Anaplastic and aggressive subcutaneous sarcoma in a seven-month-old dog

A seven-month-old female, Italian hound which was presented with anorexia, dyspnoea and weight loss showed two subcutaneous masses at physical examination. Radiographs showed multiple opacities in the lungs, thorax, liver and spleen, and cytology showed discrete pleomorphic cells, with variable nuclear : cytoplasmic ratio, foamy cytoplasm and round to oval nuclei. Incisional biopsy histology showed the infiltrative proliferation of highly pleomorphic spindle to roundish large cells, discrete or arranged in a storiform pattern, with scattered multinucleated giant cells. Immunohistochemistry exhibited strong positivity for vimentin and mild labelling for alpha-smooth muscle actin and lysozyme; other mesenchymal or histiocytic lineage markers stained negatively. Because of the poor prognosis, the owner elected euthanasia. Post-mortem examination confirmed massive metastatic spread. Cytology, histology and immunohistochemistry suggested the diagnosis of anaplastic sarcoma with giant cells, although disseminated histiocytic sarcoma was a reliable differential diagnosis. The authors underline the difficulties in definitively categorising poorly differentiated sarcomas, even if a large panel of markers is applied.