Fig. 4.
Undifferentiated stromal sarcoma (high-grade, fibroblastic reticular), spleen, dog, case 2. (a) Neoplasm composed of a uniform population of streaming bundles of polygonal to spindle-shaped mesenchymal cells with indistinct cell borders, mild to moderate anisokaryosis and a high mitotic rate. HE. (b) Neoplastic spindle cells immunonegative for desmin. IHC. (c) CD204 labelling in a minority of individualized cells throughout neoplasm, interpreted as remnant histiocytes or infiltrating tumour-associated macrophages. IHC. (d) Neoplastic spindle cells have uniformly strong cytoplasmic immunolabelling of PDPN. IHC.