A 57-year-old male, current smoker presented with a three-year history of a right neck mass progressively enlarging. Computed Tomography Angiography (CTA) established the diagnosis of a Shamblin II carotid body tumor (CBT) 2.5×3.0cm in size. An inactive pheochromocytoma was also depicted in the left adrenal gland, 1cm in size. The internal carotid artery (ICA) was partially engaged in the tumor at 140o along its circumference while the external carotid artery (ECA) at 245o. A perivascular hypodense rim was apparent (Figure 1). The patient underwent surgical excision of the CBT with partial clamping of the ECA to aid haemostasis (Figure 2). Postoperative course was uneventful, and the patient was discharged on the 3rd postoperative day.

The presence of a perivascular hypodense rim in our patient indicates safe tumor resectability without need for ICA reconstruction or ECA excision. It corresponds to the fat plane normally lying around the arteries. Loss of this avascular plane indicates infiltration of the vessel wall by the tumor, making subadventitial dissection impossible. In a recent series from Jasper et al, the absence of this rim displayed as loss of tumor adventitia interface was significantly different between the Shamblin groups (33.3% in Shamblin I, 60% in II and 95,2% in III)1. Consequently, lack of this radiological sign increases the likelihood for tumor adherence to ICA needing arterial reconstruction and higher morbidity is anticipated (e.g., strokes and cranial nerve palsies).