attenuation multicystic mass and

regression or change in imaging appearance (ie, solid cystic lesion with calcifications) after

antiparasitic treatment at sonographic and CT follow-up.

Nodular sarcoidosis Extrasplenic histologic proof of noncaseating epithelioid granulomas combined with features at

contrast-enhanced CT or MRI compatible with a macronodular splenic sarcoidosis and regression

or disappearance at sonographic follow-up, either spontaneously or after steroid therapy.

Angiosarcoma Hypervascular, ill-defined large mass enlarging and distorting the spleen, with or without washout

and multiple tortuous internal vessels; variable signal intensity on T1- and T2-weighted sequences

due to the presence of hemorrhage or necrosis; occasionally present as splenic rupture with

hemoperitoneum and/or associated hepatic metastases.

CT ¼ computed tomography; MRI ¼ magnetic resonance imaging.

2 N. Fasih et al. / Canadian Association of Radiologists Journal xx (2012) 1e10

incidentally detected splenic lesions as benign or malignant.Other focal lesions and their mimics within the spleeninclude posttraumatic pseudocyst, splenic infarction, focalhemorrhage, inflammatory pseudotumour, abscess, Langer-hans cell histiocytosis, peliosis, Gandy-Gamna nodules,extramedullary hematopoiesis, and splenic involvementwith Gaucher disease. Sonography is the first and mostcommon modality in use and is sensitive in assessing thecystic nature of the lesion. Further evaluation may be per-formed with CT or MRI, depending on the availability ofequipment and expertise. CT is usually helpful in evaluatingthe lesion’s enhancement pattern, which is an importantdeterminant of the nature of the lesion. MRI has a similarrole to CT in detection and characterization. Dynamic MRIassesses the vascularity of the lesions and hence differen-tiates benign and malignant lesions. Recently, diffusionMRI is being evaluated in discrimination of splenic lesionssimilar to its established role in the liver. Diffusionrestriction can be seen in abscesses (tuberculous, pyogenic)and high apparent diffusion coefficient in vascular lesions,for example, littoral cell angioma [2,3]. Recent emergenceof contrast-enhanced ultrasound (CEUS) has demonstratedcomparable sensitivity to CT and MRI in evaluating theenhancement pattern of splenic lesions. CEUS has the added

advantage of offering real-time evaluation of lesionenhancement (Table 1) [4].

Benign Tumours

Most of the incidentally detected primary tumours of thespleen are benign and originate from the vascular endothelium.These include hemangioma, lymphangioma, hamartoma,littoral cell angioma, and hemangioendothelioma. Althoughthese neoplasms are uncommon, their importance lies in thatthey must be differentiated from the more common neoplasticdisorders, such as lymphoma and metastases [5]. Theenhancement pattern is the most commonly used feature todistinguish benign from malignant splenic lesions on contrast-enhanced CT and dynamic contrast MRI. Three majorenhancement characteristics that significantly correlate withbenignancy or malignancy of focal lesions within the spleenhave been identified on CEUS. A constantly nonenhancing orconstantly isoenhancing lesion is 100% positively predictivefor benignancy, whereas, a progressively hypoenhancing lesionis 87% positively predictive for malignancy [4]. However,CEUS is not beingwidely used due to cost and lack of expertise.

Presenting signs and symptoms are nonspecific, and patientsare frequently asymptomatic. Most of these tumours are

Figure 1. (A) Splenic hemangioma in a 35-year-old man detected incidentally on ultrasound performed for unrelated indication. Sagittal ultrasound Doppler

images through the left upper quadrant, revealing an echogenic lesion within the splenic parenchyma with internal vascularity. (B) Axial contrast-enhanced

computed tomography (CT) image, revealing a hypoattenuating lesion within the spleen (arrow). The enhancement characteristics are difficult to discern

on uniphasic CT. (C-E) Magnetic resonance imaging was performed for further characterization. The lesions are hyperintense on T2-weighted image (C),

demonstrating central areas of nodular enhancement (D), with homogeneous enhancement on delayed images (E). Findings are compatible with splenic

hemangiomas. Please note that the typical centripetal nodular enhancement seen in hepatic hemangiomas may not be seen. Stability in size and morphology

was demonstrated on follow-up imaging. (C-E) (Arrows) represent the dominant splenic lesion in this index case, which was a hemangioma.

