A thrombosed varicose vein arising in the neck is quite rare. A 68-year-old Japanese male was referred to our hospital because of a mass in his left upper neck. The mass did not change in size in response to strain resulting from Valsalva’s manouvre. Magnetic resonance imaging (MRI) showed iso-signal intensity of the mass on T1-weighted images and a target-like signal arrangement (concentric hyper-, hypo-, hyper-signal intensity from outside to inside) on T2-weighted images. Surgical excision revealed that the tumour arose from the intramuscular small vein in the sternocleidomastoid muscle. The pathological examination revealed the mass to be a thrombosed varicose vein with capillarization in the dilated vein wall. The de-oxygenation and degradation of haemoglobin were thought to be responsible for these characteristic MRI findings. The concentric signal distribution on MRI strongly suggested this pathology.
