Sarcomas lacking expected pathognomonic fusions (for example, lack of NAB2-STAT6 in a solitary fibrous tumor) were noted as potential diagnostic errors and termed “sarcoma, unclassified” (n = 172), while a non-specific diagnosis of liposarcoma was further refined to well/dedifferentiated liposarcoma when MDM2 gene amplification was found. The gene discussed is NAB2; the disease is solitary fibrous tumor.