CD34 and head and neck squamous cell carcinoma: Taken together the data suggest either (1) the CD34 hematopoietic stem cells derived from mobilized adult HNSCC are capable of engraftment and differentiation to T cells, or (2) that rare mature T cells contaminating the CD34+ cells selected from the mobilized apheresis product expanded slowly in the mice over the 30 weeks without causing xeno-GvHD for more than 6 months.