Littoral cell angioma (LCA) is a rare vascular neoplasm arising from the littoral cells lining the red pulp sinusoids of the spleen. It is generally considered benign but low-grade malignant potential is debated. Histopathologically, it consists of anastomosing vascular channels lined by a unique cell type that expresses both endothelial and histiocytic markers — the CD31(+), CD68(+), and CD8(+) triple positivity is pathognomonic. Most patients are asymptomatic; symptomatic cases may present with splenomegaly, left upper quadrant pain, anemia, and thrombocytopenia. Erythrocytes are parasitized with hemosiderin accumulation — this hemosiderin deposit is a key imaging determinant. Lesions are typically multiple, small (usually <2 cm), and diffusely distributed throughout the splenic parenchyma. Association with autoimmune diseases and visceral organ malignancies has been reported. Definitive diagnosis typically requires histopathological and immunohistochemical examination after splenectomy. Increased uptake on Tc-99m sulfur colloid scintigraphy is characteristic because littoral cells demonstrate reticuloendothelial function.
Age Range
30-70
Peak Age
50
Gender
Equal
Prevalence
Rare
Littoral cell angioma arises from neoplastic proliferation of littoral cells lining the sinusoids of the splenic red pulp. Littoral cells are unique cells specific to the spleen that express both endothelial (CD31, FVIII-RA) and histiocytic/macrophage (CD68, lysozyme) phenotypes — this dual phenotype reflects the spleen's 'open circulation' system, where blood cells are subjected to phagocytosis and filtration by littoral cells as they pass through the sinusoids. Neoplastic proliferation of these cells creates anastomosing vascular channels within which erythrocyte phagocytosis continues — intracellular hemosiderin accumulation forms the pathological basis of imaging findings. Hemosiderin contains iron (Fe3+) and exhibits superparamagnetic properties: it causes marked signal loss (hypointensity) on T2 and T2*-weighted MRI — this results from hemosiderin disrupting local magnetic field homogeneity and accelerating proton spin-spin decoherence. On CT, hemosiderin accumulation creates mildly hyperdense appearance. The preserved reticuloendothelial function of littoral cells enables uptake of Tc-99m sulfur colloid and superparamagnetic iron oxide particles (SPIO) through phagocytosis — this property provides a diagnostic clue as increased uptake/signal loss on scintigraphy and SPIO-MR, distinguishing LCA from other vascular tumors.
The pathognomonic dual finding of LCA: (1) marked hemosiderin-related hypointensity on MRI T2 ('dark dots') and (2) increased uptake on Tc-99m sulfur colloid scintigraphy ('hot spots'). This combination is specific to LCA — hemangioma shows T2 hyperintensity + cold defect, lymphoma shows T2 hypointensity + cold defect.
On unenhanced CT, multiple, small, well-defined hypodense lesions are seen throughout the splenic parenchyma. Density typically ranges between 25-40 HU. Distribution is generally diffuse and homogeneous — creating a miliary pattern. Some lesions may show mildly hyperdense foci or isodense appearance due to hemosiderin accumulation. Splenomegaly accompanies most cases. Lesions are generally <2 cm. The splenic capsule is smooth without invasive features.
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Diffusely distributed, multiple, small hypodense lesions are seen throughout the splenic parenchyma in the setting of splenomegaly.
In the portal venous phase, lesions begin to become partially isodense to splenic parenchyma with peripheral enhancement. Small lesions (<1 cm) may become completely isodense in this phase — 'vanishing' phenomenon. In larger lesions, the center has not yet completely filled. On delayed phase (3-5 minutes), the majority of lesions become isodense to splenic parenchyma — this pattern is characteristic for LCA and reflects a tumor originating from the spleen's own circulation.
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The splenic lesions demonstrate progressive enhancement becoming isodense to splenic parenchyma on portal venous phase.
On T2-weighted MRI, lesions appear markedly hypointense relative to splenic parenchyma — this is the most characteristic and diagnostically most valuable MR finding of LCA. Hypointensity results from the superparamagnetic effect of hemosiderin accumulation. On T2* (gradient echo) sequences, hypointensity becomes more pronounced with 'blooming artifact'. Lesions create a 'black dots' appearance with miliary distribution pattern throughout the splenic parenchyma. In larger lesions, heterogeneous signal may be seen — hemosiderin-rich areas hypointense, hemosiderin-poor vascular areas isointense or mildly hyperintense.
