MUC5AC and basal cell carcinoma: The mucin is diastase and hyaluronidase resistant sialidase labile, thus making it nonsulfated sialomucin and distinguishable from hyaluronidase‐sensitive sulfomucin from other sweat gland tumors, basal cell carcinoma, lacrimal gland tumors, and metastatic mucinous adenocarcinoma of the gastrointestinal tract.