RB1 and soft tissue neoplasm: The loss of 13q14 especially in the RB1 gene is also common in other soft tissue tumors (e.g., cellular angiofibroma or myofibroblastoma of the breast), which together with the overlapping morphology and IHC (loss of RB1 and CD34 positivity) supports the hypothesis of a spectrum of genetically related 13q/RB1 family tumors.