An occult case of the first branchial cleft anomaly.

We report a case of the first branchial cleft anomaly, clinically typical but occult in images and pathology. An 8-year-old female who had an induration below her right mandibular angle was referred to our department with a diagnosis of an infectious epidermal cyst. CT and MRI had shown no evidence of fistula or cyst. At the initial operation, a string structure was observed, but pathologically no epithelial structure was observed. However, the infection at the same site repeated and the symptoms became more severe than before. Considering a high probability of the first branchial anomaly, partial parotidectomy was performed as radical surgery. A cord structure attached to subcutaneous tissue at the intertragal notch was found. Although no epithelial component in the pathology was detected, this string structure was clinically considered as the rudimentary form of the first branchial anomaly.