Frozen section accurately allows pathological characterization of endometrial cancer in patients with a preoperative ambiguous or inconclusive diagnoses: our experience

Hysterectomy with sentinel lymph node dissection in the setting of preoperative endometrial intraepithelial neoplasia and an endometrial stripe ≥20 mm: a cost-effectiveness analysis

OBJECTIVES

Routine lymph node assessment in patients with endometrial intraepithelial neoplasia is institution and surgeon-dependent without clear guidelines. We sought to determine if routine sentinel lymph node (SLN) dissection at the time of laparoscopic hysterectomy for patients with a preoperative diagnosis of endometrial intraepithelial neoplasia and a preoperative ultrasound with endometrial stripe ≥20 mm is cost-effective.

METHODS

A decision model was created to perform two cost-effectiveness analyses: (1) hysterectomy with frozen section versus hysterectomy with SLN dissection in patients with a preoperative diagnosis of endometrial intraepithelial neoplasia and an endometrial stripe of 20 mm or greater, and (2) the same options in all patients with a preoperative diagnosis of endometrial intraepithelial neoplasia. Costs obtained from Centers for Medicare and Medicaid Services and event probabilities and quality of life utility values were obtained through literature review.

RESULTS

In the case of preoperative endometrial stripe ≥20 mm, hysterectomy with SLN dissection cost $2469 more than hysterectomy with frozen section and gained 0.010 quality adjusted life years, or $44,997/quality-adjusted life years gained. In one-way sensitivity analyses, SLN dissection remained the favored strategy at a willingness to pay threshold of $100,000/quality-adjusted life years unless chronic lower extremity lymphedema after full lymphadenectomy had a likelihood <13.1% (base case value 18.1%); otherwise, SLN dissection was favored with individual variation of all other parameters over plausible ranges. When considering all patients with endometrial intraepithelial neoplasia, hysterectomy with frozen section was favored, with results most sensitive to variation of lymphedema risk after full lymphadenectomy.

CONCLUSION

Hysterectomy with SLN dissection in patients with a preoperative endometrial stripe ≥20mm on ultrasound is cost-effective when compared with hysterectomy with frozen section.

Confounders of intraoperative frozen section pathology during glioma surgery

Although frozen section pathology (FSP) is commonly performed during surgery for glioma-suspicious lesions, confounders of accuracy are largely unknown. FSP and final diagnosis were compared in 398 surgeries for glioma-suspicious lesions. Diagnostic accuracy, risk factors for diagnostic shift from neoplastic to non-neoplastic tissue and vice versa according to the final diagnosis, and the impact on intraoperative and postoperative decision-making were analyzed. Diagnostic shift occurred in 70 cases (18%), and sensitivity, specificity, and the positive (PPV) and negative (NPV) predictive value of FSP were 82.5%, 77.8%, 99.4%, and 9.3%, respectively. No correlations between shift and patients' age and sex, sample fluorescence or volume, tumor location, correct information on the pathology form, final high- or low-grade histology, or molecular alterations were found (p > .05, each). Shift was more common after irradiation (25% vs 15%; p = .025) or chemotherapy (26% vs 15%; p = .022) than in treatment naïve cases and correlated with the type of surgery (p = .002). FSP altered intraoperative decision-making in 25 cases (6%). Postoperative shift led to repeated surgery in 12 patients (3%). In 45 cases, in which FSP and final diagnosis based on the same tissue, shift occurred in only 5 patients (11%), and sensitivity, specificity, PPV, and NPV for FSP were 77.4%, 78.6%, 88.9%, and 61.1%, respectively. No correlations between diagnostic shift and any of the analyzed variables were found (p > .05, each). Although accuracy of FSP during glioma surgery is sufficient, moderate NPV should be considered during intraoperative decision-making. While confounders are sparse, accuracy might be increased by repeated sampling. Diagnostic shift rarely alters postoperative treatment strategy.

Intraoperative frozen section in gynaecology cancers with special reference to ovarian tumours: time to "unfreeze" the pitfalls in the path of the Derby horse of Oncology

PURPOSE

In an oncological set up the role of frozen section biopsy is undeniable. They serve as an important tool for surgeon's intraoperative decision making but the diagnostic reliability of intraoperative frozen section may vary from institute to institute. The surgeon should be well aware of the accuracy of the frozen section reports in their setup to enable them to take decisions based on the report. This is why we had conducted a retrospective study at Dr B. Borooah Cancer Institute, Guwahati, Assam, India to find out our institutional frozen section accuracy.