3Focal splenic lesions: MR / Canadian Association of Radiologists Journal xx (2012) 1e10

discovered incidentally during imaging performed for unre-lated causes. Occasionally, however, the clinical presentationmay be dramatic because these lesions may cause spontaneousrupture of the spleen and subsequent hemoperitoneum.

Hemangioma

Hemangioma is themost commonbenignprimary neoplasmof the spleen [6].Most splenic hemangiomas are asymptomaticand congenital in origin and arise from the sinusoidal epithe-lium. The majority are less than 2 cm in diameter. Both capil-lary and cavernous-type lesions, with the latter being mostfrequent, are identified on histopathology. Depending on theirmorphologic characteristics, the radiologic appearance mayvary from solid to cystic; however, the most commonmorphology is a solid mass with cystic spaces. Sonographyusually demonstrates a well-circumscribed intrasplenicechogenic, solid, or, rarely, complex cysticmass, andmay showinternal vascularity (Figure 1A). The presence of calcificationsmay manifest as foci of acoustic shadowing. However, theseare rare.

On unenhanced CT, small hemangiomas appear as iso- tohypoattenuating well-circumscribed nodules within the

spleen (Figure 1B). After contrast administration, peripheralenhancement with centripetal progression noted in hepatichemangiomas may be seen. However, splenic hemangiomasalso may demonstrate discrete mottled areas of heterogenousenhancement rather than the typical centripetal enhancementseen within a hepatic hemangioma [5]. Splenic hemangiomasmay not have well-defined peripheral nodules that coalesceover time, which is likely secondary to the difference in thevascular supply of the background organ rather than inherentdifferences between splenic and hepatic hemangiomas.Therefore, the discontinuous peripheral enhancement notedin hepatic hemangiomas may be less prominent in splenichemangiomas during the arterial phase of contrast enhance-ment given that the background splenic enhancement canobscure this feature [7].

On MRI, these lesions are iso- to hypointense whencomparedwith the normal splenic parenchyma onT1-weightedimages and usually hyperintense on T2-weighted images. Aftergadolinium administration and dynamic contrast-enhancedMRI, variable patterns of enhancement discussed earlier maybe encountered (Figure 1, C-E). Large lesions may havea variable MRI appearance if complicated by hemorrhage orthrombosis. The larger lesions are therefore sometimes difficult

Figure 2. A 35-year-old patient with incidentally detected splenic hamartoma. (A) Sagittal Doppler ultrasound image, demonstrating a well-defined hypoechoic

splenic mass with increased, predominantly central, vascularity. (B, C) Axial arterial phase (B) and portal venous phase (C) computed tomography images

through the spleen. The lesion is hypervascular and optimally demonstrated on arterial phase only, being nearly isodense on portal venous phase (arrows). Note

the contour abnormality along the medial aspect related to mass effect. (D-G) Axial T2-weighted, pre- and postgadolinium T1-weighted fat-suppressed images

through the spleen. The lesion is isointense on T2-weighted (D) and T1-weighted (E), with intense enhancement on arterial phase (F) images, and it remains

hyperintense to the splenic parenchyma on delayed images (G). Rarely, a central scar may be seen, as in this case (G, thick arrow). Follow-up imaging

demonstrated no change in either the size or the morphology of this lesion, which confirmed its benign nature. (F) (Arrow) represents the enhancing part of the

lesion. (G) (Thin arrow) represents the enhancing part of the lesion on the delayed image.

4 N. Fasih et al. / Canadian Association of Radiologists Journal xx (2012) 1e10

to differentiate from malignant disease solely on the basis ofimaging findings [7].

Hamartoma

Hamartoma is a rare benign tumour of the spleen. Theautopsy incidence has been quoted as 0.13% in variousarticles [8]. Hamartomas may occur at any age and have nosex predilection. They usually are discovered as incidentalfindings. However, larger lesions may present with spleno-megaly and, rarely, rupture. Symptoms of splenic seques-tration, such as thrombocytopenia and anemia, may occur aswell. On pathologic examination, hamartomas representmalformations composed of disordered mixture of normalsplenic red pulp elements.