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Multiple, diffusely distributed, markedly hypointense lesions are seen in the splenic parenchyma on T2W MRI, consistent with hemosiderin accumulation.
On T1-weighted MRI, lesions appear isointense or mildly hyperintense to splenic parenchyma. T1 hyperintensity is related to the paramagnetic effect of hemosiderin — Fe3+ ions can cause T1 shortening at low concentrations. T1 hyperintense foci may be seen with methemoglobin presence. Post-gadolinium contrast-enhanced T1 sequences show progressive enhancement pattern similar to CT.
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The splenic lesions show isointense to mildly hyperintense signal relative to splenic parenchyma on T1W MRI.
On Tc-99m sulfur colloid scintigraphy, splenic lesions show increased radionuclide uptake — this finding has critical diagnostic importance in differentiating LCA from other vascular tumors. The preserved RES function of littoral cells enables uptake of sulfur colloid particles through phagocytosis. Combined sulfur colloid + labeled erythrocyte study is nearly pathognomonic: increased uptake in both studies reflects dual RES and vascular function of littoral cells. Hemangioma shows no sulfur colloid uptake (endothelial cells do not perform phagocytosis).
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Increased radionuclide uptake is seen in the splenic lesions on Tc-99m sulfur colloid scintigraphy, consistent with preserved reticuloendothelial function.
On B-mode ultrasonography, multiple, small, well-circumscribed, homogeneously hypoechoic lesions are seen throughout the splenic parenchyma. Sizes typically range between 5-20 mm. Some lesions may show hyperechoic foci related to hemosiderin accumulation. Distribution is generally diffuse and random — may resemble miliary form of lymphoma or metastasis. Splenomegaly accompanies most cases. Color Doppler may show low-flow vascularity within lesions but Doppler signal may not be detectable in small lesions.
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Diffusely distributed, multiple, small, hypoechoic lesions are seen in the splenic parenchyma in the setting of splenomegaly.
Criteria
Diffusely distributed, multiple, small (<2 cm) lesions. Most common form. Splenomegaly accompanies.
Distinct Features
Typical miliary distribution in all modalities. Homogeneously T2 hypointense 'black dots' on MRI. No single dominant lesion.
Criteria
One or several large dominant lesions (>2-3 cm) with surrounding small miliary lesions. Rarer form.
Distinct Features
Large lesions may show heterogeneous signal. May mimic malignant lesion — biopsy/splenectomy more frequently required.
Criteria
Concurrent or sequential visceral organ malignancy or hematologic malignancy. Concurrent malignancy reported in 20-30% of cases.
Distinct Features
Imaging findings do not differ from classic type. Clinical context important — sulfur colloid scintigraphy critical in differentiating from metastasis.
Distinguishing Feature
Lymphoma shows cold defects on Tc-99m sulfur colloid scintigraphy; LCA shows hot lesions. On FDG PET-CT, lymphoma shows marked FDG avidity (SUVmax >5-8), LCA shows low-moderate uptake.
Distinguishing Feature
Hemangioma shows marked T2 hyperintensity ('light bulb sign'), LCA shows T2 hypointensity due to hemosiderin. Sulfur colloid: hemangioma cold, LCA hot. Hemangioma usually solitary, LCA multiple.
Distinguishing Feature
Metastasis presents as multiple lesions with known malignancy, rim enhancement + necrosis. LCA becomes isodense on delayed phase. Sulfur colloid: metastasis cold, LCA hot.
Distinguishing Feature
Sarcoidosis creates multiple small nodules but does not show as marked T2 hypointensity as LCA (no hemosiderin). Bilateral hilar LAP and pulmonary involvement accompany. ACE may be elevated.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
specialist-referralLCA is generally benign but definitive diagnosis cannot be made by imaging — histopathological and immunohistochemical examination after splenectomy is required. CD31(+)/CD68(+)/CD8(+) triple positivity is diagnostic. Splenectomy is both diagnostic and therapeutic and recurrence has not been reported. Due to association with visceral organ malignancies (20-30% of cases), comprehensive malignancy screening is recommended. Hematologic evaluation is needed for thrombocytopenia and anemia.
Littoral cell angioma is generally benign, but rare cases of malignant transformation (littoral cell angiosarcoma) have been reported. Association with other organ malignancies is debated. Splenectomy provides definitive diagnosis and treatment.