BackgroundLymphatic malformations (LMs) in the mediastinum are uncommon. However, cervical LMs may expand into the mediastinum. The aim of this study was to review our experience with the management of patients with LMs involving the mediastinum and to propose a treatment algorithm to guide the management of these rare malformations. Material and MethodsThis was a descriptive retrospective chart review of all patients with LMs involving the mediastinum treated at our Institution between 2009 and 2015. We collected demographic data, data on investigations, management, and complications of the treatment, as well as outcomes at follow-up. Complications were defined and described according to the Clavien-Dindo classification. The clinical outcome was assessed using a clinical assessment scale. ResultsThe cohort consisted of seven patients. Airway compromise at the time of diagnosis was seen in 4 patients. Three patients had anatomical compression of the trachea and two patients had sub-total compression of the right lung. All three patients with tracheoscopy-verified compression of the trachea had compromise of the distal trachea, and a tracheostomy would not have been protective. All patients received sclerotherapy. The median time with mechanical ventilation at the neonatal intensive care unit after each sclerotherapy was eleven days (range 8–31). Each patient received sclerotherapy in median three times (range 1–9). Five of the patients (71%) were operated with excision of the LM in the mediastinum. Two of the patients were operated primarily and three patients were operated after major complications to sclerotherapy. The patients treated with sclerotherapy and the operated patients had comparable amount of mild complications, Clavien-Dindo grade I-II complications. Severe complications, Clavien-Dindo grade III-IV, were seen five times more commonly after sclerotherapy than after surgery. The clinical outcome was excellent for the operated patients and fair to good for the patients receiving only sclerotherapy. ConclusionPatients with cervical LM involving the mediastinum represent a high-risk group with respect to the severity of complications following sclerotherapy. The swelling is unpredictable and requires extended observation at an intensive care unit with ventilation support. Tracheostomy does not prevent tracheal compression in mediastinal LM, as the malformation may compress trachea distal to the stoma. Surgical resection of the LM in the mediastinum is recommended, with the possibility of intra-operative sclerotherapy as an adjunctive. Level of EvidenceIV.