METHODS

The study was conducted from 1st January 2017 to 31st December 2022 (5 years). All gynaecology oncology patients who were operated on during the study period and had an intraoperative frozen section done were included in the study. Patients who had incomplete final histopathological report (HPR) or no final HPR were excluded from the study. Frozen section and final histopathology report were compared and analysed and discordant cases were analysed based on the degree of discordancy.

RESULTS

For benign ovarian disease, the IFS accuracy, sensitivity and specificity are 96.7%, 100% and 93%, respectively. For borderline ovarian disease the IFS accuracy, sensitivity and specificity are 96.7%, 80% and 97.6%, respectively. For malignant ovarian disease the IFS accuracy, sensitivity and specificity are 95.4%, 89.1% and 100%, respectively. Sampling error was the most common cause of discordancy.

CONCLUSION

Intraoperative frozen section may not have 100% diagnostic accuracy but still it is the running horse of our oncological institute.

It is not the time to abandon intraoperative frozen section in endometrioid adenocarcinoma: A large-scale, multi-center, and retrospective study

INTRODUCTION

Stage IB (deep myometrial invasion) high-grade endometrioid adenocarcinoma (EA), regardless of LVSI status, is classified into high-intermediate risk groups, requiring surgical lymph node staging. Intraoperative frozen section (IFS) is commonly used, but its adequacy and reliability vary between reports. Hence, we determined the utility of IFS in identification of high-risk factors, including deep myometrial invasion and high-grade.

METHOD

We retrospectively analyzed 9,985 cases operated with hysterectomy and diagnosed with FIGO stage I/II EA in postoperative paraffin section (PS) results at 30 Chinese hospitals from 2000 to 2019. We determined diagnostic performance of IFS and investigated whether the addition of IFS to preoperative biopsy and imaging could improve identification of high-risk factors.

RESULTS

IFS and postoperative PS presented the highest concordance in assessing deep myometrial invasion (Kappa: 0.834), followed by intraoperative gross examination (IGE Kappa: 0.643), MRI (Kappa: 0.395), and CT (Kappa: 0.207). IFS and postoperative PS presented the highest concordance for high-grade EA (Kappa: 0.585) compared to diagnostic curettage (D&C 0.226) and hysteroscope (Hys 0.180). Sensitivity and specificity for detecting deep myometrial invasion were 86.21 and 97.20% for IFS versus 51.72 and 88.81% for MRI, 68.97 and 94.41% for IGE. These figures for detecting high-grade EA were 58.21 and 96.50% for IFS versus 16.42 and 98.83% for D&C, 13.43 and 98.64% for Hys. Parallel strategies, including MRI-IFS (Kappa: 0.626), D&C-IFS (Kappa: 0.595), and Hys-IFS (Kappa: 0.578) improved the diagnostic efficiencies of individual preoperative examinations. Based on the high sensitivity of IFS, parallel strategies improved the sensitivities of preoperative examinations to 89.66% (MRI), 64.18% (D&C), 62.69% (Hys), respectively, and these differences were statistically significant (p = 0.000).

CONCLUSION

IFS presented reasonable agreement rates predicting postoperative PS results, including deep myometrial invasion and high-grade. IFS helps identify high-intermediate risk patients in preoperative biopsy and MRI and guides intraoperative lymphadenectomy decisions in EA.

Evaluation of the role of intraoperative frozen section and magnetic resonance imaging in endometrial cancer

OBJECTIVE

To evaluate the accuracy of preoperative endometrial biopsy and magnetic resonance imaging (MRI) of endometrial cancer compared with that of intraoperative frozen section.

METHODS

This retrospective study included 264 patients who underwent surgery with intraoperative frozen section for endometrial cancer at our institution between 2014 and 2018. Diagnosis was determined by histologic type, grade, and myometrial invasion. Concordance rate, sensitivity, and specificity of preoperative diagnosis and intraoperative frozen diagnosis were calculated, in comparison to the final pathologic diagnosis.

