Cystic hygroma reconsidered: hamartoma or neoplasm? Primary culture of an endothelial cell line from a massive cervicomediastinal hygroma with bony lymphangiomatosis.

A young woman presented with massive enlargement of a giant cervicomediastinal cystic hygroma, which communicated in part with the thoracic duct and was associated with generalized bony lymphangiomatosis. Modern imaging and sophisticated intraoperative physiologic monitoring made one-stage resection feasible. Tissue culture of explants of the hygroma yielded a primary endothelial cell line still surviving after 18 months, which, like the cyst-lining endothelium in the original resected specimen, reacted positively for Factor VIII-associated antigen. These findings, in conjunction with the histologic picture, support the notion that cystic hygroma represents an expanding proliferating endothelial growth process and not simply a sequestered lymphatic receptacle.