Sclerosing angiomatoid nodular transformation of the spleen

A 25-year-old woman with an incidental 8-cm splenic mass underwent splenectomy. Cut surface of the 280-g spleen demonstrated a sharply defined bosselated mass, in which was found multiple reddish-brown bulging nodules demarcated by dense tan fibrous tissue and central scarring (panel A). The nodules comprised vascular spaces (panels B-C, hematoxylin and eosin stain, original magnification ×100 and ×200, respectively) lined by CD31⁺ endothelial cells (panel D, original magnification ×100) in a background containing red cells and myofibroblasts that stained for smooth muscle actin and myosin (not shown). CD8 stain reveals that sinusoids present in adjacent red pulp (right) are absent from the nodules (panel E, original magnification ×200).

Sclerosing angiomatoid nodular transformation (SANT) is a benign vascular sclerosing mass-like lesion, encountered more frequently with increased use of imaging studies. Since 1994, ∼150 cases of SANT have been reported. Most are asymptomatic, but SANT may cause abdominal pain or discomfort. SANT manifests radiologically as a well-defined solid lesion, and magnetic resonance imaging characteristically reveals a wheel-and-spoke pattern of nodular enhancement. Radiologic differential diagnosis includes hemangioma, littoral cell angioma, and angiosarcoma. Desmoplastic metastatic carcinoma has also been reported to cause nodular masses in the spleen. Unlike splenic hamartoma, which similarly contain elements found in splenic red pulp, the borders of SANT are well circumscribed, and hamartomas lack the distinctive nodular angiomatoid pattern.