We report a case of spontaneous resolution of a recurrent axillary cystic hygroma in a 4-year-old boy. He presented with a 1-year history of a cystic lump in the left axilla, which intermittently changed in size. Ultrasound suggested it was a lipoma, with raised suspicions of vascular malformation. Scans were discussed in a multidisciplinary meeting and provisional diagnosis of lymphocele or slow flow lymphovascular malformation was made. It was surgically excised and histology confirmed the lesion to be a cystic hygroma. However, it recurred within 3 weeks. The patient was booked for aspiration and treatment with sclerotic agent OK 432. He developed acute infection in the cystic hygroma a week before surgical intervention and was treated with antibiotics for 5 days by his general practitioner. Acute infection led to complete spontaneous resolution of the cystic hygroma within a week. There are no other reported cases in which recurrent cystic hygroma has resolved after a week of acute infection.

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