Immunoreactivity for CD34, Desmin, Keratins, KIT, Alpha‐Smooth Muscle Actin, S100, and Vimentin in Malignant Mesenchymal Neoplasms in Guinea Pigs: A Series of 62 Cases From a Single Institution

The strong and diffuse staining pattern of desmin and SMA can be very helpful in distinguishing leiomyosarcoma from its spindle cell mimics. A novel finding is that SMA positivity was identified in malignant endothelium. Immunolabelling for CD34 and KIT provides reliable markers for vascular neoplasms and GISTs. Vimentin does not allow to distinguish between different mesenchymal malignancies in guinea pigs. Occasional positivity for keratins and S100 points to potential pitfalls and emphasised the need for a panel of immunohistochemical stains in the investigation of mesenchymal tumours.