RESULTS

Preoperative and intraoperative diagnoses showed no statistically significant difference in determining histologic type and grade (P = 0.152). Intraoperative diagnosis showed higher sensitivity for endometrioid carcinoma grade 3 and other types, and higher specificity for grade 1. For myometrial invasion, intraoperative diagnosis showed significantly higher concordance rate than preoperative MRI findings (P < 0.01). Intraoperative diagnosis showed higher sensitivity and specificity in patients with and without myometrial invasion, respectively.

CONCLUSION

Higher agreement between intraoperative and final diagnoses, especially in myometrial invasion, suggests that intraoperative frozen section is a good indicator for appropriate surgical procedure decision making.

Preoperative and intraoperative assessment of myometrial invasion in patients with FIGO stage I non-endometrioid endometrial carcinoma-a large-scale, multi-center, and retrospective study

INTRODUCTION

Myometrial invasion is a prognostic factor for lymph node metastases and decreased survival in non-endometrioid endometrial carcinoma patients. Herein, we explored the mode of myometrial invasion diagnosis in FIGO stage I non-endometrioid carcinoma and evaluated the differences in diagnostic efficiency among intraoperative frozen section (IFS), intraoperative gross examination (IGE), magnetic resonance imaging (MRI), and computed tomography (CT) in clinical practice. Finally, we suggested which test should be routinely performed.

METHOD

This was a historical cohort study nationwide with 30 centers in China between January 2000 and December 2019. Clinical data, including age, histology, method of myometrial invasion evaluation (MRI, CT, IGE, and IFS), and final diagnosis of postoperative paraffin sections, were collected from 490 non-endometrioid endometrial carcinoma (serous, clear cell, undifferentiated, mixed carcinoma, and carcinosarcoma) women in FIGO stage I.

RESULTS

Among the 490 patients, 89.59% presented myometrial invasion. The methods reported for myometrial invasion assessment were IFS in 23.47%, IGE in 69.59%, MRI in 37.96%, and CT in 10.20% of cases. The highest concordance was detected between IFS and postoperative paraffin sections (Kappa = 0.631, accuracy = 93.04%), followed by IGE (Kappa = 0.303, accuracy = 82.40%), MRI (Kappa = 0.131, accuracy = 69.35%), and CT (Kappa = 0.118, accuracy = 50.00%). A stable diagnostic agreement between IFS and the final results was also found through the years (2000-2012: Kappa = 0.776; 2013-2014: Kappa = 0.625; 2015-2016: Kappa = 0.545; 2017-2019: Kappa = 0.652).

CONCLUSION

In China, the assessment of myometrial invasion in non-endometrioid endometrial carcinoma is often performed via IGE, but the reliability is relatively low in contrast to IFS. In clinical practice, IFS is a reliable method that can help accurately assess myometrial invasion and intraoperative decision-making (lymph node dissection or not). Hence, it should be routinely performed in non-endometrioid endometrial carcinoma patients.

Are blood parameters assessed before taking frozen sections useful in gynecological oncology?

Background/Aim: Inflammatory processes are often implicated in oncology, and inflammatory markers and indices have been much studied in this context. In gynecological surgery, frozen sections have proven valuable in decision-making. Here we aim to identify laboratory parameters that correlate with frozen section results and thus develop new indices in neoplastic decision-making. Methods: In this retrospective cross-sectional study at Bursa Yüksek İhtisas Training and Research Hospital, we evaluated 139 patients diagnosed with adnexal mass and endometrial intraepithelial neoplasia. We divided the patients whose frozen sections were reported as malignant, borderline, or benign into three groups and compared the pre-operative complete blood parameters. Results: The mean age of our patients was 57.3 (11.5) years, and frozen section reports were benign in 33 (23.7%), borderline in 43 (30.9%), and malignant in 63 (45.3%) patients. The mean corpuscular volume and mean platelet volume values ​​were different, and this difference was significant between borderline and malignant groups in post-hoc analyses (P = 0.04 and P = 0.03, respectively). While the percentage of lymphocytes was lower in malignant groups, the percentage of neutrophils was higher (P = 0.01 and P = 0.03, respectively). According to post-hoc analysis, the percentage of neutrophils differs between benign and malignant groups (P = 0.05). The difference in lymphocyte percentage was significant between benign-borderline and benign-malignant groups (P = 0.02, P = 0.05; respectively). The blood neutrophil/lymphocyte ratio was higher in the malignant groups compared to the other two groups (P = 0.02). We used the Multi Linear Regression Analysis method to analyze the factors that play a role in predicting the frozen outcome as malignant. Accordingly, the model with the best performance used lymphocyte percentage, neutrophil/lymphocyte ratio, and Ca-125 parameters (P = 0.03). Conclusion: This study indicates that inflammatory markers may give a clue about the character of the neoplastic mass before oncology surgery. Thus, we can make new contributions to the surgical and clinical approach in the literature by developing new malignancy indices.

