RB1 and soft tissue neoplasm: This article will provide a contemporary review on the histopathologic and clinical features of this group of soft tissue tumors with RB1 loss (spindle cell and pleomorphic lipoma, atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, myofibroblastoma, cellular angiofibroma, acral fibromyxoma) and their differential diagnoses.