Frozen section during parotid surgery revisited: efficacy of its applications and changing trend of indications

Correlation between MRI (DWI and DCE) and cellularity of parotid gland pleomorphic adenomas

PURPOSE

Parotid pleomorphic adenomas present a risk of recurrence, higher when the tumour is a hypocellular subtype. The aim of the study was to determine whether it is possible to characterize this histological subtype with diffusion and perfusion sequences of the preoperative MRI.

METHODS

This retrospective study included 97 patients operated between 2010 and 2020. Histologic slides review was performed to classify tumours into three histologic subtypes: hypocellular, classical and hypercellular. Univariate and multivariate analyses studied the correlation between histology and diffusion and perfusion MRI parameters obtained with OleaSphere® software.

RESULTS

The hypocellular subtype had higher apparent diffusion coefficient values than the other two subtypes: 2.13 ± 0.23, 1.83 ± 0.42, and 1.61 ± 0.4 × 10-3 mm2/s for hypocellular, classical and hypercellular subtype respectively (p < 0.0001). Multivariate analysis showed that an ADCmean > 1.88 × 10-3 mm2/s was suggestive of a hypocellular pleomorphic adenoma in 79% of the cases, with a specificity and PPV of 94 and 96% (p < 0.001), respectively.

CONCLUSION

The histological subtype of a pleomorphic adenoma can be predicted preoperatively with ADC values. A prospective and multicentric study on a larger cohort is needed to confirm our results.

Fine-Needle Aspiration Cytology for Parotid Tumors

Fine-needle aspiration (FNA) cytology is widely used in clinical practice as a simple and minimally invasive test for parotid tumors that allows for preoperative estimation of benignancy and malignancy, histological type, and malignancy grade and can be performed on an outpatient basis. In recent years, cell blocks prepared with core needle biopsy (CNB) and liquid-based cytology (LBC) have increased the reliability of immunostaining and molecular biological testing, leading to improved diagnostic accuracy. In 2018, the Milan System for Reporting Salivary Gland Cytology was introduced, but it does not include malignancy grade or histological type, so we proposed the Osaka Medical College classification as a more clinically based cell classification that includes both types of information, and we have reported on its usefulness. This review gives an overview of the history and use of FNA and describes CNB and LBC and the two classification systems.

Current Salivary Glands Biopsy Techniques: A Comprehensive Review

Biopsy is a surgical procedure performed to collect a portion of tissue or organ for diagnostic studies. The aim of the present manuscript is to describe state-of-the-art major and minor salivary gland biopsy techniques and assess the indications and complications of other salivary gland biopsy techniques. A search was performed using the following MeSH terms: biopsy, fine-needle biopsies, image-guided biopsies, frozen sections, and salivary glands disease. A current overview of major and minor salivary glands biopsy techniques was provided. In the oncological field, a comparison was made between the most widely used biopsy method, ultrasound-guided fine-needle aspiration biopsy (US-FNAB), and an alternative method, ultrasound-guided core needle biopsy (US-guided CNB), highlighting the advantages and disadvantages of each. Finally, intra-operative frozen sections (IOFSs) were presented as an additional intraoperative diagnostic method. Minor salivary gland biopsy (MSGB) is the simplest diagnostic method used by clinicians in the diagnosis of inflammatory and autoimmune diseases. In neoplastic lesions, US-FNAB represents the most performed method; however, due to its low diagnostic accuracy for non-neoplastic specimens, US-guided CNB has been introduced as an alternative method.

Frozen Section of Parotid Gland Tumours: The Head and Neck Pathologist as a Key Member of the Surgical Team

