Spontaneous rupture of spleen: histological, immunohistochemical and ultrastructural study.

Pathological examination in the spleen of an 81-year old female with hemoperitoneum, hypovolemic shock, anemia, thrombocytopenia and hyperglicemia revealed the presence of an angiosarcoma. On histological examination, characteristically the neoplasm was formed by vascular lumina and cystic spaces into which papillary fronds projected and solid nests. Neoplastic cells had scant cytoplasm, hyperchromatic, oval or reniform nuclei, with prominent nucleoli. The necrosis was evident and mitoses were frequent. Immunohistochemical analysis revealed positivity for endothelial (CD31, CD34) and histiocytic markers (CD68 and lysozyme) and negativity for CD21. Ultrastructural examination also disclosed a biphasic differentiation, showing the presence of organelles associated with histiocytic and endothelial differentiation. These findings suggest that this lesion can be considered a conventional splenic angiosarcoma with focal histocytic differentiation.