Unusually rapid development of a lateral neck mass: Diagnosis and treatment of a branchial cleft cyst. A case report.

Introduction: Branchial cleft cysts are benign lesions caused by anomalous development of the branchial cleft. Cases that arise in the lateral neck region are often misdiagnosed, resulting initially in inappropriate management.

Case presentation: We describe a 32-year-old woman with a swelling on the right side of her neck and no pain during palpation or neck motion.

Discussion: The patient was evaluated using fine-needle aspiration cytology (FNAC), ultrasound, and magnetic resonance imaging (MRI) scans. The MRI showed a right-sided cervical mass with hyperintense content, well-defined margins, and no evidence of infiltration into surrounding structures, while FNAC found a yellow, pus-like fluid, keratinised anuclear cells, squamous epithelium, and a matrix of amorphous debris.

Conclusion: Based on the images and the patient's symptoms, a surgical intervention was performed.