CD81 and soft tissue neoplasm: In contrast to neuroblastic tumors, soft tissue tumors and other extraosseous sarcomas—n = 20 (18%), with 19/20 infiltrated by MFC—had a common CD56++ CD271++ CD81++ phenotype in the absence of CD45, CD34, and EpCAM expression, with three distinct (heterogeneous) phenotypic profiles (Figure 3 and Table S2).