PDGFRA and spindle cell sarcoma: Paraffin-embedded sections of KSHV-infected PDGFRA-positive MSCs tumors (K-Pα(+)S KS tumor) stained with hematoxylin and eosin (H&E) were analyzed by a pathologist in a blind manner, confirming that these tumors were indistinguishable from the vascularized spindle cell sarcomas formed by mECK36 tumors previously generated by our lab, which were thoroughly characterized as KS-like tumors [26] (Fig 1G).