Cystic lymphangioma is a rare congenital anomaly of the lymphatic system. Its embryopathogenesis is still controversial. Most lesions present in infancy or early childhood with a swelling found in the head and neck region. We report the case of a woman who presented with a cystic swelling in the left supraclavicular region that appeared after left side thyroidectomy. Surgical excision achieved complete removal. Histology showed the lesion to be a cystic lymphangioma. It can be hypothesized that an embryogenetic origin of the adult lymphangioma is associated with some precipitating trauma such as surgery.