The Curious Case of Fibrofatty Conversion of Cystic Hygroma Treated with Bleomycin Sclerotherapy

Cystic hygroma is a congenital malformation of the lymphatic system that mostly presents at birth. Though the classic treatment of this condition is surgical excision, recent alternative treatment modalities such as injection of sclerotherapeutic agents (e.g., bleomycin and OK-432) into the lesion has gained popularity due to its safe and effective response profile with minimal side effects. We report a rare complication of repeated bleomycin sclerotherapy in a follow-up patient of cystic hygroma, where the lesion underwent fibrolipomatous conversion with insinuation into multiple fascial planes, causing mass effect by encasement and compression of major vascular and airway structures. This is the first time such a complication of bleomycin sclerotherapy has been reported in literature. Such an unusual presentation reminds us that, in any patient presenting with recurrent gradually increasing swelling with worsening of symptoms following bleomycin sclerotherapy, a possibility of fibrolipomatous conversion of cystic hygroma should be borne in mind.