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.

Abstract

BACKGROUND: There has been a lack of research regarding diagnostic immunohistochemistry in soft tissue pathology in rodents. OBJECTIVES: We aimed to analyse the immunohistochemical expression of CD34, keratin AE1/AE3, keratin 8/18, desmin, KIT, SMA, S100, and vimentin in various malignant mesenchymal tumours in guinea pigs. METHODS: A total of 62 tumours included 10 fibrosarcomas, 8 myxosarcomas, 8 undifferentiated pleomorphic sarcomas, 6 undifferentiated round cell sarcomas, 6 dedifferentiated liposarcomas (involving deep soft tissue, skin or subcutis), 12 uterine leiomyosarcomas, 4 hemangiosarcomas (involving skin and spleen), and 8 gastrointestinal stromal tumours (GIST). RESULTS: Desmin and SMA positivity was present in tumours of various lineages, including hemangiosarcoma. CD34 positivity was restricted to hemangiosarcomas, GISTs and one case of undifferentiated pleomorphic sarcoma, whereas KIT positivity was detected only in GISTs. Lesser amounts of keratins positivity were observed in fibrosarcoma, myxosarcoma, undifferentiated pleomorphic sarcoma, and dedifferentiated liposarcoma. S100 positivity was identified in myxosarcoma, undifferentiated pleomorphic sarcoma, and dediffentiated liposarcoma and vimentin positivity was detected in all tumour types. CONCLUSIONS: 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.