Delayed enhancement in differential diagnosis of salivary gland neoplasm

Abstract

Background: Multi-phasic Computed Tomography (CT) evaluation allows to study the enhancement features of parotid gland masses. The aim of our study was to evaluate the role of delayed enhancement in the characterization of different histologic types of parotid tumours.

Methods: Forty-eight patients (22 male and 26 female) with at least one parotid gland tumor, were included in our study. Multi-phase CT images were obtained before and 30, 120 s and 8 minutes after intravenous contrast injection. The images were evaluated by two radiologists for lesion enhancement degree. A quantitative assessment was performed using a region of interest on each lesion and density changes between different phases were compared. The tumoral enhancement ratio was calculated between the 8 minutes delayed and the early (30 s) phase. The pathological diagnosis was confirmed in all patients after surgery.

Results: All patients had unilateral lesion for a total of 48 lesions. Twenty-eight were pleomorphic adenomas, 15 Warthin's tumours and 5 carcinomas. All Warthin tumours showed a rapid contrast enhancement at the early phase (30 sec) followed by a progressive wash-out during the delayed scans. Most of pleomorphic adenomas (89.2%) showed the highest density at the 8-minutes delayed phase. Malignant tumours showed slower contrast enhancement and 3 out of 5 (60%) showed a marked decrease at the 8 minutes delayed phase while the remaining 2 (40%), did not show any density reduction. The tumoral enhancement ratio was significantly different between Warthin tumours and pleomorphic adenomas and between Warthin's and malignant tumours.

Conclusions: Multi-phasic CT examination with 8 minutes delayed acquisition has shown to be useful in parotid gland lesion differentiation.

Keywords: Parotid gland; computed tomography; neoplasm.

Figure 1

A 60-year-old woman with pleomorphic adenoma in the superficial lobe of the left parotid gland. (A) Axial early (30-sec) phase CT image showed a slight contrast-enhancement of the mass; (B) after 120-sec, CT scan showed an increase of tumour enhancement; (C) the delayed acquisition (after 8-min) demonstrated a continued slow increase in enhancement of the lesion.

Figure 2

Time attenuation curves of different parotid tumours. Warthin tumours showed a rapid contrast enhancement at the early phase (30 seconds) and a progressive wash-out during the delayed phases (120 s and 8 min) while pleomorphic adenomas showed an increased enhancement during the delayed phases. The majority of malignant carcinomas showed a peak enhancement at 120-sec phase and a marked decrease at the 8-minute delayed phase.