Real-time elastography of parotid gland masses: the value of strain ratio for the differentiation of benign from malignant tumors

Transcription

1 Realtime elastography of parotid gland masses: the value of strain ratio for the differentiation of benign from malignant tumors Poster No.: C09 Congress: ECR 05 Type: Scientific Exhibit Authors: M. M. Coman, G. Baciut, M. T. A. Buzan, C. BotarJid, D. Vasilescu, L. M. Lenghel, S. M. Dudea ; CAMPIA TURZII, CL/ RO, ClujNapoca/RO Keywords: Tissue characterisation, Neoplasia, Diagnostic procedure, Ultrasound, Elastography, Salivary glands, Head and neck DOI: 0.594/ecr05/C09 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page of 6

2 Aims and objectives Salivary gland tumors are uncommon, constituting 6% of the tumors of the head and neck region. The most frequent location is represented by the parotid gland (up to 85% of cases) []. Preoperative tumor evaluation, including the differentiation between benign and malignant parotid gland lesions, is very important, allowing a more precise planning of the surgical intervention, thus improving the patient's outcome and decreasing the risk of facial nerve injury []. Ultrasonography is usually the first imaging technique applied due to it's advantages: noninvasiveness, nonirradiating, low cost, good resolution for superficial tissues. Realtime sonoelastography (RTE) is a relatively new qualitative method that estimates the tissue elasticity by measuring its deformation under compression [,3]. The aim of the study was to determine the value of tissuetolesion strain ratio (SR) and elastographic score (ES) for differentiating benign from malignant parotid gland tumors. Methods and materials From September 0 to May 04, 38 consecutive patients with parotid gland masses were included in a prospective study and investigated using ultrasonography in the Ultrasound Department of the County Emergency Hospital from ClujNapoca, Romania. Of these patients, 9 (50%) were women and 9 (50%) were men. The mean age was 56.7, ranging from to 87 years old. Approval for this study was obtained from the local Human Medical Research Ethics Committee Board and all subjects provided written informed consent. All the lesions included in the study underwent surgical resection or biopsy. The histopathologic diagnoses were used as the "gold standard". All patients underwent conventional ultrasonography and realtime sonoelastography using a highend ultrasound scanner equipped with a 73 MHz broadband linear transducer. Exclusion criteria included: lesions larger than 3 cm in diameter without surrounding adequate normal parotid tissue; diffuse heterogeneous parotid gland parenchyma; and lesions with macrocalcifications or with an important cystic component. For the elastogram acquisition and evaluation, freehand compressions were applied for at least 0 seconds. Only images with a quality factor of 3 or 4 as displayed on the specific scale of the scanner were recorded. Probe stabilizer was not used. The elastographic window was set as large as possible, trying to encompass as much surrounding tissue as possible. All lesions were scored on colourscaled elastograms in terms of their stiffness relative to adjacent normal salivary parenchyma, using the 4grade scoring system, from ES (soft) to ES 4 (stiff) (Table, applied by Dumitriu et al. in [4]). Parotid tissue Page of 6

3 tolesion strain ratio (SR) was acquired in all the cases, by placing the two regions of interest (ROI) boxes in the lesion, and respectively on the surrounding normal glandular parenchyma. Strain ratio was obtained by comparing the lesion with the surrounding normal parenchyma. Table. Elastographic scoring system for focal salivary gland masses Score Sonoelastographic Pattern Mass has an entirely elastic pattern, with a mixture of red, yellow and green areas. (Fig ) 3 Mass is predominantly soft compared with the surrounding normal parenchyma, with some areas of stiffness present, representing <50% of tumor area. (Fig ) 4 Mass is mostly stiff, but areas of elasticity are still present, stiffness representing >50% of tumor area (mosaic of green, yellow and blue, but mostly blue). (Fig 3) Mass is entirely stiff, with almost entirely blue areas. (Fig 4) Page 3 of 6

4 Fig. : 74yearold woman with basal cell adenoma of parotid gland which appears entirely soft (red, yellow and green) (ES ). References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO Fig. : 36yearold woman with pleomorphic adenoma of parotid, predominantly soft on the color elastogram, with some stiff (blue) areas (ES ). References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO Page 4 of 6

5 Fig. 3: 45yearold woman with acinic cell carcinoma of the parotid gland; color elastogram shows a mixed pattern in which stiff (blue) areas represent more than 50% of tumor (ES 3). References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO Page 5 of 6

6 Fig. 4: 7yearold man with pleomorphic adenoma of the parotid, which is almost entirely stiff (ES 4) References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO Statistical Analysis All data were analyzed using R statistical software version.5. (R Foundation for Statistical Computing, Vienna, Austria). Qualitative variables were compared by Fisher exact test. Differences among ES and SR for benign and malignant masses were assessed by Wilcoxon rank sum test. All probability values were sided, with a level of significance of <0.05. Images for this section: Fig. : 74yearold woman with basal cell adenoma of parotid gland which appears entirely soft (red, yellow and green) (ES ). Page 6 of 6

7 Fig. : 36yearold woman with pleomorphic adenoma of parotid, predominantly soft on the color elastogram, with some stiff (blue) areas (ES ). Fig. 3: 45yearold woman with acinic cell carcinoma of the parotid gland; color elastogram shows a mixed pattern in which stiff (blue) areas represent more than 50% of tumor (ES 3). Page 7 of 6