Introduction: The aim of this study was to evaluate the impact of subspecialised head and neck versus general surgical pathologists on the reliability of the histopathologic evaluation during intraoperative consultation. Materials and Methods: The medical records of all patients who underwent a parotidectomy with frozen section between 2006 and 2021 were retrospectively evaluated. The frozen section was evaluated for sensitivity, specificity, accuracy, and predictive value. Assessment by two groups of pathologists (subspecialised head and neck versus general surgical pathologists) was compared, and the nature or types of misdiagnoses compared with final diagnoses on paraffin sections were analysed for the two groups. Results: Our study sample was made up of 669 cases. The mean age of patients was 57.7 years (range: 10−94 years). Of these, 490 patients had a benign lesion (73.2%), whereas 179 patients had a malignant lesion (26.8%). Frozen section had an overall accuracy of 97.6%, sensitivity for malignancy was 91.1%, specificity was 100%, PPV was 100%, and the NPV was 96.8%. The exact histologic subtype in the group of malignant tumours was correctly identified in FS in 89.4% of cases. A comparison of head and neck pathologists versus general surgical pathologists revealed a highly statistically significant difference concerning both overall detection of malignancy (p < 0.001) as well as correct identification of the histologic subtype (p < 0.001). Conclusion: Involvement of subspecialised head and neck pathologists in the intraoperative consultation for salivary gland tumours results in a gain of 19.8% more sensitivity, underlining the importance of specialisation in salivary gland pathology for the optimisation of frozen section quality.

Risk stratification of parotid neoplasms based on intraoperative frozen section and preoperative fine needle aspiration cytology

PURPOSE

This study aims to determine the relationship of frozen section (FS) to final histology and determine how incorporating FS may change preoperative malignancy risk estimates based on preoperative fine needle aspiration cytology (FNAC). The secondary aim is to determine if FS is useful in influencing intraoperative decision-making.

METHODS

Retrospective review of 426 intraoperative FS for parotidectomies performed for primary parotid lesions.

RESULTS

Risk of malignancy with a benign FS was 2.5%, with indeterminate 36.1%, and with malignant 100%. Incorporating FS to fine needle aspiration for cytology helped to stratify malignancy risk especially in the Milan categories of atypia of undetermined significance, neoplasm of uncertain malignant potential and non-diagnostic categories, where a malignant FS increased malignancy risk significantly. FS was only able to identify 11% of high-risk histological subtypes for which a neck dissection would be recommended.

CONCLUSIONS

FS may be used to stratify malignancy risk intraoperatively but has limited utility in clinical decision-making to perform a neck dissection and more extensive parotid resection in high-risk histological subtypes.

The role of frozen section biopsy for submandibular gland tumors

BACKGROUND

Although there have been several reports of the diagnostic accuracy of frozen section biopsy (FSB) for parotid gland tumors, few studies have focused on its diagnostic accuracy for submandibular gland tumors.

AIM/OBJECTIVES

This study aimed to investigate the necessity of FSB with regard to its diagnostic accuracy for submandibular gland tumors (SGTs).

MATERIALS AND METHODS

About 42 SGT patients underwent both fine-needle aspiration cytology (FNAC) and FSB between 2005 and 2020. The results of FNAC and FSB were analyzed and compared with the final histological diagnoses.

RESULTS

The respective sensitivity and specificity in detecting malignant tumors in 38 cases, excluding the four indeterminate FNAC cases, they were 0 and 97% for FNAC, and 100 and 97% for FSB. Considering the four indeterminate FNAC cases to be malignant, the respective sensitivity and specificity in detecting malignant tumors in the 42 cases were 50 and 92% for FNAC, and 100 and 95% for FSB.

CONCLUSIONS AND SIGNIFICANCE

FSB may be useful for malignancy detection as a final histological diagnosis in cases that are diagnosed as benign or indeterminate by FNAC in SGTs.

[Correlation between magnetic resonance imaging and extemporaneous and definitive histological examination of parotid gland tumors: a case series]

