Dental practitioners are sometimes confronted with patients complaining about pain in the neck area. Especially if an induration in the region of the big vessels is present, one must keep in mind the differential diagnosis of a spontaneous thrombosis of the external jugular vein. This diagnosis needs consequent treatment but also consequent search for an underlying pathology. This case report presents such a situation in an exemplary way. Despite risk factors, the reason for thrombosis stays in the dark. However, all possible causes were cleared and are shown to the reader. Especially malignancies are responsible for thrombosis of the jugular vein in many cases.