Section 3 -

Splenic Angiomatoid Nodular Transformation (SANT) and Lymphangioma Anthony S.Y. Leong University of Newcastle Newcastle, Australia

Presentation: A 60-year-old man presented with pain in the left upper abdomen and splenomegaly and was clinically diagnosed with metastatic tumor in the spleen. The 205g, 650 x 550 x 870mm spleen contained a relatively well defined 40 x 40 x 40mm mass, composed of rounded nodules of varying sizes with the appearance and colour of splenic tissue, encircled by grey fibrous septae. A separate 10mm subcapsular excrescence of small cystic spaces was found away from the main tumor mass. Microscopically, the nodules were confluent and of varying sizes composed of concentric spindle cells and collagen (Figs 1 & 2) with lymphocytes, macrophages, plasma cells and siderophages interspersed between the collagen (Fig 3). There were randomly placed slit-like, oval and irregular branching vascular spaces lined by somewhat prominent endothelial cells within these nodules (Figs 4 & 5). The angiomatoid nodules were formed of concentric layers of SMA positive myogenic cells with a lining of fragmented basal lamina of irregular thickness similar to that of smooth muscle cells. The endothelial cells were consistently positive for CD31 but showed variable staining for CD34 and less frequently for CD8. There was no mitotic activity and nuclear atypia was not a feature of the lesion. The separate subcapsular excrescence of cystic spaces was a lymphangioma filled with pale fluid and lined by plump endothelial cells (Fig 6). Diagnosis: Spleen (205g) – splenic angiomatoid nodular transformation (SANT) and lymphangioma Discussion This entity is sufficiently distinctively both at macroscopic and microscopic level to earn the name of 'sclerosing angiomatoid nodular transformation' (SANT). [1] In their report of 25 cases, Martel et al [1] considered these lesions to be benign vascular processes apparently unique to the spleen. The nodules are composed of vessels that replicate those in the normal splenic red pulp as recognised by their phenotype capillaries being CD34+/CD8-/CD31+, sinusoids CD34-/CD8+/CD31+ and veins CD34-/CD8-/CD31+. A recent case report has included positivity for CD68, not shown in the earlier paper. [2] Similar lesions have previously been reported under the rubric of 'multinodular hemangioma[3], splenic hamartoma, [4] and splenic hemangioendothelioma. [4] The differential diagnosis of SANT includes hemangioma and littoral angioma but these lesions are composed of single rather than multiple types of blood vessels and lack the distinctive morphological features of SANT both grossly and microscopically. Splenic hemangiomas are composed of conventional blood vessels of the CD34+/CD31+, CD8- phenotype. Littoral cell angioma was said to be composed of vascular channels lined by littoral cells or sinusoidal lining cells of the CD34-/CD8+/CD31+ phenotype and of separate nodules with a prominent pseudopapillary growth pattern and absence of sclerosis. Although an earlier report suggested that CD8+ was a feature of littoral cell angioma, [5] this has not been confirmed subsequently, [6, 7] and CD8 staining has been seen only in splenic hamartoma and some angiosarcomas. [7, 8] Sclerosing angiomatous nodular transformation of the spleen is a benign lesion of unknown histogenesis. References: Martel M, Cheuk W, Lombardi L, et al. Sclerosing angiomatoid nodular transformation (SANT): report of 25 cases of a distinctive benign splenic lesion. Am J Surg Pathol 2004;28:1268-79. Li L, Fisher DA, Stanek AE. Sclerosing angiomatoid nodular transformation (SANT) of the spleen: addition of a case with focal CD68 staining and distinctive CT features Am J Surg Pathol 2005;29:839-40 Rosai J. Rosai and Ackerman's Surgical Pathology. 9th Edition. Edinburgh: Mosby, 2004:2035. Silverman ML, LiVolsi VA. Splenic hamartoma. Am J Clin Pathol 1978;70:224-9. Kaw YT, Duwaji MS, Knisley RE, et al. Hemangioendothelioma of the spleen. Arch Pathol Lab Med 1992;116:1079-82 Rosso R, Chan JKC. Further evidence supporting the sinus lining cell nature of splenic littoral cell angiosarcoma Am J Surg Pathol 1996;20:1531. Ben-Izhak O, Bejar J, Ben-Eliezer S, Vlodavsky E. Splenic littoral cell hemangioendothelioma: a new low-grade variant of malignant littoral cell tumour Histopathology 2001;39:469-75. Arber DA, Strickler JG, Chen Y-Y, Weiss LM. Splenic vascular tumors: a histologic, immunophenotypic and virologic study. Am J Surg Pathol 1997;21:827-35.