Sonography is arguably amore sensitivemodality thanCTindetecting the lesion, which typically appears as a well-circumscribed solid hyperechoic mass that may occasionally

show cystic components. Colour-Doppler sonography demon-strates a hypervascular lesion that contains multiple radialblood flow patterns (Figure 2A). In fact, hamartoma usuallymanifests as a hypervascular mass that is composed of arte-riovenous shunts, venous lakes, and aneurysmal dilatation ofvessels, characteristic of a typicalmalignant vascular pattern onangiography. This hypervascularity is reflective of the increasedblood supply of the red pulp within the hamartoma.

CTs demonstrate a well-demarcated, solid hypo- or iso-dense mass with characteristic findings of calcification or fattycomponents.Occasionally, hemosiderin depositionmay imparta hyperdense appearance on unenhanced images. Usually,these lesions are isoattenuating relative to the normal spleenbefore and after intravenous contrast (Figure 2,B andC),whichmakes them difficult to detect, and a contour abnormality maybe the only finding that suggests their presence.

On MRI, hamartomas are isointense when compared withthe splenic parenchyma on T1-weighted images, iso- to

Figure 3. (A) A 27-year-old man with splenic lymphangioma. Well-circumscribed hypoechoic, lobulated mass (thin arrow) with posterior acoustic

enhancement (arrowhead) in keeping with its cystic nature. Note echogenic intralocular debris (thick arrow). (B) Axial contrast-enhanced computed

tomography images, demonstrating a low-attenuation lesion within the splenic parenchyma (straight arrows). Note thin internal, septae (curved arrow). (C)

Axial T2 half-Fourier-acquisition single-shot turbo spin-echo (HASTE) magnetic resonance images, confirming the cystic nature. (C) (Arrows) indicate the

margins of the lesion. No solid components or mural nodules can be discerned. Stability in the size and appearance was demonstrated on follow-up imaging,

thereby confirming its benign nature.

5Focal splenic lesions: MR / Canadian Association of Radiologists Journal xx (2012) 1e10

heterogeneously hyperintense on T2-weighted images.Dynamic contrast-enhanced T1-weighted imaging depictsheterogenous enhancement on early postcontrast images [7].On delayed images, hamartomas are more homogeneous intheir enhancement (Figure 2, D-G). It is important todifferentiate these benign lesions from malignant nodules ofthe spleen, such as lymphoma and metastatic disease. Priorimaging if available is helpful in confirming stability andallowing them to be characterized as benign.

Lymphangioma

Splenic lymphangiomas and hemangiomas are closelyrelated vasoformative tumours. However, splenic lym-phangioma is much less common. It is most often detected asan incidental finding in children. These lesions may occur asa part of systemic lymphangiomatosis in young patients, and,hence, diagnostic evaluation should include extrasplenic

Figure 4. Littoral cell angioma in a 57-year-old man who presented with anemi

strating an enlarged spleen with a craniocaudal dimension of 17 cm. The echotex

contrast-enhanced computed tomography images, demonstrating hypoattenuati

enhancement is seen on the portal venous phase. A few of these demonstrate p

stained section of littoral cell angioma of spleen, showing vascular spaces (thick

organs [9]. Sonography demonstrates a well-defined cysticmass that may contain septae and intralocular echogenicdebris (Figure 3A). Colour-Doppler interrogation maydemonstrate vascularity along the cyst walls and septae.

CT findings include well-circumscribed, thin-walled,single or multiple areas of low attenuation that do not typi-cally enhance on postcontrast imaging (Figure 3B). Occa-sionally, small, linear, peripheral calcifications are noted. OnMRI, the lesions are cystic, with homogeneous low-signalintensity on T1-weighted images and high-signal intensityon corresponding T2-weighted images (Figure 3C).Proteinaceous fluid and/or internal hemorrhage may manifestas areas of high-signal intensity on T1-weighted sequences.

Littoral Cell Angioma

This rare vascular tumour of the spleen has been describedrelatively recently [10]. This lesion may occur at any age and

a and thrombocytopenia. (A) Sagittal grey-scale ultrasound images, demon-

ture is heterogeneous, with scattered hypoechoic nodules (arrows). (B) Axial

ng lesions of variable size (arrows) within the enlarged spleen. Variable

eripheral rim calcification. (C) Hematoxylin and eosin (magnification �20)

arrow) lined by plump endothelial cells (thin arrow).

