Metastasizing splenic littoral cell hemangioendothelioma.

Littoral cell angioma is a unique splenic tumor that is generally considered to be benign. We present a case of a low-grade littoral cell splenic tumor that metastasized to the liver and retroperitoneum 4 years after splenectomy. Although the splenic lesion showed the typical morphology of a littoral cell angioma, it also contained areas with unusual solid nests of cytologically bland, plump cells with clear cytoplasm. The liver was diffusely infiltrated exclusively by cells with similar clear cell features. Both splenic and liver lesions demonstrated identical immunophenotypes, typical of littoral cell angioma, expressing CD31, CD68, CD21, and CD163, although negative for CD8 and CD34. A single prior description of a littoral cell hemangioendothelioma showed nuclear atypia and necrosis, and this is the first case report of a splenic littoral cell hemangioendothelioma with a completely bland histologic appearance. This case suggests that the presence of solid areas of clear cells in a littoral cell angioma may be a marker of low-grade malignant potential in these tumors.