In contrast with previous studies, our findings did not support the concept that CgA values were higher in well-differentiated NET than in poorly differentiated tumors.21 Interestingly, we found that serum CgA levels of patients with poorly differentiated tumors which were classified as NEC + MANEC, were much higher than well-differentiated NET patients (106 ng/ml vs. 51 ng/ml, P = 0.035). Here, CGA is linked to neuroendocrine carcinoma.