Clear cell endometrial carcinoma precursors: presentation of two cases and diagnostic issues

BACKGROUND

The precursors of clear cell endometrial carcinoma (CC-EC) are still undefined. Here, we deal with the diagnostic issues related to CC-EC precursors by presenting a morphological, immunophenotypical and molecular study of two representative cases and discussing the relevant literature.

CASE PRESENTATION

Our and previous cases suggest that clear cell endometrial intraepithelial carcinoma (CC-EIC) is a real entity, which may be distinguished from metaplastic/reactive changes and from its serous counterpart. CC-EIC appears associated with atrophic polyps and may be diagnosed based on morphological and immunophenotypical features of CC-EC in the absence of invasive disease. We described a p53-mutant putative precursor characterized by high-grade nuclei in the absence of other distinctive features. Two putative low-grade precursors resembled atypical tubal metaplasia and endometrial intraepithelial neoplasia, although immunohistochemistry could not support their relationship with CC-EC.

CONCLUSIONS

In conclusion, pathologists should be aware of the existence of CC-EIC, since its correct diagnosis may be crucial for a correct patient management. Although several putative earlier precursors have been described, they does not show univocal features that allow their recognition in the common practice. Further studies are necessary in this field.

New Pathological and Clinical Insights in Endometrial Cancer in View of the Updated ESGO/ESTRO/ESP Guidelines

Endometrial carcinoma represents the most common gynecological cancer in Europe and the USA. Histopathological classification based on tumor morphology and tumor grade has played a crucial role in the management of endometrial carcinoma, allowing a prognostic stratification into distinct risk categories, and guiding surgical and adjuvant therapy. In 2013, The Cancer Genome Atlas (TCGA) Research Network reported a large scale molecular analysis of 373 endometrial carcinomas which demonstrated four categories with distinct clinical, pathologic, and molecular features: POLE/ultramutated (7% of cases) microsatellite instability (MSI)/hypermutated (28%), copy-number low/endometrioid (39%), and copy-number high/serous-like (26%). In the present article, we report a detailed histological and molecular review of all endometrial carcinoma histotypes in light of the current ESGO/ESTRO/ESP guidelines. In particular, we focus on the distribution and prognostic value of the TCGA groups in each histotype.

Could a 2D/3D US based model be helpful in the assessment of myometrial invasion at time of intraoperative frozen section? A pilot study

BACKGROUND

The assessment of myometrial invasion is a pivotal step in the preoperative staging of endometrial cancer. Intraoperative frozen section (FS) represents a reliable tool in directing surgeon's choices. Preoperative transvaginal ultrasound (US) showed high accuracy in evaluating myometrial invasion. This study aimed to understand if the application of a standardized ultrasonographic protocol for the pre-operative evaluation of myometrial invasion can help pathologists in improving the accuracy of FS. Furthermore, the agreement between US and FS in the assessment of myometrial invasion was assessed.

METHODS

Sixty-six patients who underwent surgery for endometrial cancer were analyzed. Preoperative 2D/3D ultrasound was performed in all the patients. Myometrial invasion was estimated by subjective assessment and objective measurement techniques. Data from US were reported to pathologists through a prefilled form with depth and site of the maximum myometrial invasion. Diagnostic performance of US and FS were compared having the definitive histological examination as the gold standard.

RESULTS

Influenced by the information given by our 3D US-model, FS showed a 90% sensitivity and a 93% specificity, with a 93% PPV and an 89% NPV. The agreement with histology was strong (K=0.824). Myometrial invasion was missed at the level of the isthmus by FS just in one case. Subjective assessment was confirmed as the most reliable ultrasonographic technique in assessing myometrial invasion, with 90% sensitivity, 78% specificity, 80% PPV and 89% NPV. The agreement with histology was substantial (K=0.68).