Figure 5. A 35-year-old patient with lymphoma who presented with fever and constitutional symptoms. (A) Sagittal ultrasound image, demonstrating complex,

predominantly hypoechoic mass (arrow) within the spleen with scant vascularity. (B-D) The hepatic lesions appear hypointense on T1-weighted (B) and

hyperintense on T2-weighted (C) sequences. Splenic lesions are isointense on both T1-weighted (B) and T2-weighted (C) sequences. (D) Delayed postcontrast

images, revealing variable enhancement. Given its indeterminate nature, a biopsy was performed, which confirmed non-Hodgkin lymphoma. (B) (Arrow)

represents the hepatic lesion which is hypointense on T1. Note the splenic lesion in (B) is isointense and not distinctly seen from the normal splenic

parenchyma. (C, D) (Arrows) represent the hepatic and the splenic lesions.

6 N. Fasih et al. / Canadian Association of Radiologists Journal xx (2012) 1e10

has no sex predilection. Patients with littoral cell angiomausually present with symptoms of hypersplenism associatedwith laboratory evidence of anemia or thrombocytopenia.They may also present with constitutional symptoms andpyrexia of unknown origin. Splenomegaly usually is present.On histologic examination, the tumour arises from littoralcells that line the splenic red pulp sinuses. Anastomosingvascular channels with irregular lumina that feature cyst-likespaces lined with endothelial cells are present (Figure 4C). Ahistologic description reflects the radiologic appearance ofthis tumour, with splenomegaly and multiple round lesions ofsimilar shape and size diffusely distributed within the splenicparenchyma [5,10,11].

On sonography, the enlarged lobulated spleen may reflectheterogenous echotexture or multiple nodules with echoge-nicity close to that of the normal splenic parenchyma(Figure 4A). Discrete nodules may be invisible on unenhancedCT images. After contrast administration, these nodules appearas multiple hypoattenuating lesions on early portal venousphase and enhance homogeneously to become isodense to thesplenic parenchyma on late portal venous phase (Figure 4B).This delayed enhancement may help in narrowing the differ-ential diagnosis. On MRI, markedly low-signal intensity isusually demonstrated on both T1- and T2-weighted images.This appearance is classic and is reflective of intralesionalhemosiderin. Rare case reports of solitary lesions withoutT2-weighted hypointensity have been documented [10].Increased apparent diffusion coefficient values on diffusion-

weighted imaging have been observed in littoral cell angiomasimilar to other hepatic vascular lesions [2].

Malignant Tumours

Common splenic malignant lesions include lymphoma andmetastases. Uncommon tumours include angiosarcoma andchloroma. Apart from CT and MRI, positron emission tomog-raphy CT is useful in detecting and distinguishing malignantfrom nonmalignant splenic lesions. Fluorodeoxyglucose (FDG)avid lesions in a known case of FDG avid malignancy is highlysuggestive of metastases. Even in patients without knownmalignancy, FDG avid lesions were more often malignantlesions (80%). False positivity due tomoderate uptake in the caseof granulomatous diseases (tuberculosis, histoplasmosis) andnoninfectious inflammatory disorders (pseudotumour) needs tobe kept in mind, especially in cases without known malignancy[12].

Lymphoma

Lymphoma is the most commonmalignancy that affects thespleen as part of the spectrum of generalized lymphoma.Primary lymphoma of the spleen is rare. Non-Hodgkinlymphoma is the most common subtype. Splenomegaly isnoted in up to 80% of cases [1]. Sonography may depict an ill-defined, solitary inhomogeneously hypoechoic lesion(Figure 5A). Alternatively, generalized, diffuse inhomogeneity

Figure 6. Solitary splenic metastasis from malignant melanoma with spontaneous rupture and intraperitoneal hemorrhage.(A) Axial contrast-enhanced

computed tomography, demonstrating solitary, inhomogeneously enhancing lesion within the spleen (thick arrow); relatively high attenuation ascites is

compatible with hemoperitoneum (thin arrows). (B-D) Magnetic resonance imaging performed earlier to acute rupture. The lesion (thin arrows) reveals

isointense signal on T2 and T1-weighted images with foci of cystic change and/or necrosis (thick arrows). Enhancement is heterogeneous on postcontrast

images. Given its indeterminate nature on imaging, a biopsy was performed, which confirmed the lesion to be metastatic.