Parotid gland tumor is complex and poses diagnostic and therapeutic problems. The purpose of this study was to assess the role of extemporaneous examination in the management of patients with parotid gland tumors. We report a pro and retrospective analytical study of a series of cases of salivary gland tumors, whose data were collected in the ENT and in the department of cervical-facial Surgery at the University Hospital in Casablanca, between January 2012 and December 2015. Seventy two cases of parotid tumors were recorded. The sex-ratio (H/F) was 0.94, 0.76 for patients with benign tumors and 1.62 for patients with malignant tumors. The average age was 47 years (15- 75 years). The median of consultation time was 40 months. Clinical symptoms were dominated by parotid swelling (100%), pain in 25% of patients, facial palsy in 6%, and cervical adenopathies in 10%. Ultrasound was recommended in 80% of patients. MRI was performed in 26% of cases. All patients underwent surgery, 76% of patients underwent exofacial parotidectomies and 24% total conservative parotidectomies. This treatment was associated with ganglion resection in 24% of cases and radiotherapy in 24% of cases. Extemporaneous examination was performed in 71% of patients, its susceptibility was 89% and its specificity 88%. Definitive histological diagnosis was confirmed by anatomopathological examination in all cases. We confirmed benign and malignant tumors in 71% and 29% of cases respectively. Benign tumors were dominated by pleomorphic adenoma (59%), while malignant lesions were dominated by mucoepidermoid carcinoma (38%). The postoperative course was marked by: discrete haematoma in 4% of cases, transient facial palsy in 15%, superinfection of the wound in 3% and post-parotidectomy Frey´s syndrome in 3% of patients. One patient had labial recurrence of acinar cell carcinoma. No cases of death were noted. Parotid gland tumors are characterized by a great histological variability. Differentiation between malignant tumor and benign tumor is often difficult. Currently, MRI is the imaging test of choice. Extemporaneous examinationis is very useful intraoperatively when it is necessary to communicate with the pathologist. Multidisciplinary approach is adopted including ENT, oncological, radiotherapeutic, pathological and radiological approaches. Prognosis depends on the histological type, the stage of progression and treatment.

The role of frozen section biopsy for parotid gland tumour with benign fine-needle aspiration cytology

Objectives

This study focused on parotid gland tumours diagnosed as benign by fine-needle aspiration cytology and investigated the necessity of frozen section biopsy.

Methods

There were 104 cases of parotid gland tumour where fine-needle aspiration cytology was benign and frozen section biopsy was subsequently performed, between April 2006 and June 2016. In this retrospective study, the results of frozen section biopsy were analysed and compared with the final histological diagnosis.

Results

Among the 104 cases diagnosed as benign by fine-needle aspiration cytology, 102 cases and 2 cases were diagnosed as benign and malignant, respectively, by frozen section biopsy. The final histological diagnoses showed that 98 cases were benign and 6 cases were malignant. The sensitivity and specificity values of frozen section biopsy in detecting malignant tumours were 33 per cent and 100 per cent, respectively.

Conclusion

The necessity of frozen section biopsy in cases with benign fine-needle aspiration cytology may be low in parotid gland surgery.

Assessing the histological type and grade of primary parotid carcinoma by fine-needle aspiration and frozen section

OBJECTIVE

The aim of this study is to compare preoperative fine needle aspiration cytology (FNAC) and intraoperative frozen section (FS) for the correct identification of malignancy, histological grade, and histological type.

METHODS

FNAC was performed on all 105 patients and FS on 71 patients with parotid carcinoma.

RESULTS

The rate of correctly determining the histological grade by FNAC and FS was 32% and 73%, respectively. The correct diagnosis rate for both the histological type and grade by FNAC and FS was 20% and 48%, respectively.

CONCLUSIONS

The correct grading of both high and low/intermediate grade carcinoma is possible in 70-80% of patients by FS. If the histological grade is identified correctly, the extent of resection can usually be decided appropriately. Therefore, we should put emphasis on determining the histological grade.

[Intraoperative frozen section diagnosis of head and neck tumors: possibilities, limitations, pitfalls and tips for the daily practice]

Intraoperative consultation (synonym: frozen section diagnostics) has increasingly gained significance for the daily practice in head and neck surgery. The main aim of this investigation method which is usually associated with much stress and effort is to facilitate an optimal and timely oncological surgical treatment of neoplastic diseases with a minimum rate of postoperative functional disturbance. In order to achieve this purpose pathologists are expected to deliver as much correct information as possible to accurately influence intraoperative surgical decisions. At the same time this aim should be reached without significantly and unnecessarily increasing the workload for the pathology laboratory and without significantly inducing tissue artifacts. This would otherwise negatively influence the tissue quality for permanent section examination and consequently the overall quality of diagnosis and tumor staging. Thus, the quality and efficacy of frozen sections span a spectrum with the highest quality having the least possible false negative rate on the one hand and a false positive result of approximately zero on the other hand. Sticking to this approach would result in a high positive impact on the surgical treatment of a variety of neoplastic diseases and help to minimize or even eliminate the rate of medicolegal consequences.

