A vascular spindle cell lesion abuts the splenic capsule (top left). Extravasated red cells percolate within the lesion.

Neoplastic endothelial cells proliferate and form vascular channels. The lesion is rather cellular and brings to mind Kaposi's sarcoma.

The endothelial cells exhibit some pleomorphism. But hemangioendotheliomas are not as cellular or pleomorphic as angiosarcomas.

Splenic tumors that are of the non-lymphoid variety are usually vascular. Examples of vascular tumors include hemangioma, littoral cell angioma (a variant of hemangioma), hemangioendothelioma, and angiosarcoma. Hemangioma is the most common benign tumor of the spleen. Most hemangiomas are cavernous. The neoplastic endothelial cells are positive for Factor VIII-releated antigen, CD31 and CD34.

Hemangioendotheliomas lie between hemangiomas and angiosarcomas in terms of clinicopathologic features. They are not as bland as hemangiomas and are much more cellular with anastamosing channels. They are considered of intermediate/borderline malignancy.

Symptoms are usually nonspecific, such as localized abdominal pain. Some patients have hypersplenism.