CONCLUSIONS

The application of a preoperative 2D/3D US assessment would seem to help pathologists in detecting myometrial invasion in difficult areas of the uterus such as the isthmus, reducing downstaging and overtreatment.

Diagnostic Pitfalls Related to Morular Metaplasia in Endometrioid Carcinoma: An Underestimated Issue

Here, we present a case that highlights the crucial pitfalls related to the presence of morular metaplasia (MM) in endometrioid carcinoma, which are insufficiently recognized in the routine pathology practice. A 45-year-old woman underwent hysterectomy with rectosigmoidectomy due to a 11-cm mass involving uterus, right ovary, and rectosigmoid colon. Histologically, the lesion appeared as a predominantly solid carcinoma with a minor glandular component. Results of the first immunohistochemical analysis suggested a colorectal origin (PAX8-, CK7-, WT1-, hormone receptors-, and CDX2+ in the absence of mucinous features). Subsequent immunohistochemistry (nuclear β-catenin+, CD10+, and low ki67 in the solid areas) supported a diagnosis of endometrioid carcinoma with diffuse MM. This case remarks that morphological and immunohistochemical features of MM may conceal the glandular architecture and the typical immunophenotype of endometrioid carcinomas. Acknowledging the diagnostic issues related to MM appears crucial to avoid misdiagnosis and inappropriate patient management.

Accuracy of intra-operative frozen section in guiding surgical staging of endometrial cancer

PURPOSE

Surgery consists the main treatment of endometrial cancer; however, decision of lypmhadenectomy is controversial. Intra-operative frozen section (FS) is commonly used in guiding surgical staging; nevertheless, there are different reports regarding its adequacy and reliability. Aim of this study is to assess accuracy of FS in predicting paraffin section (PS) results in patients with endometrium cancer.

METHODS

Data of 223 cases, who were operated for endometrial cancer at a tertiary hospital in 2012-2019, were analyzed retrospectively. Histological type, grade, tumor diameter, depth of myometrial invasion, and cervical and adnexal involvement in frozen and paraffin section were evaluated. Positive and negative predictive values and accuracy of frozen results in predicting paraffin results for each parameter was assessed. Statistical significance was taken as 0.05 in all tests.

RESULTS

Accuracy of FS in predicting PS results were 76.23% for histology, 75.45% for grade, 85.31% for depth of myometrial invasion, and 95.45% for tumor diameter. Surgery, based on FS results, caused undertreatment in 4 patients, while metastatic lymph node ratios were found in only 35.3-50.0% of cases who had high risk parameters at FS.

CONCLUSION

Our FS results have reasonable accuracy rates in predicting PS results, in comparison with the previous literature. However, even if the high risk parameters detected in FS predict PS accurately, absence of lymph node involvement in all cases with high risk parameters indicates that FS-based triage cannot prevent unnecessary lymphadenectomies.

Diagnostic performance of intraoperative assessment in grade 2 endometrioid endometrial carcinoma

Abstract

Background

Endometrial carcinoma is the most common gynecologic malignancy in developed countries. Grade 2 carcinoma is associated with pelvic lymph-node metastasis, depending on selected risk factors. Intraoperative assessment (IOA) can identify patients at risk for lymph node metastasis who should undergo staging surgery. Our objective was to establish the diagnostic precision of IOA in determining the need for surgical staging in grade 2 endometrioid endometrial carcinoma.

Methods

Two hundred twenty-two patients underwent IOA. Results were compared to the final pathology report. The accuracy of the IOA parameters was calculated. Variables were evaluated in patients with positive versus negative IOA. Overall and disease-free survivals were calculated according to IOA, lymphadenectomy, and nodal metastasis.

Results

IOA was positive in 80 patients. It showed an accuracy of 76.13% when compared with the postoperative assessment. The best individual parameter was myometrial invasion. Nodal metastasis was observed in 16 patients in the positive IOA group and 7 patients in the negative group. Patients with lymph node metastasis had a 5-year overall survival rate of 80.9%, whereas patients without metastasis had a 5-year overall survival rate of 97.9%.

Conclusions

IOA is an adequate tool to identify high-risk patients in grade 2 endometrial carcinoma. Myometrial invasion is the individual parameter that yields the highest diagnostic precision.

