eP-124 The Diagnostic Utility of Magnetic Resonance Imaging with Diffusion Weighted Imaging for the Differential Diagnosis of Glomus Tumors A Gunes, B Ozgen, A Dolgun, N Suslu Hacettepe University, Ankara,Turkey

Conflict of interest All authors declare no conflict of interest.

Purpose We aimed to assess the contribution of signal properties, contrast enhancement and the apparent diffusion coefficient (ADC) of glomus tumors (GT) in the neck in order to increase the diagnostic accuracy of magnetic resonance imaging (MRI) for the differential diagnosis of the GT from other benign (BT) and malignant tumors (MT) of the neck. This is the first study in the literature evaluating the GT regarding MR diffusion characteristics compared to other masses.

Materials and Methods Patients Inclusion criterias MR imaging performed between 2006 and 2015 Biopsy / surgery performed subsequently Histopathological results in our hospitals database Exclusion criterias Patients who had undergone biopsy or who had underwent treatment before MRI poor diagnostic quality or artefact on DW imaging

Materials and Methods MRI technique; All MRI examinations were performed using 1.5 Tesla devices Symphony, Siemens, Erlangen, Germany Achieva, Philips Healthcare, Netherlands GE Healthcare, Milwaukee, WI Imaging technique; Axial and coronal T1WI Fat suppressed axial and coronal T2 WI Postcontrast fat suppressed axial and coronal T1WI Single-shot echo-planar DWI

Materials and Methods Image evaluation T1 and T2 signal intensity T1WI (repetition time, 550-600 ms; echo time, 14-20 ms) T2 WI (repetition time, 4000-4200 ms; echo time, 70-80 ms) T2 signal homogeneity Contrast enhancement Postcontrast FS T1WI (repetition time, 600-620 ms; echo time, 14-18 ms) DW trace image signal properties (applied with 3 b-values with a maximum of 1000 s/mm2, repetition time, 5100 ms; echo time, 137 ms, matrix of 96–128, and 3-mm slice thickness). Apparent diffusion coefficient (ADC) values mean ADC of the entire lesion (ADC mean) the pons (ADC pons)

Materials and Methods Statistical analysis Shapiro Wilk test Mann-Whitney U test Chi-Square test, Fisher’s Exact test, or Fisher-Freeman-Halton test

Materials and Methods Total (n:99) Glomus tumors (n:38) Benign tumors (n:22) Malignant tumors (n:39) Caroticum(n:12) Peripheral nerve sheath tumors (n:12) Metastatic lymphadenopathy (n:28) Vagale (n:1) Meningioma (n:5) Lymphomas (n:4) Jugulare (n:12) Hemangioma (n:1) Squamous cell carcinoma (n:2) Tympanicum (n:2) Oncocytic adenoma (n:1) Small round cell tumors (n:4) Jugulotympanicum (n:11) Fibrous tumors (n:3) Granulocytic sarcoma (n:1)

Results There were significant differences between GT and MT in; T2 signal properties and heterogeneity MT had higher T2 intensity than GT (p=0.005) GT more heterogenous on T2 WI than MT(p<0.001). contrast enhancement GT more intense gadolinium enhancement than MT (p<0.001)

Results There were significant differences between GT and MT in; DWI signal properties MT more hyperintense than GT (p=0.001) the mean ADC values mean ADC values of GT >> MT (p=0.012) The ADC tumor / ADC pons ratios of GT > MT (p= 0.011) For diagnosing GT the mean ADC value has 94.9% sensitivity 57.9% specificity 0.76 accuracy (with an ADC cut-off value of ≥1.08)

Results ADC mean Malignant tumors 0,88±0,14x10-3 mm2/s Glomus tumors Benign tumors 1,28±0,32x10-3 mm2/s

Ax post Gd FS T1WI Ax FS T2WI DWI Sag SE T1WI ADC map 48-year-old woman with carotid body tumor demonstrating heterogeneous tumor in the right carotid space, with heterogeneously enhancement and restricted diffusion. The mean ADC is 1.14x10-3 mm2/s. Sag SE T1WI ADC map

