This 28 year old female presented with a 2 year history of a small gradually enlarging lump on the right side of her neck. There were no associated pressure symptoms or discharge. On examination a non-tender, mobile and fluctuant lump was noted at the anterior border of her right sterno mastoid muscle. There was no associated lymphadenopathy.
The mass was surgically excised and is an ovoid cyst 6 cm in maximum dimension. The outer surface of the cyst shows a fine vascular pattern together with fibroadipose adhesions. The cyst originally contained turbid dark yellow material whilst the inner lining shows a fine nodularity, individual nodules measuring up to 3 mm in maximum diameter. Histologically the cyst is lined by a layer of stratified squamous epithelium external to which are collections of lymphocytes, some of which include germinal centres.