7Focal splenic lesions: MR / Canadian Association of Radiologists Journal xx (2012) 1e10

with subcentimeter hypoechoic lesions may be encountered.On CT, the appearance is very variable and includes homoge-neous enhancementwithout a discretemass,multifocal lesions,solitary mass, or diffuse infiltration. These tumours do notgenerally enhance, and they present as low attenuation lesionswith respect to the surrounding parenchyma. Lymph-nodeenlargement within the retroperitoneal-mesenteric recessesmay support the diagnosis.

Lymphomatous nodules tend to be isointense to splenicparenchyma on T1- and T2-weighted images, although theymay be hypointense on T2-weighted images (Figure 5, B-D)[2,6]. This feature is useful in differentiating them frommetastases, which are rarely hypointense on T2-weightedimages. Contrast material injection may improve lesiondetection. CEUS has been shown to increase the sensitivity ofdetection of lymphoma involvement of the spleen. Accordingto 1 study, CEUS detected almost double the number of splenicfoci of lymphomatous infiltration when compared with CT orFDG PET, which is of great clinical significance because itimpacts the lymphoma staging and the treatment strategy aswell. Lymphoma lesions appear as well-defined defects due to

rapid washout of contrast in sharp contrast to the enhancingsurrounding normal splenic parenchyma. [13].

Metastases

Splenic metastases are uncommon and represent 4%-7% ofthe focal lesions within the spleen [1,14]. Fifty percent ofmetastatic lesions to the spleen originate frommelanoma [15].Breast and lung cancers follow closely. Lesions may be soli-tary or multiple. Concurrent metastases to the liver and otherabdominal structures corroborate the diagnosis. On sono-graphic examination, metastases demonstrate a variableappearance but are generally hypoechoic. On CT, splenicmetastases typically are hypodense with inhomogeneouscontrast enhancement (Figure 6A). On MRI, metastases arecommonly isointense to the spleen on unenhanced sequences[6], although they can be hyperintense onT2-weighted images,particularly when necrosis or cystic change is present.Hemorrhagic metastases from melanoma, for example, candemonstrate high signal on T1-weighted images [2]. These 2features may be useful in distinguishing metastases from

Figure 7. (A) Axial contrast-enhanced computed tomography images, demonstrating a heterogeneous hypervascular mass within the spleen (thin arrows), with

hemoperitoneum (thick arrow). (B) Axial T2-weighted half-Fourier-acquisition single-shot turbo spin-echo (HASTE) image, demonstrating a heterogeneously

hyperintense mass (thick arrow) within the spleen. (C, D) Postgadolinium dynamic contrast-enhanced images and demonstrate mural enhancement, with

islands of internal hypervascularity (thin arrows). Most of the mass is necrotic secondary to previous therapeutic embolization. The lesion was biopsied, which

confirmed it to be angiosarcoma.

Figure 8. A hydatid cyst in a 62-year-old woman. (A) Ultrasound performed to assess the left upper quadrant mass detected on the chest radiograph shown

earlier. The lesion is of mixed echogenicity with scattered hypoechoic areas (long arrow). (B) Contrast-enhanced computed tomography, revealing mural

calcifications (straight arrows) with a low-attenuation interior (curved arrow). (C-E) The calcified cyst wall is hypointense on T2-weighted images (C, thin

arrow), with subtle hyperintensity on T1-weighted images (D, arrow). Internal loculations are well depicted on T2-weighted images (C, thick arrow). There is

no enhancement (E, arrow) on any of the multiphasic postcontrast phases (E). Stability was demonstrated on follow-up imaging, with no change either in the

size or the morphology of this lesion, which confirmed its benign nature.

8 N. Fasih et al. / Canadian Association of Radiologists Journal xx (2012) 1e10

Figure 9. A 45-year-old woman with known sarcoidosis. (A) Axial contrast-enhanced computed tomography image, demonstrating multiple tiny hypoattenuating

lesions within the spleen (arrows). (B-E) Lesions reveal low signal intensity on T2-weighted (B) and early postcontrast fat-saturated T1-weighted arterial (C) and

portal venous phase (D) dynamic magnetic resonance sequences. Homogeneous enhancement is seen on delayed images (E). This finding is sometimes seen with

granulomatous lesions. Follow-up imaging demonstrated no change in either the size or the morphology of these lesions thereby confirming their benign nature.

