One of the Largest Reported Ciliated Foregut Cysts of the Gallbladder Mimicking a Gallbladder Diverticulum.

Ciliated foregut cysts are rare congenital lesions derived from abnormal budding of the primitive foregut and are most commonly identified in the mediastinum or liver, where they may also be referred to as bronchogenic-type cysts. Occurrence within the gallbladder is extremely uncommon, with only a limited number of cases reported in the literature. We present the case of a 29-year-old male who presented with right upper quadrant abdominal pain, nausea, and vomiting. Computed tomography and ultrasound revealed a cystic lesion adjacent to the gallbladder that was initially interpreted radiologically as a probable gallbladder diverticulum. The patient subsequently underwent laparoscopic cholecystectomy. Gross examination demonstrated a 3.5 cm subserosal cystic lesion within the gallbladder wall. Histologic evaluation revealed a cyst lined by pseudostratified ciliated columnar (respiratory-type) epithelium with mucinous differentiation, consistent with a ciliated foregut cyst. No dysplasia or malignancy was identified. The patient's postoperative course was uncomplicated. Ciliated foregut cysts of the gallbladder may mimic gallbladder diverticula or other cystic lesions on imaging, making preoperative diagnosis challenging. The cyst in the present case measured 3.5 cm and represents one of the largest reported ciliated foregut cysts of the gallbladder in the literature. This case highlights the importance of histopathologic evaluation and the need to consider a ciliated foregut cyst in the differential diagnosis of cystic lesions associated with the gallbladder.