Sclerosing Angiomatoid Nodular Transformation (SANT) of spleen
This benign spleen lesion consists of a well circumscribed lesion with abundant fibrosis surrounding lobules of vascular structures. These structures resemble the normal splenic parenchyma immunohistochemically.
Due to the normal splenic parenchymal components and vascular components, this is thought by some to represent a fibrosing variant of a splenic hamartoma or a subset of hemangioma. In a series of 25 cases, 17 patients were females and 8 were males. The ages ranged from 22 to 74 years, with a mean of 48.4 years and a median of 56 years. There was no recurrent disease in any case with follow up. The specimens weighed from 68 g to 1425 g, and the lesions ranged from 3 cm to 17 cm. All of the lesions were singular, well circumscribed, nodular, fibrotic, with numerous red-brown nodules. All cases consisted of a fibrous stroma around multiple angiomatoid nodules. The angiomatoid nodules were made of round, slit-like, or irregular shaped vascular spaces lined by plump endothelial cells without atypia and very rare mitoses (less than 1 per 10 HPF). Lymphocytes and other scattered inflammatory cells were present in varying amounts. The vascular spaces were filled by red blood cells. There were scattered spindle to oval cells indistinct eosinophilic cytoplasm, and vesicular nuclei. The fibrous or fibromyxoid stoma contained bland spindle cells, scattered lymphocytes, plasma cells, and histiocytes, and areas of hyalinization. Immunohistochemically, the capillaries were CD34+, CD31+, and CD8 negative. The small veins were CD31+ and CD34 and CD8 negative. The sinusoids were CD31+ and CD8 + and CD34 negative. The lining cells were negative for CD21 and CD68. The spindle cells in the fibrous tissue were positive for smooth muscle actin.
Littoral cell hemangiomas are often multiple, nodular, spongy lesions. They are anastomosing vascular channels with papillary projections and cystic spaces. The lining cells are tall endothelial cells with no atypia which express Factor VIII, CD21, CD31, and CD68. They do not express CD8 or CD34.
Hemangiomas are the most common primary tumors of the spleen. Grossly, they are usually bloody and cystic. They resemble hemangiomas at other sites, and are often cavernous. They express Factor VIII and CD31 but lack CD8 expression.
Hamartomas are rare, well circumscribed lesions of the red pulp. They are composed of a proliferation of sinuses similar to that of the surrounding tissue. White pulp elements are not present. Unlike the dense fibrous stroma of SANT, hamartoma stroma is loose with inflammatory cells, spindle cells, and varying amounts of fibrosis. The lining cells are positive for CD8, similar to normal red pulp sinuses, as well as CD31 and Factor VIII.
Inflammatory pseudotumors are well circumscribed and usually singular. The cut surface is white or yellow. They consist of a mixture of lymphocytes, plasma cells, and possibly neutrophils and eosinophils, with areas of fibrosis containing benign-appearing spindle cells.
Martel M, Cheuk W, Lombardi L, Lifschitz-Mercer B, Chan JK, Rosai J. Sclerosing angiomatoid nodular transformation (SANT): report of 25 cases of a distinctive benign splenic lesion. Am J Surg Pathol. 2004 Oct;28(10):1268-79.
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Silverberg S, DeLellis R, Frable W, LiVolsi V, Wick M. Silverberg's Principles and Practice of Surgical Pathology and Cytopathology, 4th edition. 2006. Churchill Livingstone Elsevier.
Contributed by Aaron Berg, MD