Sclerosing stromal tumour in a cow

A case of sclerosing stromal tumour in an 8-year-old cow is described. The left ovary was entirely replaced by neoplastic tissue, whose features were pseudolobulation of cellular areas, intercellular oedema and calcified plaques. The neoplastic cells varied in morphology and were similar to ovarian stromal cells, theca cells or lutein cells. Immunohistochemically, S-100 protein, oestradiol and testosterone were detected in theca-like or luteinized cells, some of which had ultrastructural features suggestive of steroid hormone synthesis. In contrast, desmin and actin characterized slender spindle cells. This is the first report of a sclerosing stromal tumour in cattle.