Arteriovenous malformation with hair collar sign.

We report the case of a newborn who was noted at birth to have an occipital scalp nodule presenting with a hair collar sign (HCS). The nodule had enlarged since birth. An MRI revealed a soft tissue mass on the occipital scalp without deep extension or cranial bone involvement. A biopsy of the nodule led to a diagnosis of arteriovenous malformation (AVM). A vascular malformation with HCS has not been reported before in North America. This case highlights the complexity of diagnosing a lesion with a hair collar sign.