The definition of branchial cysts, sinuses and fistulae.

In a study of 57 lateral cervical lesions, 46 cysts were found to form a homogeneous group and four sinuses and fistulae formed another homogeneous group. The cysts lay behind the angle of the mandible, and were lined by stratified squamous epithelium resting on lymphoid tissue, with part of the wall resembling a lymph node. The sinuses and fistulae had life-long external openings and were muscular tubes lined by respiratory-type epithelium. The other seven lesions had some other structure. Such uniformity of clinico-pathological features of supposed branchial lesions has not been demonstrated before and no explicit definition of them has ever been published. We suggest that our empirical findings in the two groups of lesions can be used as clinico-pathological definitions of "branchial cysts' and "brachial sinuses and fistula' respectively. Lesions with other features should be given other names.