(B) (Arrows) indicate the granulomatous lesions appearing hypointense on T2. (C, D) (Arrows) show that some of these lesions which appear hypointense on

the early dynamic post contrast sequences. (E) (Arrows) indicate that most of the lesions show homogeneous enhancement on the delayed image.

9Focal splenic lesions: MR / Canadian Association of Radiologists Journal xx (2012) 1e10

lymphoma. The latter rarely demonstrates necrosis orhemorrhage. Contrast enhancement within metastatic lesionsusually is inhomogeneous (Figure 6, B-D). MRI, whendepending on the presence of internal necrosis and hemor-rhage, may be more accurate for detection of metastases andprovide a clue towards the origin of the primary tumour.

Angiosarcoma

Angiosarcoma is a very rare vascular malignant tumour ofthe spleen. The average age of presentation varies between 40and 60 years. There is no sex predilection. Interestingly, there isno documented association of splenic angiosarcomas withcarcinogenic exposure to thorium dioxide, vinyl chloride, orarsenic, unlike hepatic angiosarcomas. The tumour is highlyaggressive, with a poor prognosis [16]. Patients may presentwith nonspecific constitutional symptoms and weight loss.Occasionally, spontaneous rupture of the affected spleen maypresent as a life-threatening emergency, with signs and symp-toms of hemoperitoneum. Metastases from angiosarcoma arecommonly seen and usually affect the liver, lungs, and bones.

Most commonly encountered is an aggressive mass thatdiffusely infiltrates and enlarges the spleen. CT (Figure 7A)

demonstrates a poorly circumscribed, inhomogeneous massof variable echogenicity and mixed attenuation. Contrastenhancement is variable and usually heterogeneous,depending on the presence of hemorrhage and necroticdegeneration. Associated hemoperitoneum may be observedin the unfortunate event of tumour rupture. MRI appearanceis dependant upon the presence of internal hemorrhage andnecrosis. Areas of increased and decreased signal intensityon both T1- and T2-weighted sequences suggest the presenceof blood products and necrosis, respectively. Low signalintensity areas on MRI may represent hemosiderin deposi-tion. Dynamic contrast-enhanced imaging clearly depictsheterogeneous enhancement that corresponds to the hyper-vascular nature of the tumour (Figure 7, B-D) [6].

Miscellaneous Lesions

Echinococcal or Hydatid Cyst

Hydatid disease is caused by the larval form of echino-coccus granulosus. Humans are the accidental intermediatehost. Splenic involvement is rare site and occurs in 2% ofcases; the liver and lungs being common locations [17].

10 N. Fasih et al. / Canadian Association of Radiologists Journal xx (2012) 1e10

Clinical presentation is nonspecific. On sonography,nonspecific findings of simple or complex splenic cyst areseen. Different sonographic patterns are described; theseinclude internal membranes, hydatid sand, scolices daughtercysts, and cyst wall calcification associated with acousticshadowing. The latter may prevent complete evaluation ofcyst (Figure 8A). On CT, well-circumscribed hypodenselesions of fluid attenuation are usually identified with noenhancement on postcontrast imaging (Figure 8B). Hydatidsand and debris may lead to increased CT attenuation.Peripheral calcifications are better appreciated on CT. MRI isused as a problem-solving tool in confirming the cysticnature of the lesion and confirmation of the lack ofenhancement (Figure 8, C-E).

Sarcoidosis

Splenic involvement in sarcoidosis is usually asymp-tomatic. Sarcoidosis involves the spleen in 38%-77% ofcases. Splenomegaly is the most common finding seen in30% of cases [18]. Multiple nodules that coalesce to formlarger nodules is the second most common finding. Sarcoidnodules appear as diffusely scattered, hypoechoic lesionson ultrasound and hypodense on CT. They range in sizefrom 2 mm to 2 cm, with no significant enhancement onpostcontrast images (Figure 9A). On MRI, sarcoid nodulesare hypointense on T1- and T2-weighted sequences, beingoptimally delineated on T2-weighted and early post-contrast images. The nodules may be inconspicuous ondelayed postcontrast images (Figure 9, B-E). Chest radio-graphs can be normal in up to 25% of cases with splenicinvolvement [19].

