KRAS and undifferentiated pleomorphic sarcoma: In this context, it is noteworthy that a study of UPS tumours in Korean patients identified a high frequency of oncogenic KRAS and HRAS mutations [6], but a study by the same authors of UPS tumours in American patients revealed that these tumours lacked KRAS and HRAS mutations [7], arguing that different human genetic backgrounds (or environmental factors) may select for different oncogenic mutations during the course of sarcoma development.