Branchial cleft cyst.Second branchial cleft cyst branchial cleft cyst Branchial cyst A cyst-like embryologic rest–remnant present at birth, which arises from branchial clefts, usually the 2nd anomalies can occur in two forms or distributions. In infants, a mass can be found at the level of the angle of the mandible. If an associated fistulous fis·tu·lous or fis·tu·lar
Relating to or containing a fistula.
pertaining to or of the nature of a fistula. tract is present, the opening is identified in the anterior neck just above the clavicle. The second form is found in young adults. Usually trauma or infection produces the initial appearance of a cystic mass at the level of the mandible. In some cases, there is a history of "unsuccessful abscess drainage." 
Computed tomography (CT) and magnetic resonance imaging magnetic resonance imaging (MRI), noninvasive diagnostic technique that uses nuclear magnetic resonance to produce cross-sectional images of organs and other internal body structures. might reveal a unilocular unilocular /uni·loc·u·lar/ (-lok´u-ler) having but one cavity or compartment.
Having a single compartment or cavity; monolocular. cystic mass in the posterior submandibular submandibular /sub·man·dib·u·lar/ (sub?man-dib´u-ler) below the mandible.
submandibular (sub´mandib´y space at the level of the mandibular angle. As the mass enlarges, it usually displaces the submandibular gland anteromedially, the sternocleido-mastoid muscle posterolaterally, and the contents of the carotid space posteromedially (figure). The jugulodigastric lymph node is located in the same area as a typical second branchial cleft cyst. As a result, a second branchial cleft cyst can be mistaken for an enlarged suppurative suppurative
pertaining to or emanating from suppuration; pus in e.g. suppurative arthritis, bronchopneumonia. , reactive, or tumor-infiltrated jugulodigastric node. 
From the Department of Radiology, Louisiana State University Health Science Center, New Orleans (Dr. Palacios), and the Department of Radiology and Otolaryngology, University of Illinois Medical Center, Chicago (Dr. Valvassori).
(1.) Harnsberger HR. Cystic masses of the head and neck: Rare lesions with characteristic radiologic features. In: Harnsberger HR. Handbook of Head and Neck Imaging. 2nd ed. St. Louis: Mosby, 1995:199-223.