Neonatal teratoma presenting as hygroma colli.

We describe a neonate with a large tumour involving cranial, cervical and upper mediastinal regions, which presented clinically as hygroma colli. Radiological and pathological investigations showed characteristics of a mature teratoma and prominent cystic components within the tumour. These findings suggest that during early fetal development primary lymphatic sacs were obstructed by a teratoma leading to hygromatous dilatations of lymphatic vessels or that the abnormal proliferation of lymphatic vessels (hygroma) was part of the teratoma, developing from mesoderm as one of the three germinal layers from which teratomas originate. A third possibility is that the cystic part of the tumour originated from plexus chorioideus tissue, containing CSF. The last possibility is most probable in this patient.