8 Fig. 4: 7yearold man with pleomorphic adenoma of the parotid, which is almost entirely stiff (ES 4) Page 8 of 6

9 Results The histopathological diagnoses of the 38 tumors included in this study are shown in Table. Table. Histological diagnosis of the 38 parotid gland lesions. Tumor type Number (%) Pleomorphic adenoma 6 (4.) (3.5) Whartin tumor 3 (7.8) Other benign tumors (0.0) Lymphoepitelial cyst (0.0) Epidermoid cyst (0.0) Basal cell adenoma 7 (8.4) Malignant tumors 3 (7.8) Squamous cell carcinoma (5.) Lymphoma (0.0) Acinic cell carcinoma (0.0) Metastasis (salivary duct carcinoma) Page 9 of 6

10 Fig. 6: 58yearold man with pleomorphic adenoma of the parotid gland (ES, SR= 0.9) References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO In the examined group, the cutoff was set between ES and ES 3, meaning that score of two or lower indicated a soft appearence, more probably found in the bening lesions, while scores 3 and 4 indicated a stiff appearence, indicating a possible malignant character of the lesion. ES and ES were found in benign and 4 malignant tumors, while ES 3 and ES 4 were found in 9 benign and 3 malignant tumors (Table 3). Table 3. Elastography score (ES) of the parotid gland tumors Histopathologic Number of lesions according to elastographic scoring system Diagnosis (ES) ES ES ES 3 ES Lymphoepitelial cyst Pleomorphic adenoma Whartin tumor Page 0 of 6

11 Epidermoid cyst Squamous cell carcinoma Basal adenoma cell Lymphoma Acinic cell carcinoma Metastasis (salivary duct carcinoma) Fig. 9: 87yearold man with metastasis from salivary duct carcinoma (ES 3, SR=6.65) References: Ultrasound Department, County Emergency Hospital ClujNapoca/RO The sensitivity, specificity, positive predicting value (PPV) and negative predicting value (NPV) of the strain ratio and elastographic scoring system were calculated, with a confidence interval of 95%. The diagnosis indicators are presented in Table 4. Table 4. Diagnostic indices between strain ratio and elastography score system Page of 6

12 Methods Sensitivity Elastographic 43% scoring system Strain ratio 57% Specificity PPV NPV 7% 5% 85% 84% 44% 90% Using a cutoff value of 3 for SR, 4 malignant and 6 benign tumors were true positive, indicating malignancy with a sensitivity of 57% and specificity of 84%. Using the Fisher exact test, a significant statistical difference was found between benign and malignant lesions (p=0.04) for SR, having a median[iqr] of [0.5] and 4[6,5], respectively. In the present study, the Fisher exact test revealed no statistically significant difference for the elastographic scores of the benign versus malignant lesions (p=0.65). Using the Wilcoxon rank sum test the p value for the difference between SR and ES was 0.0, Spearman test (r=0.35) showing a low linear correlation between the to diagnostic indices. Images for this section: Fig. 5: 74yearold woman with basal cell adenoma of the parotid gland (ES, SR= 0.99) Page of 6

13 Fig. 6: 58yearold man with pleomorphic adenoma of the parotid gland (ES, SR= 0.9) Fig. 7: 48yearold woman with Warthin tumor of parotid (ES, SR=0.5) Page 3 of 6

14 Fig. 8: 59yearold man with squamous cell carcinoma of the parotid gland (ES, SR=3.7) Fig. 9: 87yearold man with metastasis from salivary duct carcinoma (ES 3, SR=6.65) Page 4 of 6

15 Conclusion Some studies concluded that neither the internal structure, nor the vascularization or sonoelastographic features can identify pathology for certain and could not be used for differentiating between benign and malignant tumors. Regarding real time elastography, the most common benign parotid lesions present stiff areas [5]. Other studies presented practical aspects and potential pitfalls of the approach in the diagnosis of the salivary gland lesions and concluded that the potential role of the RTE techinque for parotid tumors is unclear and insufficient for ruling out malignancy [6,7]. Limitations of the current study are represented by the reduced number of patients, and especially of malignant lesions, due to limited feasibility: the stiffness of the lesions, its dimensions (>3 cm diameter), the lack of surrounding normal salivary parenchyma for the validity of parotid tissuetolesion strain ratio, or the less accessible location. Also, another limitation is that both ES and SR are semiquantitative methods, which does not provide such an objective comparison between different types of tumors as a quantitative estimation of elasticity would. In conclusion, the present study sugests that ES and SR have a limited sensibility in the differentiation of benign and malignant parotid gland tumors. However, SR is by comparison a better parameter for the exclusion of malignancy in lesions of the parotid gland. Personal information References. Pinkston JA, Cole P. Incidence rates of salivary gland tumors: results from a populationbased study. Otolaryngol Head Neck Surg. 999;0: Dumitriu D, Dudea SM, BotarJid C, Baciut G. Ultrasonographic and sonoelastographic features of pleomorphic adenomas of the salivary glands. Med Ultrason 00; : Bhatia KS, Rasalkar DD, Lee YP et al. Evaluation of realtime qualitative sonoelastography of focal lesions in the parotid and submandibular glands: applications and limitations. Eur Radiol 00; 0: Dumitriu D, Dudea SM, BotarJid C et al. Realtime sonoelastography of major salivary gland tumors. AJR Am J Roentgenol 0; 97:W94W930. Page 5 of 6

16 5. Klintworth N, Mantsopoulos K, Zenk J, et al Sonoelastography of parotid gland tumours: initial experience and identification of characteristic patterns. Eur Radiol 0; (5): Hasan Y, Erkan E, Ekrem K et al. Sonoelastographic qualitative analysis for management of salivary Gland Masses. J Ultrasound Med 0; 3: Bhatia KS, Cho CC, Tong CS et al (0) Shear wave elastography of focal salivary gland lesions: preliminary experience in a routine head and neck US clinic. Eur Radiol (5): Page 6 of 6