Diagnostic value of ultrasound-guided core needle biopsy in patients with salivary gland masses

The salivary glands are unique in the diversity and complexity of their pathologies. Because fine needle aspiration cytology and frozen section are associated with major diagnostic difficulties, the authors analyzed the use of core needle biopsy (CNB) for the histologic assessment of salivary gland lesions. A systematic observational clinicopathologic quality assessment study was performed over 81 months including 161 CNB procedures in 76 patients with salivary gland pathologies. Adequate samples containing the target tissue were obtained in 73 patients. These samples revealed malignant disease in 45 (62%) patients, benign disease in 26 (36%) patients, and were inconclusive in 2 (3%) patients. Follow-up uncovered no false-positive or false-negative results. On the basis of secondary histologic and clinical follow-up, the statistical parameters were calculated as follows: sensitivity 94%; specificity 100%; accuracy 96%; positive predictive value 100%; negative predictive value 90%. The advantages and potential limitations of CNB in patients with salivary gland masses are discussed. CNB is a reliable biopsy technique for the assessment of salivary gland pathologies, although limitations remain for the subclassification of some neoplastic lesions. The authors recommend CNB as the biopsy technique of choice for a selection of indications.

A systematic review and meta-analysis of the diagnostic accuracy of frozen section for parotid gland lesions

We conducted a systematic literature review using MEDLINE and Embase to identify articles on diagnostic accuracy of frozen section (FS) for salivary gland lesions published between January 1, 1985, and December 31, 2010. We also reviewed the reference lists of all identified articles and conducted a forward search using Scopus to identify all articles citing the reference set. Meta-analysis was used to produce a summary receiver operating characteristic (SROC) curve from which summary estimates of sensitivity and specificity were obtained. Study quality was assessed using the Quality of Diagnostic Accuracy Study (QUADAS) survey. The accuracy of FS was compared with that of fine-needle aspiration cytology using results from an earlier review. A set of 13 studies (1,880 cases) with extractable data met our inclusion criteria. The summary estimates for the area under the SROC curve, FS sensitivity, and FS specificity are 0.99 (95% confidence interval [CI], 0.98-1.00), 0.90 (95% CI, 0.81-0.94), and 0.99 (95% CI, 0.98-1.00), respectively. FS has acceptable accuracy (90% sensitivity, 99% specificity) and is consistently accurate across study centers.

Usefulness of fine-needle aspiration in parotid diagnostics

PURPOSE

Fine needle aspiration (FNA) is a safe diagnostic technique that is widely employed for lesions of the head and neck. Among head and neck sites, the parotid gland is unique in the number, diversity, and peculiarity of its pathological processes. This complexity has prompted a great deal of discussion regarding the application of FNA to parotid masses, primarily focusing on the reliability of FNA as a diagnostic tool in guiding patient management.

METHODS

This review presents an analysis of the usefulness of FNA in differential diagnosis of parotid pathologies.

RESULTS

Recent studies have confirmed a wide range of accuracy rates for FNA evaluation of parotid masses, varying from 79% to 97%. These data cannot be uniformly anticipated across all diagnostic scenarios. FNA is notoriously unreliable in recognising the malignant nature of parotid carcinoma providing its precise classification and establishing its grade. A few malignant neoplasms are particularly prone to diagnostic error: acinic cell carcinoma is frequently interpreted as benign, and low-grade lymphomas are often discounted as inflammatory processes.

CONCLUSIONS

FNA cytology is useful in avoiding surgery (inflammatory lesions) or limiting surgical procedures (benign tumours). For planning the extent of surgery of malignant parotid tumours, the histological subtype and/or grade should be determined; therefore, a histological diagnosis by frozen section analysis is required. Moreover, reliance on FNA findings at the expense of clinical, radiographic, and intraoperative findings is unwarranted. Regardless of whether FNA is used routinely or selectively in patients with parotid masses, the findings should contribute to, and not replace, the overall diagnostic impression.

Parotid Tumors: Fine-Needle Aspiration and/or Frozen Section

Objective

The purpose of this study was to analyze and compare the value of fine-needle aspiration cytology (FNAC) and frozen section (FS) analysis in the assessment of parotid gland tumors.

Study Design

Chart review and cross-sectional analysis.

Subjects and Methods

FNAC and FS analysis of 110 parotid tumors, 68 malignancies and 42 benign tumors, were analyzed and compared with the final histopathologic diagnosis.

