Therefore, when HA-derived material is very small in size and occurs in an area where minor salivary glands are present, such as the buccal mucosa in the present case, care should be taken not to confuse it with low-grade mucoepidermoid carcinoma or other mucin-producing minor salivary gland tumours. The gene discussed is MUC5AC; the disease is mucoepidermoid carcinoma.