WHEN EMBRYOLOGY SPEAKS: A CYST’S LONG SILENCE FINALLY BROKEN horaciosousa98@gmail.com

PE040

WHEN EMBRYOLOGY SPEAKS: A CYST’S LONG SILENCE FINALLY BROKEN

7

Portugal

Poster Exhibition only

Branchial cleft cysts are congenital malformations from persistence of branchial apparatus remnants, most frequently involving the second cleft. They typically present as slow-growing, mobile, painless, well-circumscribed lateral neck masses. While common in pediatric populations, they may also occur in adults, where the differential diagnosis is broader.

A 47-year-old woman with hypothyroidism on levothyroxine presented with a right paramedian cervical swelling of 18 months’ duration. She reported progressive enlargement after weight loss, with increased visibility and discomfort but no compressive symptoms. Physical examination revealed a soft, mobile, painless mass measuring ~6 × 3 cm, located anterior to the right sternocleidomastoid muscle. Contrast-enhanced cervical CT showed a well-defined, hypodense lesion (32 × 25 mm) posterior to the right submandibular gland, without enhancement, consistent with a second branchial cleft cyst. Ultrasound-guided fine-needle aspiration cytology was negative for malignancy and showed benign content.

Complete surgical excision was performed without complications. The postoperative course was uneventful, with no recurrence on follow-up. In adults, lateral cervical masses should prompt consideration of second branchial cleft cysts alongside infectious or neoplastic lymphadenopathy, dermoid cysts, lipomas, paragangliomas, and salivary gland lesions. Characteristic location, absence of systemic symptoms, and imaging features guide diagnosis. CT provides detailed anatomical assessment, and cytology excludes malignancy. Definitive treatment is surgical excision, with low recurrence rates when performed outside inflammatory episodes.

This case underscores the need to include second branchial cleft cysts in the differential diagnosis of adult lateral neck masses. Combined clinical, imaging, and cytological evaluation enables accurate diagnosis and safe planning, ensuring outcomes.