Myoid angioendothelioma of the spleen.

Although vascular neoplasms of the spleen are rare, they are the most common nonhemopoietic proliferation of the organ, and include hemangiomas, lymphangiomas, hamartomas, littoral cell angiomas, hemangioendotheliomas, and angiosarcomas, as well as the recently described myoid angioendothelioma (MA). MA is an uncommon, benign tumor of the spleen, which is morphologically characterized by a composite of vascular spaces and stromal cells with myoid features. In 1999, in the only report of this unusual neoplasm, Kraus and Dehner described the features of 3 cases. We present another case of MA of the spleen occurring in a 51-year-old man that demonstrated the characteristic morphologic and immunohistochemical features of this neoplasm. In addition to the features described by Kraus and Dehner, our case also displayed the previously unreported findings of focal spindling of the stromal cells and scattered S100-positive cells in the stroma. The case was further unique in having a central stellate scar. Careful attention to histology, possibly with the aid of immunohistochemistry, should distinguish other splenic neoplasms from MA. Although MA is a morphologically distinct lesion, its histologic spectrum, biological behavior, and relationship to other vascular tumors are yet to be fully discovered. It is hoped that the recognition of further cases, and the use of newer molecular technologies, will help better define the nosological position and implications of the diagnosis of this unusual tumor.