Littoral cell angioma of spleen: a clinicopathologic study of 17 cases

Abstract

To study the clinicopathologic features and immunophenotype of splenic littoral cell angioma. The clinical features, radiologic findings and histopathology of 17 cases of splenic littoral cell angioma were retrospectively reviewed. Immunohistochemical study was carried out on paraffin-embedded tissues, using normal spleen, cases of congestive splenomegaly and cavernous hemangioma as controls. All the 17 cases had similar clinical manifestations and radiologic findings. There was mild to moderate splenomegaly, with solitary or multifocal space-occupying lesions. Hepatic cysts were observed in 5 of the 17 cases. One case was also accompanied by serous cystadenoma of ovary. Gross examination revealed enlarged spleen containing single or multiple tan-colored nodules which ranged from 0.2 cm to 6.0 cm in diameter. Histologically, the lesions consisted of anastomosing vascular channels, sometimes with papillary or cavernous appearance. Two types of component cells were identified. A population of smaller cells lined the vascular channels, while another population of larger cells often floated in the vascular lumen. Both cell populations showed little cytologic atypia. Immunohistochemical study demonstrated that the smaller cells of all cases were positive for CD31 and polyclonal factor VIII-related antigen. They were negative for CD34, histiocytic markers and S-100 protein. CD8 and CD21 were expressed in 1 and 1 of the 17 cases respectively. On the other hand, the larger cells expressed histiocytic markers, including CD68 (KP1 and PG-M1), CD163 and lysozyme. There was also focal positivity for CD31. The staining for CD34, monocolonal factor VIII-related antigen and S-100 protein was negative. The immunophenotype of splenic littoral cell angioma was different from that of the controls. Littoral cell angioma is a benign condition, likely secondary to hemodynamic disturbance in spleen. The littoral cells become hyperplastic and anastomose, resulting in a hemangioma-like growth associated with histiocytic reaction. Attention to the characteristic histopathologic findings and immunophenotype are crucial for diagnosis.