POU5F1 and vascular neoplasm: The elevated IHC scores observed for malignant and borderline vascular tumors correlated to the results obtained in a diverse panel of malignant sarcoma cells, revealing immunoreactivity for Oct4, Nanog, and Sox2 in 100 % of various sarcoma tissues and 72 % for Myc and Kfl4 (Additional file 2: Table S2).