Atypical Imaging Appearances of First Branchial Cleft Anomalies: Two Pathologically Proven First Branchial Cleft Anomalies Containing Fat on Imaging

Branchial anomalies (BA) are developmental lesions that are believed to be either vestigial remnants resulting from incomplete obliteration of the branchial apparatus or the result of buried epithelial cell rests. They are classifi ed as either fi rst, second, third, or fourth according to their proposed pouch or cleft of origin and are relatively common fi ndings. The incidence of BAs depends on the age of the patient and the specifi c type of anomaly. Some anomalies might be very small and not present until they become symptomatic from an inciting event such as infection or trauma. Most radiologists are familiar with the classic fi ndings of the most common forms of 1st and 2nd BAs. However, some BAs can have a varied imaging appearance and may be misdiagnosed. In this paper, we present two cases of pathologically proven fi rst branchial cleft anomalies with atypical imaging appearances.


Introduction
Branchial anomalies (BA) are developmental lesions that are believed to be either vestigial remnants resulting from incomplete obliteration of the branchial apparatus or the result of buried epithelial cell rests. They are classifi ed as either fi rst, second, third, or fourth according to their proposed pouch or cleft of origin and are relatively common fi ndings. The incidence of BAs depends on the age of the patient and the specifi c type of anomaly. Some anomalies might be very small and not present until they become symptomatic from an inciting event such as infection or trauma. Most radiologists are familiar with the classic fi ndings of the most common forms of 1 st and 2 nd BAs. However, some BAs can have a varied imaging appearance and may be misdiagnosed. In this paper, we present two cases of pathologically proven fi rst branchial cleft anomalies with atypical imaging appearances.

Case 1
A 24 year old male patient presents to the clinic with a right parotid mass. Contrast enhanced head and neck MRI was performed which demonstrated a fat containing lesion in the right parotid gland. The mass was surgically resected and sent to pathology. Pathology confi rmed the mass to be a branchial cleft anomaly (Figure 1a,b).

Case 2
A 10 year old girl presents to the clinic with a left parotid mass. Ultrasound over the area of concern demonstrated an echogenic mass in the left parotid gland. A contrast enhanced CT scan was then performed which demonstrated a fat containing mass in the left parotid gland. The mass was surgically resected and sent to pathology. Pathology confi rmed the mass to a branchial cleft anomaly (Figure 2a

Discussion
In this paper, we present parotid masses in two different patients that on CT, MRI and US contained areas of fat. The cases are part of a larger retrospective review study of the branchial cleft anomalies we had performed to determine the diagnostic accuracy of properly diagnosing branchial anomalies. Prior to performing the study, institutional review board approval was obtained. The pathology database was queried for a list of pathologically proven branchial anomalies (BA) for adult and pediatric patients that had undergone surgical excision of a neck mass between 1/1985 and 12/2012. These studies were cross-referenced with imaging to determine which pathologically proven cases had correlative imaging. All of the imaging studies and reports were then retrospectively reviewed and the branchial cleft anomalies were classifi ed based on the branchial arch origin by a board certifi ed, fellowship trained neuroradiologist.
During this retrospective review, we came across several branchial cleft anomalies with atypical imaging fi ndings. Two of those cases were described in this paper. Histologically, the diagnosis of a branchial anomaly was determined by the  branchial cleft anomaly from other cystic mass of the parotid gland ( Figure 3). If there is involvement of the deep lobe of the parotid gland, then it may extend into the adjacent fatcontaining parapharyngeal space [5].
Parotid masses can be benign and malignant. Differential diagnosis for some benign mass like presentations include fi rst branchial cleft anomaly, epidermoid cyst, dermoid, lymphoepithelial cyst, abscess, Warthin's tumor and pleomorphic adenoma. Differential for malignant parotid masses include mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma, carcinoma ex-pleomorphic adenoma, squamous cell carcinoma and adenocarcinoma.

Conclusion
This case report illustrates how branchial cleft anomalies can sometimes present with atypical imaging fi ndings and therefore it is important to include these in the differential in the appropriate clinical setting.