Sclerosing angiomatoid nodular transformation of the spleen.

Sclerosing angiomatoid nodular transformation (SANT) is a recently recognized nonneoplastic vascular lesion of the spleen with fewer than 30 cases described. Microscopically, SANT consists of multiple well-circumscribed vascular/angiomatoid nodules showing plump endothelial cell and extravasated erythrocytes. The nodules are surrounded by a variable lymphoplasmacytic infiltrate, spindle cells, and collagenous stroma. The vascular nodules display a complex mixture of endothelial phenotypes resembling splenic sinusoids (CD34-/CD31+/CD8+), capillaries (CD34+/ CD31+/CD8-), and small veins (CD34-/CD31+/CD8-). Focal expression of CD68 can also be seen. The differential diagnosis of SANT includes splenic hamartoma, inflammatory myofibroblastic tumor, littoral cell angioma, and hemangioendothelioma. It has been postulated that SANT represents a peculiar hamartomatous transformation of splenic red pulp in response to an exaggerated nonneoplastic stromal proliferation. SANT has a benign clinical course with splenectomy being curative.