Third and fourth branchial cleft cysts - A 25-year institutional experience of imaging detection and pathologic diagnosis.

BACKGROUND AND PURPOSE: Third and fourth branchial cleft cysts (BCCs) are rare and often mimic other lower-neck cystic lesions. Tract conspicuity is frequently limited on single-time-point imaging, particularly during inflammation. We report a 25-year institutional experience evaluating Proportion Undergoing Surgery and Pathology-Confirmed BCC Rate.

MATERIALS AND

METHODS

We retrospectively queried radiology reports (January 2000-December 2024) to identify suspected third and fourth BCCs. Reports and images were reviewed to classify lesions; pathology was cross-referenced for operated cases. Outcomes were (1) Proportion Undergoing Surgery rate (operated/total) by modality and clinical setting and (2) Pathology-Confirmed BCC Rate (PPV for any BCC among operated) overall, by modality, and by imaging category (3rd, 4th, 3rd vs 4th). Exact (Clopper-Pearson) 95% CIs were calculated. An exploratory logistic regression among operated patients evaluated predictors of Pathology-Confirmed BCC. Analyses used IBM SPSS Statistics 27.0.

RESULTS

Fifty-two patients met inclusion criteria (US 34.6%, CT 50.0%, MR 15.4%). Distribution by setting was 73.1% outpatient, 11.5% inpatient, and 15.4% emergency department. Overall, 24/52 (46.2%) underwent surgery. Proportion Undergoing Surgery rates by modality were 44.4% (US), 46.2% (CT), 50.0% (MR). Proportion Undergoing Surgery by setting was 42.1% (outpatient), 33.3% (inpatient), 75.0% (ED). Among operated patients, pathology confirmed BCC in 5/24 (PPV 20.8%; 95% CI, 7.1-42.2). PPV by modality: 50.0% (US), 8.3% (CT), 0.0% (MR). PPV by imaging category: 9.1% (3rd), 25.0% (4th), 40.0% ("3rd vs 4th"). No covariate was a significant predictor of pathologic confirmation in exploratory modeling; some parameters were not estimatable due to sparse cells.

CONCLUSIONS

Third and fourth BCCs are rare. Fewer than half of suspected third and fourth BCCs on imaging were operated on - only a minority of these were pathologically confirmed. Imaging alone seems unlikely to be able to distinguish between third and fourth BCCs or to delineate these lesions from similar cystic abnormalities in the neck.