Results

The accuracy, sensitivity, and specificity of FNAC in detecting malignant tumors were 79 percent, 74 percent, and 88 percent, respectively. On FS analysis, the accuracy, sensitivity, and specificity in detecting malignant tumors were 94 percent, 93 percent, and 95 percent, respectively. The histologic tumor type was correctly diagnosed by FNAC and FS in 27 of 42 (64%) and 39 of 42 (93%) benign tumors, respectively, and in 24 of 68 (35%) and 49 of 68 (72%) malignant neoplasms, respectively.

Conclusion

The current analysis showed a superiority of FS compared with FNAC regarding the diagnosis of malignancy and tumor typing. FNAC alone is not prone to determine the surgical management of parotid malignancies.

Parotidectomy: ten-year review of 237 cases at a single institution

OBJECTIVE

To review a single surgeon's experience with parotidectomy with an emphasis on examining the appropriate use of partial superficial parotidectomy and the differences in early outcomes observed with the various types and extent of parotidectomy used.

STUDY DESIGN AND SETTING

A series of 237 patients who underwent parotidectomy over a 10-year period was reviewed.

RESULTS

Postoperative complications included facial nerve weakness (18%), sialocele (6.3%), wound infection (3.8%), hematoma (3.8%), and symptomatic Frey's syndrome (1.7%). More extensive surgical procedures, including complete superficial or total parotidectomy, were associated with a 2.7 times greater incidence of immediate postoperative facial nerve weakness compared with partial superficial parotidectomy.

CONCLUSION

Partial superficial parotidectomy is associated with a decreased incidence of transient postoperative facial nerve weakness compared with more extensive procedures such as complete superficial or total parotidectomy. Intraoperative frozen section was an accurate means of selecting patients for the partial superficial parotidectomy procedure.

SIGNIFICANCE

Partial superficial parotidectomy is an effective method for treating benign tumors confined to the superficial lobe.

FROZEN SECTION FOR PAROTID SURGERY: SHOULD IT BECOME ROUTINE?

BACKGROUND

The role of fine-needle aspiration (FNA) in salivary gland lesions as a preoperative diagnosis has always been under scrutiny. Several studies have shown that frozen section (FS) is accurate for pathological diagnosis and decision-making during the surgery. This study has been carried out to assess the accuracy of FNA and FS in parotid surgeries.

METHODS

All parotid lesions removed between July 1998 and June 2003 by the Department of Otolaryngology, Head and Neck unit at Monash Medical Centre were reviewed. FNA, FS and definitive pathology were collected and discrepancies were identified.

RESULTS

Eighty-five parotid tumours had been removed. Thirty-three were malignant in which squamous cell carcinoma was the most common. FS was able to differentiate benign tumours from malignant with 100% accuracy (30 cases). FS was able to alter the surgical decisions in six cases. FNA had been carried out in 62 cases, with sensitivity and specificity of 77.2 and 90%, respectively.

CONCLUSION

Frozen section in parotid surgery is accurate, inexpensive and may add important information that alters management and improves the outcome. The use of FS routinely in parotid surgery is recommended.

The role of fine needle aspiration in the evaluation of parotid masses

PURPOSE OF REVIEW

Fine needle aspiration is a safe diagnostic technique that is widely employed for lesions of the head and neck. Among head and neck sites, the parotid gland stands apart for the number, diversity and peculiarity of pathologic processes to target this structure. This matchless complexity has prompted a thoughtful discussion regarding the application of the fine needle aspiration to parotid masses--a discussion that has primarily focused on the reliability of the fine needle aspiration as a diagnostic tool, and on its utility in guiding patient management.

RECENT FINDINGS

Recent studies have confirmed a high overall accuracy rate for fine needle aspiration evaluation of parotid masses, ranging from 90 to 95%. At the same time, these soaring accuracy rates cannot be uniformly anticipated across all diagnostic scenarios. Fine needle aspiration is notoriously unreliable in recognizing the malignant nature of the parotid carcinoma, providing its precise classification, and establishing its grade. A few malignant neoplasms are particularly prone to diagnostic error. Acinic cell carcinoma is frequently interpreted as benign or even nonneoplastic; and low-grade lymphomas are often discounted as inflammatory processes.