Conclusion

A variety of histologically diverse focal lesions may beencountered within the splenic parenchyma, although theirexact nature may sometimes be difficult to determine. MRIcan help in classifying these lesions as either benign ormalignant by virtue of their signal intensity characteristicsand contract enhancement patterns. Occasionally, percuta-neous biopsy may be necessary when focal lesions withatypical appearances, uncommon vascular lesions, or sus-pected malignant lesions are encountered.

References

[1] Giovagnoni A, Giorgi C, Goteri G. Tumours of the spleen. Cancer

Imaging 2005;5:73e7.

[2] Ertan G, Tekes A, Mitchell S, et al. Pediatric littoral cell angioma of the

spleen: multimodality imaging including diffusion-weighted imaging.

Pediatr Radiol 2009;39:1105e9.

[3] Lim J, Yu JS, Hong SW, et al. A case of mass-forming splenic tuber-

culosis: MRI findings with emphasis of diffusion-weighted imaging

characteristics. J Korean Med Sci 2011;26:457e60.

[4] Stang A, Keles H, Hentschke S, et al. Differentiation of benign from

malignant focal splenic lesions using sulfur hexafluoride-filled

microbubble contrast-enhanced pulse-inversion sonography. AJR Am

J Roentgenol 2009;193:709e21.

[5] Luna A, Ribes R, Caro P, et al. MRI of focal splenic lesions without

and with dynamic gadolinium enhancement. AJR Am J Roentgenol

2006;186:1533e47.

[6] Hayasaka K, Tanaka Y, Kawamori J. Dynamic MR imaging of splenic

tumor. Comput Med Imaging Graph 1997;21:243e51.

[7] Abbott RM, Levy AD, Aguilera NS, et al. From the archives of the

AFIP: primary vascular neoplasms of the spleen: radiologic-pathologic

correlation. Radiographics 2004;24:1137e63.

[8] Yu RS, Zhang SZ, Hua JM. Imaging findings of splenic hamartoma.

World J Gastroenterol 2004;10:2613e5.

[9] Chang WC, Liou CH, Kao HW, et al. Solitary lymphangioma of the

spleen: dynamic MR findings with pathological correlation. Br J Radiol

2007;80:e4e6.[10] Tatli S, Cizginer S, Wieczorek TJ, et al. Solitary littoral cell angioma of

the spleen: computed tomography and magnetic resonance imaging

features. J Comput Assist Tomogr 2008;32:772e5.

[11] Kinoshita LL, Yee J, Nash SR. Littoral cell angioma of the spleen:

imaging features. AJR Am J Roentgenol 2000;174:467e9.

[12] Metser U, Miller E, Kessler A, et al. Solid splenic masses: evaluation

with 18F-FDG PET/CT. J Nucl Med 2005;46:52e9.[13] Picardi M, Soricelli A, Pane F, et al. Contrast-enhanced harmonic

compound US of the spleen to increase staging accuracy in patients

with Hodgkin lymphoma: a prospective study. Radiology 2009;251:

574e82.[14] Gencosmanoglu R, Aker F, Kir G, et al. Isolated metachronous splenic

metastasis from synchronous colon cancer.World J SurgOncol 2006;4:42.

[15] Murphy JF, Bernardino ME. The sonographic findings of splenic

metastases. J Clin Ultrasound 1979;7:195e7.[16] Thompson WM, Levy AD, Aguilera NS, et al. Angiosarcoma of the

spleen: imaging characteristics in 12 patients. Radiology 2005;235:

106e15.

[17] Franquet T, Montes M, Lecumberri FJ, et al. Hydatid disease of the

spleen: imaging findings in nine patients. AJR Am J Roentgenol 1990;

154:525e8.

[18] Kessler A, Mitchell DG, Israel HL, et al. Hepatic and splenic

sarcoidosis: ultrasound and MR imaging. Abdom Imaging 1993;18:

159e63.

[19] Warshauer DM. Splenic sarcoidosis. Semin Ultrasound CT MR 2007;

28:21e7.