P2.240: Mediastinal Cystic Lymphangioma mimicking Asthma in a child with chronic recurrent respiratory symptoms: A Case report

Introduction: Cystic lymphangiomas are rare benign lesions arising from fetal life sequestration of lymphatic vessels in an abnormal pattern. They are most often located in neck and axilla with < 1% seen in the mediastinum. They are often incidental and asymptomatic until complications from mass effect.

Case Description: We present herein the case of a 5-year-old child former 30 weeker with Chiari malformation, status post VP shunt, scoliosis, mild pulmonary stenosis and chronic intermittent respiratory symptoms of cough, dyspnea and “wheezing” mimicking asthma. Whole exome sequencing done showed 3 variants of uncertain significance in the NF1 gene. However, he did not meet criteria for the diagnosis of NF1 per geneticist and they recommended clinical follow up and possible WES re-analysis in future. His “Asthma” remained uncontrolled despite high dose inhaled corticosteroid. Therefore, he underwent CT chest with contrast that revealed a 5.9 cm cystic mass in the anterior mediastinum adjacent to the main pulmonary artery and left pulmonary vein without any obvious mass effect on airway or vascular structures. He underwent thoracoscopic excision of the mass. Intraoperatively, the cyst was adherent to the left phrenic nerve and small portion of the mass surrounding the nerve was left unresected to preserve diaphragmatic function. Histopathological examination of the excised mass showed a cystic lesion lined by CD31, Fli-1, and D2-40 positive endothelial cells, thereby confirming cystic lymphangioma. The patient recovered uneventfully in the postoperative period without any complication. Follow-up diaphragmatic ultrasound done 5 weeks post-surgery showed normal diaphragm excursions. His asthma-like symptoms have significantly resolved with no recurrence of symptoms despite weaning inhaled corticosteroid from high dose to low dose.

Discussion: Mediastinal lymphangiomas are rare, benign tumours of the lymphatic system, often asymptomatic and incidentally detected. Compression-induced symptoms include dyspnea or dysphagia due to mass effect. Diagnosis is made with CT/MRI and biopsy. Optimal treatment is by surgical excision; complete resection decreases recurrence, and sclerotherapy is an alternative option in unresectable cases. In this case, the presentation mimicking asthma and the patient's complex medical history led to a delay in diagnosis. The phrenic nerve was spared by partial excision, balancing recurrence risk against morbidity and is in accordance with evidence for minimal recurrence with incomplete resection given its benign characteristics.

Conclusion: This case illustrates the diagnostic challenge of Mediastinal cystic lymphangiomas, which are asymptomatic until causing mass effect. Our case highlights atypical presentation mimicking asthma. Imaging helps to establish diagnosis, but histopathology is definitive. The definitive treatment is surgery with minimal risk of recurrence. This case highlights the importance of considering lymphatic malformations in the differential diagnosis of mediastinal masses, particularly in children with chronic respiratory symptoms refractory to medical treatment.