An Analysis of Clinical, Surgical, Pathological and Molecular Characteristics of Endometrial Cancer According to Mismatch Repair Status. A Multidisciplinary Approach

Since 2016, our hospital has applied tumor testing with immunohistochemistry (IHC) in endometrial cancer in order to detect mutations of mismatch repair genes (MMR). All cases with MMR deficiency proteins expression are sent for genetic testing, except those with MLH1 protein deficiency, in which case genetic testing is performed if negative for promoter hypermethylation. The primary aim of this study was to investigate the ability of our algorithm to identify Lynch syndrome (LS). The Secondary aims were to investigate the relationship between MMR status and clinicopathological features and prognosis of primary endometrial cancer (EC). From January 2016 to December 2018, 239 patients with EC were retrospectively analyzed and subdivided according to MMR status. Patients were divided in three groups: MMR proficient, LS and Lynch-like cancer (LLC). LS was characterized by a lower age and BMI, more use of contraceptive and less use of hormonal replacement therapy, nulliparity and a trend versus a better prognosis. LLC appeared more related to MMR proficient than LS and exhibited a more aggressive behavior. Our multidisciplinary approach permitted a correct diagnosis of germline mutation in patients with newly diagnosis EC and it confirmed clinicopathologic and prognostic characteristics of LS.

Accuracy of preoperative endometrial biopsy and intraoperative frozen section in predicting the final pathological diagnosis of endometrial cancer

BACKGROUND

Histotype and grade of endometrial cancer (EC) are prognostic factors of nodal involvement and thus of survival. Preoperative biopsy (PB) and intraoperative frozen section (FS) are usually used to guide surgical staging on which the choice of adjuvant therapy will be based successively.

OBJECTIVE

The aim of this study was to assess the agreement rate between PB and FS with final diagnosis (FD) in a series of surgically resected EC.

MATERIALS

All patients submitted to hysterectomy for EC or atypical endometrial hyperplasia in the Reggio Emilia Province hospitals from 2007 to 2018 were included. Concordance rate differences in histotype, grading, myoinvasion, risk of recurrence between PB, FS and FD were assessed with Fisher's exact test and Mc Nemar contingency test.

RESULTS

A total of 352 patients were identified. For 345 patients it was possible to compare PB and FD results. FS examination was performed in 201/352 (57%) cases, while for 21/352 (6%) patients only an intraoperative macroscopic evaluation was done; in the remaining women, FS-exam was omitted. In 14/201 (7%) cases the tumor wasn't grossly identifiable and the random FS-sampling wasn't able to find the tumor site. High diagnostic concordance of tumor type between PB and FD was observed: no significant differences were registered in type 1 and type 2-endometrial cancer identification (83%, 73%, p = 0.121). Significant differences (p = 0.005) were observed comparing FS and FD results: 95% of type 1-ECs were correctly diagnosed by FS, while only 76% of type 2-ECs received a correct diagnosis on FS. PB showed a concordance with FD among tumor grading close to 55% whilst concordance achieved 71% grouping low grade (G1-G2) EC. No significant differences in FS and FD concordance rate were observed between tumor grades. Concordance for low grade was significantly higher than for high grade ECs (89% vs 50%, respectively, p value = 0.014). The concordance rate in evaluating the myoinvasion status between FS and FD was 80% (n: 199 patients), reaching 99% after combining the first 2 groups (0-49% vs ≥ 50%). Twenty-two cases underwent only intraoperative macroscopic evaluation of the myoinvasion, with an accuracy of 91%: only in 1 case the invasion of the cervical stroma was not detected (Stage II), and 1 case the patient was overstaged as Ib. Discrepancies were observed in FS capacity to correctly predict the final ESMO risk group in stage I patients: FS resulted particularly reliable in predicting a low-risk (concordance with FD: 91%) while the accuracy sharply decreased for intermediate- and high-risk patients (62% and 40%, respectively). To investigate the usefulness of FS in EC management, we compared patients who underwent FS (FS-group) or not (no-FS-group). Especially for low risk patients, the FS significantly increased the adequacy of surgical treatment from 53% (no-FS-group) to 72% (FS-group) (p = 0.016).

CONCLUSIONS

FS remains a useful tool to tailor surgery in EC-patients, avoiding secondary surgery to complete staging particularly in patients with AH + AHBA, low and intermediate risk ECs that could benefit from adjuvant therapy.