CHL1 and gastrointestinal stromal tumor: Systemic CHL1 levels were significantly elevated in GIST patients (n = 102, median 11.6 ng/ml, standard deviation (SD) ±4.7 ng/ml) compared to healthy controls (n = 76, mean 8.5 ng/ml, SD ±5.1 ng/ml, p = 0.001; Figure 4A).