MUC5AC and thyroid gland carcinoma: FCGBP is the Fc fragment connexin of immunoglobulin G. Recent studies have demonstrated that FCGBP has a similar mucin-like structure, and its expression is reduced in many solid tumours such as gallbladder cancer [43], thyroid cancer [44], and colon cancer [45], suggesting that it is associated with tumour incidence and progression.