Choose Top of page <<ReferencesCITING ARTICLES

A 36-year-old woman presented with 2 weeks of worsening left upper quadrant abdominal pain. CT revealed a 7.5-cm solid, well-circumscribed mass arising from the inferior aspect of the spleen. Compared with normal splenic tissue, on unenhanced images the mass was minimally lower in attenuation and hypoattenuating during hepatic arterial and portal venous phases but showed undulating enhancement at the periphery (Figs. 1A, 1B, 1C, and 1D). On delayed images obtained 3 minutes after contrast injection, the mass was nearly isodense with normal spleen, with the exception of an unenhanced central stellate area. The mass did not show enhancement characteristics that have been described for more common benign solid splenic masses, such as hemangioma (peripheral enhancement followed by hyperattenuation) or hamartoma (early heterogeneous to uniform delayed hyperattenuation) [1]. The gross specimen showed multiple red–brown nodules with a prominent central stellate scar (Fig. 1E). Microscopically, the mass contained multiple angiomatoid nodules within fibrous stroma and vascular slit-like spaces, consistent with the diagnosis of sclerosing angiomatoid nodular transformation (SANT) (Fig. 1F).

SANT is a benign vascular splenic mass, which has been reported in less than 30 cases [2–5]. Reported cases have shown a ratio of 2:1 for women to men and a mean age of 48 years (age range, 22–74 years). The size ranges from 3 to 17 cm in diameter [3]. Half of the patients were asymptomatic, and SANT was discovered incidentally. In the other half, abdominal pain or discomfort, splenomegaly, or pancytopenia was the initial presenting condition [3]. The pathogenesis of SANT is unknown, and a strong correlation with another disease process has not been found [3, 4].

SANT has a distinctive gross appearance. It is a well-circumscribed mass composed of numerous nodules derived from red pulp alternating with bands of dense fibrous tissue that coalesce to form a central, stellate fibrous scar [3]. Microscopically, SANT is characterized by multiple nodular aggregates of plump endothelial cells and pericytes lining prominent slitlike vascular spaces [2–5]. The nodules are associated with extravasated erythrocytes, and the intervening collagenous stroma contains variable numbers of reactive myofibroblasts, hemosiderin-laden macrophages, lymphocytes, and plasma cells. The endothelial cells exhibit minimal cytologic atypia, with rare mitotic activity [2–5].

Limited imaging information is conveyed by the pathology literature. Two articles provide correlative enhanced CT images [4, 5]. Both have images or descriptions depicting a hypodense mass in the early portal venous phase, with areas of peripheral enhancement that become homogeneous on more delayed imaging. Description of MR findings in one case indicates that the mass showed low signal on T1 and T2 sequences [4]. A recent report, however, describes a single case showing early peripheral enhancement progressing centripetally in a radial pattern [6].

Although the small number of cases with radiologic description precludes definitive assessment, suggestive characteristics of SANT include a well-circumscribed solitary mass of the spleen that initially shows low attenuation with areas of peripheral enhancement after the administration of contrast material. This may reflect the gross pathologic appearance of central fibrous stroma and more peripheral coalescent nodules of angiomatoid tissue. Additionally, the central fibrous scar was readily apparent on 3-minute delayed images (Fig. 1D).

View larger version (159K)

Fig. 1A —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Unenhanced axial CT image shows large, solid, well-circumscribed mass within inferior splenic parenchyma. Attenuation of mass is only slightly lower than that of spleen.

View larger version (169K)

Fig. 1B —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Axial contrast-enhanced CT image in early hepatic arterial phase shows mass is predominantly hypodense in comparison with splenic parenchyma, with areas of peripheral enhancement.

View larger version (166K)

Fig. 1C —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Axial contrast-enhanced CT image in portal venous phase shows heterogeneous enhancement of splenic mass, which still remains hypodense to splenic parenchyma.

View larger version (171K)

Fig. 1D —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Axial contrast-enhanced CT image obtained at 3-minute delay shows mass is nearly isodense, with exception of central stellate area of lower attenuation.

View larger version (122K)

Fig. 1E —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Photograph of gross pathologic specimen shows solitary unencapsulated but well-circumscribed mass with multiple red–brown nodules separated by stellate fibrous stroma. Arrow indicates adjacent rim of normal spleen.

View larger version (139K)

Fig. 1F —36-year-old woman with sclerosing angiomatoid nodular transformation (SANT) of the spleen. Low-power photomicrograph shows coalescing angiomatoid nodules (arrows) embedded in dense fibrous stroma. Vascular proliferation is composed of slitlike irregular-shaped vascular spaces (H and E, ×200). Inset high-power photomicrograph shows vascular spaces are lined with plump endothelial cells (arrow) exhibiting minimal cytologic atypia (H and E, ×400).