MUC5AC and cancer: PMEC belongs to the salivary-gland type of lung malignant neoplasms and arises from the salivary gland-type epithelium of the central airway.[5] Histologically, PMEC consists of epithelioid cells (or squamoid cells), mucin-secreting cells, and intermediate cells (or transitional cells) that are divided into high-grade and low-grade variants.