Pathological characterization of primary splenic myxoid liposarcomas in three dogs.

Non-angiomatous-non-lymphomatous sarcomas (NANLs) represent 23%–34% of canine primary splenic sarcomas. Splenic liposarcomas account for 2%–6% of NANLs but myxoid variants are rarely reported and information on their behaviour is fragmentary. An 8-year-old male crossbreed (case 1), a 12-year-old female French bulldog (case 2), and an 11-year-old crossbreed (case 3) underwent splenectomy after the detection of a splenic nodule. Histology, histochemistry, immunohistochemistry, and transmission electron microscopy (TEM) were performed. Bundles of spindle-to-polygonal cells containing occasional cytoplasmic oil-red-O positive vacuoles embedded in an Alcian blue-positive extracellular matrix were observed. Aggregates of round cells were detected in cases 1 and 3. All tumours were vimentin positive and actin, desmin, Factor VIII, and S100 negative. The TEM evidenced different maturational stages of adipose cells (lipoblasts, intermediate, and undifferentiated). All the cases developed hepatic metastases and were euthanized. Disease free interval was 2 months in cases 1 and 3, and 21 months in case 2. The presence of a neoplastic embolus in case 1 and areas of round cell differentiation in cases 1 and 3 represented the sole prognostic indices.