FELINE VASCULAR NEOPLASIA: MORPHOLOGIC AND IMMUNOHISTOCHEMICAL EVALUATION OF TWO, VISCERAL AND CUTANEOUS, HEMANGIOSARCOMAS

Hemangiosarcoma (HSA) is a malignant neoplasm arising from vascular endothelial cells; it is uncommon in cats, with a reported incidence of 0.3% up to 2.0%. Feline hemangiosarcoma is commonly classified as dermal or visceral, with no distinction made between cutaneous and subcutaneous origins for dermal tumors. The aim of this work is to characterize, morphologically and immunohistochemically, two cases of feline hemangiosarcoma. The first case was a female, 12 years old, DSH cat that presented a subcutaneous, expansive, ulcerated and hemorrhagic neoplasm, in the interscapular region. Cytology of the nodule was scantly cellular, with severe hemodilution; there were rare individually arranged spindle cells, with finely vacuolated cytoplasm, characterized by severe anisocytosis and anisokaryosis, elevate N/C ratio and numerous nucleoli. Grossly, adjacently to the primary neoplasm, there were numerous local metastases and lungs were characterized by myriads of metastatic nodules. The second case was a female, 11 years old, DSH cat that presented numerous, variably in size, splenic nodules. Grossly, metastatic nodules in liver and lungs were evident. Histologically, in both cases, all the primary and metastatic nodules were characterized by unencapsulated, variably infiltrative and expansile neoplasm composed of blood-filled, variably-sized and shaped, lacunae lined by endothelial neoplastic cells; multifocally there were more dense areas of spindle cells, arranged in short interlacing bundles and streams, with scant fibrovascular stroma. There were also, large and diffuse areas of necrosis and hemorrhage, surrounded by numerous hemosiderin-laden macrophages. Particularly, cutaneous hemangiosarcoma had prevalence of densely cellular pattern, meanwhile the visceral form was more lacunar, characterized by viable neoplastic endothelial rim. In both cases, pulmonary metastases were characteristically centered on bronchial blood vessels. Spleen, liver and lung also presented numerous areas of extramedullary hematopoiesis. Immunohistochemistry has been performed on primary neoplasms, local and distant metastases using factor VIII–related antigen, CD31(PECAM-1) and CD34; neoplastic nodules resulted positive for all three markers, with a more specific and homogeneous expression of CD31.