Ax FS T2WI Ax post Gd FS T1WI DWI Cor post Gd FS T1WI ADC map 54-year-old woman with glomus vagale tumor demonstrating heterogeneous tumor in the right jugulare space, with heterogeneously enhancement .The tumor shows no diffusion restriction. The mean ADC is 1.48x10-3 mm2/s. Cor post Gd FS T1WI ADC map

Ax T2WI Ax post Gd T1WI DWI Cor post Gd T1WI ADC map 36-year-old man with glomus jugulare tumor showing heterogeneous tumor in the left jugulare space, with heterogeneously enhancement. The mean ADC is 0.90x10-3 mm2/s. Cor post Gd T1WI ADC map

Ax T2WI Ax post Gd T1WI DWI ADC map Cor post Gd FS T1WI 64-year-old woman with glomus jugulotympanicum tumor demonstrating heterogeneous intensity of tumor in the left jugulotympanicum, with heterogeneously enhancement. The mean ADC is 1.63x10-3 mm2/s. ADC map Cor post Gd FS T1WI

Ax post Gd FS T1WI Ax FS T2WI DWI Cor post Gd FS T1WI ADC map 59-year-old man with squamous cell carcinoma tumor demonstrating heterogeneous tumor in the right mastoid and jugulare foramen, with heterogeneously enhancement. The mean ADC is 0.96x10-3 mm2/s. Cor post Gd FS T1WI ADC map

Ax post Gd FS T1WI Ax FS T2WI DWI Cor post Gd FS T1WI ADC map 55-year-old man with metastatic lymphadenopathy secondary to squamous cell carcinoma demonstrating homogeneous enhancement. The mean ADC is 0.84x10-3 mm2/s. Cor post Gd FS T1WI ADC map

Ax post Gd FS T1WI Ax FS T2WI DWI Cor FS T2WI ADC map 41-year-old woman with meningioma showing similar signal intensity to brain parenchyma on T2WI, with heterogeneously enhancement. The mean ADC is 0.86x10-3 mm2/s. Cor FS T2WI ADC map

Ax post Gd FS T1WI Ax FS T2WI DWI Cor post Gd FS T1WI ADC map 38-year-old woman with schwannoma tumor demonstrating heterogeneous high signal intensity of mass in the right carotid space, with heterogeneously enhancement. The mean ADC is 1.09x10-3 mm2/s. Cor post Gd FS T1WI ADC map

Discussion Glomus tumors (non-chromaffin paraganglioma) non-capsulated hypervascular slowly growing tumors of neural crest origin a diagnostic biopsy is not performed for definite diagnosis of GT because of their tendency to bleed the diagnosis is usually a presumptive one based on imaging the main diagnostic modalities for GT are CT and MRI the most prominent feature of GT hypervascularity as reflected by serpentine or punctuate signal void areas on MRI (the salt and pepper appearance) early contrast uptake on contrast enhanced dynamic CT and MR angiography.

Discussion The salt and pepper appearance on MRI is not pathognomonic for GT. This imaging appearance may also be seen in schwannomas, vascular tumors or metastatic lesions The reason why GT showed lower signal intensity than MT might be the drop of T2 signal secondary to internal heterogeneity and flow-voids in GT

Discussion The heterogeneity on T2WI and the different enhancement degree of the tumors result from the different histopathological patterns of lesions GT are composed of nests of cells with characteristic cellular Zellballen pattern separated by numerous vascular channels within a fibrous matrix. Tumor cells contain a hyperchromatic nucleus and chromatin in a dispersed pattern; this histopathological property may explain the mean ADC values of GT (1.06±0.55x10-3mm2/s) falling between those of benign and malignant tumors

Conclusion ADC ratios, T2 and DW signal properties as well as contrast enhancement of the neck masses on MRI are helpful for the differential diagnosis of glomus tumors from malignant tumors.

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