Splenic hemangioendothelioma is a rare low-to-intermediate grade vascular neoplasm of the spleen. It arises from endothelial cells and occupies a biological spectrum between benign hemangioma and high-grade angiosarcoma. Epithelioid hemangioendothelioma (EHE) is the most common subtype. Clinical behavior is variable — some cases show slow growth while others may demonstrate locally aggressive behavior. Metastatic potential exists but is significantly lower than angiosarcoma. On imaging, it appears as a heterogeneously enhancing solid mass or nodules. Significant hemorrhage and necrosis are less than in angiosarcoma. Splenectomy may be curative and prognosis is much better than angiosarcoma (5-year survival 50-80%).
Age Range
30-70
Peak Age
50
Gender
Equal
Prevalence
Rare
Hemangioendothelioma is a low-to-intermediate grade neoplasm arising from vascular endothelial cells, positioned between benign hemangioma and malignant angiosarcoma. Tumor cells express endothelial markers (CD31, CD34, ERG) and form primitive vascular channels but cannot form mature, well-organized vascular structures. In epithelioid hemangioendothelioma, WWTR1-CAMTA1 fusion gene (90%) or YAP1-TFE3 fusion gene (10%) is the diagnostic genetic anomaly. Tumor cells are embedded in myxoid or hyalinized stroma with a tendency to form vascular lumina. This low-to-intermediate grade vascular architecture produces a slow-progressive enhancement pattern on imaging — different from angiosarcoma's aggressive hypervascularity. Intratumoral hemorrhage is possible but not at the massive, spontaneous rupture-inducing level seen in angiosarcoma. Tumor margins are better defined and capsular infiltration is less common. The sclerotic/hyalinized component reflects as low density on CT and low T2 signal on MRI.
Heterogeneous signal on MR T2 with characteristic hyalinized stroma hypointense areas and progressive but incomplete enhancement on delayed phase — the combined finding that positions hemangioendothelioma in the vascular tumor spectrum. This pattern differs from both hemangioma's complete fill-in with high T2 signal and angiosarcoma's hemorrhagic-necrotic T2 pattern.
In the arterial phase, the tumor shows moderate heterogeneous enhancement. Enhancement is less prominent than angiosarcoma's intense hypervascular pattern. Solid components enhance mildly hypodense or isodense to splenic parenchyma. Mass margins are relatively well-defined. Significant necrotic or hemorrhagic areas are less extensive than in angiosarcoma.
Report Sentence
Moderate heterogeneous enhancement of the splenic mass is observed in the arterial phase; intense hypervascularity is absent; consistent with a low-to-intermediate grade vascular neoplasm.
In the delayed phase, progressive contrast accumulation is seen in the vascular components of the tumor, but hyalinized/sclerotic stroma areas remain hypodense. This pattern differs from benign hemangioma's complete fill-in pattern — in hemangioendothelioma, complete fill-in does not occur due to hyalinized stroma. In the late phase, enhancement equilibrium develops and heterogeneity decreases but does not disappear.
Report Sentence
Progressive enhancement in the splenic mass on delayed phase but hyalinized stroma areas remain hypodense; complete fill-in does not occur; consistent with hemangioendothelioma.
On T1-weighted sequences, the tumor shows isointense-to-mildly hypointense signal relative to splenic parenchyma. If intratumoral hemorrhage areas are present, T1 hyperintense foci (methemoglobin) may be seen but this finding is not as extensive as in angiosarcoma. Hyalinized stroma shows low signal on T1.
Report Sentence
The splenic mass shows isointense-to-mildly hypointense signal on T1-weighted sequences; no significant intratumoral hemorrhage is observed.
On T2-weighted sequences, the tumor shows heterogeneous signal. Vascular components have intermediate-to-high T2 signal. Hyalinized/sclerotic stroma areas are markedly T2 hypointense — this low-signal component is a distinguishing feature of hemangioendothelioma. The bright T2 signal expected in hemangioma is not fully present in hemangioendothelioma. Mixed signal pattern (intermediate + low) is characteristic.
