are rare. However, when a tumour extends to the submandibular, sublingual and the minor salivary glands, they tend to be malignant. Distinguishing a malignant lesion from a benign one may be difficult as they both present as painless lesions. A biopsy is crucial in aiding diagnosis. There are common signs that can highlight the presence of a malignant lesion. These include facial nerve weakness, rapid increase of the size of the lump as well as ulceration of the mucosa of the skin. Mucoepidermoid carcinoma is a common malignant tumour of the salivary glands and has a low incidence of 4–13%. Adenoid cystic carcinoma is also a common malignant salivary gland lesion and has an incidence of 4–8%. This carcinoma tends to invade nerves and can re-occur post-treatment. Polycystic Parotid Disease A developmental polycystic disease of the salivary gland is seen to be extremely rare and is seen to be independent of recurrent parotitis. The cause is thought to be a defect in the interactions between activin, follistatin and TGF-β, leading to a developmental disorder of glandular tissue. Clinical significance Parotitis Inflammation of one or both parotid glands is known as parotitis. The most common cause of parotitis is mumps. Widespread vaccination against mumps has markedly reduced the incidence of mumps parotitis. The pain of mumps is due to the swelling of the gland within its fibrous capsule. Apart from viral infection, other infections, such as bacterial, can cause parotitis (acute suppurative parotitis or chronic parotitis). These infections may cause blockage of the duct by salivary duct calculi or external compression. Parotid gland swellings can also be due to benign lymphoepithelial lesions caused by Mikulicz disease and Sjögren syndrome. Swelling of the parotid gland may also indicate the eating disorder bulimia nervosa, creating the look of a heavy jaw line. With the inflammation of mumps or obstruction of the ducts, increased levels of the salivary alpha amylase secreted by the parotid gland can be detected in the blood stream. Fibrous reactions Tuberculosis and syphilis can cause granuloma formation in the parotid glands. Salivary stones Salivary stones mainly occur within the main confluence of the ducts and within the main parotid duct. The patient usually complains of intense pain when salivating and tends to avoid foods which produce this symptom. In addition, the parotid gland may become enlarged upon trying to eat. The pain can be reproduced in clinic by squirting lemon