Median numbers and ranges of circulating CD34+ cells were 2.3 × 106/L (0–5) in control subjects, 2.2 × 106/L (0–14) in those with PV, 2.4 × 106/L (0–14) in those with ET, and 114 × 106/L (6–2520) in PMF patients [25]. Here, CD34 is linked to essential thrombocythemia.