Report Sentence
The splenic mass shows heterogeneous signal on T2-weighted sequences containing markedly hypointense areas corresponding to hyalinized stroma component; consistent with hemangioendothelioma.
On DWI, mild-to-moderate diffusion restriction may be observed in the solid tumor components (ADC: 1.0-1.4 × 10⁻³ mm²/s). Restriction is less pronounced than in angiosarcoma (angiosarcoma ADC: <1.0). Hyalinized stroma areas do not show diffusion restriction due to low water content.
Report Sentence
Mild-to-moderate diffusion restriction in the solid components of the splenic mass on DWI, consistent with a low-to-intermediate grade vascular neoplasm.
On B-mode US, a heterogeneous echogenicity solid mass is seen in the splenic parenchyma. Mass margins are relatively well-defined. Internal structure is solid-dominant with mixed echogenicity. Cystic component or significant hemorrhage is not as dominant as in angiosarcoma. Moderate vascularity is observed on Doppler examination.
Report Sentence
A relatively well-defined, heterogeneous echogenicity solid mass is observed in the splenic parenchyma on B-mode US; hemangioendothelioma should be considered in the differential diagnosis.
Criteria
Most common subtype. WWTR1-CAMTA1 or YAP1-TFE3 fusion gene is diagnostic. Epithelioid endothelial cells embedded in myxoid/hyalinized stroma.
Distinct Features
Multiorgan involvement possible (liver, lung, bone). Hyalinized stroma creates prominent T2 hypointensity on MR. Slower course than angiosarcoma but metastatic potential exists.
Criteria
More commonly seen in children. Kasabach-Merritt phenomenon (consumptive coagulopathy) may accompany. Shows aggressive local growth.
Distinct Features
More common in pediatric age group. Thrombocytopenia and coagulopathy (Kasabach-Merritt) are diagnostic clues. Radiologically more homogeneous and vascular appearance.
Criteria
Very rare, low-grade subtype. Shows retiform (net-like) vascular pattern. High local recurrence rate but metastasis is rare.
Distinct Features
More common in superficial soft tissues, very rare in spleen. Net-like vascular architecture is pathologically diagnostic. Prognosis is better than other subtypes.
Distinguishing Feature
Angiosarcoma is high-grade, aggressive, with extensive necrosis-hemorrhage (T1 hyperintensity), spontaneous rupture risk, and poor prognosis. Hemangioendothelioma is lower-grade, more organized, with hyalinized stroma T2 hypointensity dominant, limited hemorrhage, and better prognosis.
Distinguishing Feature
In hemangioma, peripheral nodular enhancement + complete centripetal fill-in + homogeneous high T2 signal is typical. In hemangioendothelioma, fill-in is incomplete (hyalinized stroma does not fill), T2 signal is mixed, and enhancement is more heterogeneous.
Distinguishing Feature
Littoral cell angioma is a spleen-specific benign vascular neoplasm. Presents as multiple small nodules. T2 isointense-to-mildly hypointense, T1 isointense. Hemangioendothelioma usually presents as single or few masses with hyalinized stroma creating prominent T2 hypointensity.
Distinguishing Feature
Lymphoma forms hypovascular, homogeneously enhancing nodules; no vascular tumor enhancement pattern. Hemangioendothelioma shows progressive enhancement as a vascular neoplasm. B symptoms and lymphadenopathy accompany lymphoma.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
6-monthSplenic hemangioendothelioma is a low-to-intermediate grade vascular neoplasm where splenectomy may be curative. Post-surgical 5-year survival is 50-80% — much better prognosis than angiosarcoma. Biopsy (usually via splenectomy) is needed for histopathological diagnosis and grading. In multiorgan EHE, systemic therapy (chemotherapy, immunotherapy, tyrosine kinase inhibitors) is considered. Post-surgical CT/MR follow-up at 6-month intervals is recommended (recurrence and metastasis screening). Multidisciplinary oncology and pathology evaluation is mandatory.
Splenic hemangioendothelioma has low-to-intermediate malignant potential. Splenectomy serves both diagnostic and therapeutic purposes. Long-term follow-up is required as late recurrence and metastasis have been reported.