Experimental murine model of primary high grade undifferentiated pleomorphic sarcoma not otherwise specified.

BACKGROUND Undifferentiated pleomorphic sarcoma not otherwise specified (NOS) is a malignant neoplasm of uncertain origin arising both in the soft tissue and the bone. The WHO classified this tumour in 2002 but controversy has plagued this entity due to limited availability of tissue for study. The aim of this study was to establish a reproducible xenograft model of primary human undifferentiated pleomorphic sarcoma NOS. MATERIALS AND METHODS Primary human sarcoma samples were divided into tumour fragments and transplanted subcutaneously in mice. Sarcoma xenografts were analysed histolomorphologically (light/electron-microscopy; immunohistochemistry). RESULTS All tumours resulted in viable sarcoma NOS xenografts demonstrating similar histological patterns. In both the original tumours and the xenografts, tumour necrosis was found ranging from 15% to 25%. The background stroma of the xenografts was hyalinised like the primary sarcoma. Electron microscopical analyses showed good maintenance of ultrastructure. CONCLUSION Implantation of intact tumor fragments yielded in a complete tumor take rate. The development of new cancer therapeutics requires animal models that closely resemble the human patient. This study provides ideal animal models for the research of pathogenesis and pathobiology of primary human undifferentiated pleomorphic sarcoma NOS.