SUMMARY

Parotid gland masses are not particularly conducive to diagnostic accuracy and precision by fine needle aspiration. Accordingly, indiscriminant reliance on the fine needle aspiration findings at the expense of the clinical, radiographic, and intraoperative findings is unwarranted. Whether one uses the fine needle aspiration routinely or selectively in patients with parotid masses, the fine needle aspiration findings should contribute to, not displace, the overall diagnostic impression.

Relative accuracy of fine-needle aspiration and frozen section in the diagnosis of lesions of the parotid gland

BACKGROUND

Both fine-needle aspiration (FNA) and frozen section (FS), although useful in preoperative and intraoperative management, have their advantages and pitfalls when used in the diagnosis of salivary gland lesions. The accuracy of each of these modalities has been assessed separately in many studies; a direct comparison of these techniques on a large cohort has not been well studied. Herein, we determine the relative accuracies of both FNA and FS in the diagnosis of salivary gland lesions.

METHODS

We reviewed a cohort of 220 cases of parotid gland FNA with histologic follow-up; FS was performed in 57 cases (26%). The sensitivity, specificity, and accuracy of FNA and FS were determined with respect to the final histologic diagnosis. For these calculations, benign diagnosis was considered negative, whereas a malignant diagnosis was considered positive. In addition, we re-reviewed the FNA and FS slides in cases that had conflicting FNA and FS results.

RESULTS

Of the 220 cases examined, the FNA diagnoses were as follows: benign (n = 142), malignant (n = 52), indeterminate (n = 14), and nondiagnostic (n = 12). Correlating these findings with the histologic findings, nine cases (4%) were false negative, whereas 12 (5%) were false positive. The sensitivity, specificity, and accuracy for FNA when diagnostic were 86%, 92%, and 90%, respectively. In 57 cases with FS, seven (12%) were false negative, whereas none were false positive. The FS was able to change to benign four diagnoses that were malignant by FNA and provide a diagnosis for five nondiagnostic FNAs. The sensitivity, specificity, and accuracy for FS were 77%, 100%, and 88%, respectively. The sensitivity, specificity, and accuracy for FNA and FS combined were 90%, 100%, and 95%, respectively.

CONCLUSIONS

Both FNA and FS provide a similar accuracy. FS may be useful if FNA is nondiagnostic and may also be useful in confirming or refuting malignancy in some cases. Hence, both techniques are complementary to each other in the diagnosis of salivary gland lesions.

Diagnostic accuracy of fine-needle aspiration cytology and frozen section in primary parotid carcinoma

BACKGROUND

The low incidence and histologic heterogeneity of primary parotid carcinomas makes it difficult to evaluate the value of preoperative fine-needle aspiration cytology (FNAC) and intraoperative frozen section (FS) analysis. In the current study, the authors reviewed a single institution's experience regarding the preoperative and intraoperative diagnostic value of FNAC and FS in primary salivary gland carcinomas.

METHODS

Between January 1990 and December 2002, 108 primary parotid carcinomas were resected at the Department of Otorhinolaryngology, Head and Neck Surgery at the University of Berne, Inselspital (Berne, Switzerland). Included in the study were a total of 101 carcinomas with preoperative FNAC results in 88 tumors and/or intraoperative FS results in 45 tumors. In a retrospective study, the results of FNAC and FS were analyzed and compared with the corresponding histopathologic diagnoses.

RESULTS

The cytologic findings were true-positive for malignancy in 63 tumors (72%), false-negative in 22 tumors (25%), and nondiagnostic in 3 tumors (3%). The tumor grading was correct in 29 of 63 tumors (46%), and the exact tumor typing was correct in 27 of 63 (43%) true-positive tumors. The FS findings were true-positive for malignancy in 43 of 45 tumors (96%), the tumor grading was correct in 35 of 45 tumors (78%), and the tumor typing was correct in 32 of 45 tumors (71%). Overall, at the time of surgery, of the 101 parotid carcinomas, the tumor was known to be malignant in 83 tumors (82%), and the correct grade and the exact tumor type were known in 55 tumors (54%) and 48 tumors (48%), respectively.

CONCLUSIONS

FNAC recognized malignancy in 72% of tumors, but it could not be relied upon to provide an accurate tumor grading or typing. Therefore, FNAC alone is not prone to determine the surgical management of primary parotid carcinomas. The current analysis showed the statistically significant superiority of FS compared with FNAC regarding the diagnosis of malignancy, tumor grading, and tumor typing in primary parotid carcinomas.