Diagnostic challenges and perioperative management of a lateral cystic neck mass in an adult patient with hemophilia B: A case report.

Lymphatic malformations and branchial cleft anomalies are rare congenital lesions that can present similarly as cystic neck masses, often in childhood, but occasionally in adults. Differentiating between the two can be challenging, especially when clinical, radiographic, and cytologic findings overlap. We present the case of a 41-year-old male with hemophilia B and a right lateral cystic neck mass, underscoring preoperative diagnostic ambiguity and illustrating perioperative coordination required for safe surgical excision in a patient with a bleeding disorder. On examination, patient's neck had a mobile, cystic feeling, 5 cm right upper neck mass lateral or involving the sternocleidomastoid muscle. Computed tomography imaging revealed a 5 cm cystic lesion deep to the sternocleidomastoid muscle. Ultrasound-guided fine needle aspiration showed bland lymphocytes, suggesting either a second branchial cleft cyst or macrocystic lymphatic malformation. Due to diagnostic uncertainty and the potential for future infection, the patient underwent surgical excision following perioperative Factor IX replacement. Final pathology confirmed a lymphatic malformation. This case highlights the diagnostic overlap of lateral cystic neck masses in adults and emphasizes the importance of multidisciplinary care in patients with comorbidities such as hemophilia.