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Objective: To assess the influence of geographies and race on the survival outcomes in patients diagnosed with cervical squamous cell carcinoma (CSCC) across three continents., Methods: This multicontinental retrospective study was conducted in 8 hospitals across Asia, Europe, and North America (NA). Clinicopathologic data of 595 patients with presumed early stages of CSCC, treated surgically, with curative intent was collected. Descriptive analysis and Cox regression models were produced., Results: A total of 595 patients, consisting of 445 (74.8 %) white, 75 (12.6 %) Blacks, and 75 (12.6 %) Asian patients were included. Geographical distribution comprised 69 % of patients from NA, 22 % from Europe, and 9 % from Asia. The median age at diagnosis was 46 years. The median overall survival (OS) and relapse-free survival (RFS) were 22.09 years and 21.19 years, respectively. Patient characteristics varied significantly across geographical regions, except for consensus tumor grade. Patients in Europe from middle-income countries with limited CC screening had a substantially higher risk of death than those in NA (HR, 1.79; 95 % CI, 1.13 to 2.79; p = 0.015). Patients from single center in Japan had higher risk of relapse than those from the four heterogeneous NA centers (sub-distribution hazard ratio, 2.19; 95 % CI, 1.22 to 3.95; p = 0.009), although OS did not differ significantly. Race remained statistically insignificant for survival outcomes across the three continents but seemed to influence survival outcomes in NA centers., Conclusion: Our study highlights impact of geographies and races on CSCC survival outcomes, emphasizing the need of considering these factors when developing targeted interventions against CSCC., Competing Interests: Declaration of competing interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (Copyright © 2024. Published by Elsevier Inc.)

Context.—: Endocervical adenocarcinoma is divided into human papillomavirus (HPV)-associated (HPVA) and HPV-independent (HPVI) in the 5th edition of the World Health Organization (WHO) tumor classification launched in 2020. However, the validity of the morphologic criteria used for biopsy specimens in real-world practice remains undetermined., Objective.—: To validate the utility of the 5th edition of the WHO classification for biopsy samples, focusing on its diagnostic criteria with the aid of ancillary studies., Design.—: We retrieved 217 cases of endocervical adenocarcinoma from 6 institutions, in which glass slides of both biopsy and resection specimens were available for review. Concordance between the biopsy and resection specimen diagnoses was evaluated. For discordant diagnoses, an algorithmic approach with ancillary studies proposed by the international group was applied to confirm their utility to improve the accuracy of biopsy diagnosis., Results.—: The biopsy diagnosis matched the resection specimen diagnosis in 197 cases (concordance rate, 91%; κ = 0.75). The concordance rate was significantly higher for HPVA than HPVI (95% versus 81%, P = .001). There were no significant differences in the proportions of HPVA and HPVI or the accuracy of biopsy diagnosis between the participating institutions. All 19 discordant cases with unstained glass slides available were accurately recategorized as HPVA or HPVI using HPV in situ hybridization; p16 immunohistochemistry was positive in 3 of 9 cases of gastric-type HPVI that were negative by in situ hybridization., Conclusions.—: The 5th edition of the WHO criteria for biopsy diagnosis of endocervical adenocarcinoma distinguishes HPVA from HPVI well when ancillary studies are adequately applied., Competing Interests: The authors have no relevant financial interest in the products or companies described in this article., (© 2024 College of American Pathologists.)

We compared grading systems and examined associations with tumor stroma and survival in patients with cervical squamous cell carcinoma. Available tumor slides were collected from 10 international institutions. Broders tumor grade, Jesinghaus grade (informed by the pattern of tumor invasion), Silva pattern, and tumor stroma were retrospectively analyzed; associations with overall survival (OS), progression-free survival (PFS), and presence of lymph node metastases were examined. Binary grading systems incorporating tumor stromal changes into Broders and Jesinghaus grading systems were developed. Of 670 cases, 586 were reviewed for original Broders tumor grade, 587 for consensus Broders grade, 587 for Jesinghaus grade, 584 for Silva pattern, and 556 for tumor stroma. Reproducibility among grading systems was poor (κ = 0.365, original Broders/consensus Broders; κ = 0.215, consensus Broders/Jesinghaus). Median follow-up was 5.7 years (range, 0-27.8). PFS rates were 93%, 79%, and 71%, and OS rates were 98%, 86%, and 79% at 1, 5, and 10 years, respectively. On univariable analysis, original Broders ( P < 0.001), consensus Broders ( P < 0.034), and Jesinghaus ( P < 0.013) grades were significant for OS; original Broders grade was significant for PFS ( P = 0.038). Predictive accuracy for OS and PFS were 0.559 and 0.542 (original Broders), 0.542 and 0.525 (consensus Broders), 0.554 and 0.541 (Jesinghaus grade), and 0.512 and 0.515 (Silva pattern), respectively. Broders and Jesinghaus binary tumor grades were significant on univariable analysis for OS and PFS, and predictive value was improved. Jesinghaus tumor grade ( P < 0.001) and both binary systems (Broders, P = 0.007; Jesinghaus, P < 0.001) were associated with the presence of lymph node metastases. Histologic grade has poor reproducibility and limited predictive accuracy for squamous cell carcinoma. The proposed binary grading system offers improved predictive accuracy for survival and the presence of lymph none metastases., Competing Interests: N.A.R. reports research funding paid to the institution from GRAIL. A.I. reports consulting fees from Mylan. The remaining authors declare no conflict of interest., (Copyright © 2023 by the International Society of Gynecological Pathologists.)

We aimed to determine the frequency of human papillomavirus-independent (HPVI) cervical squamous cell carcinoma (SCC) and to describe clinicopathologic characteristics. Among 670 patients with surgically treated SCCs in an established multi-institutional cohort, 447 had available tissue. Tissue microarrays were constructed and studied by in situ hybridization (ISH) for high-risk and low-risk human papillomavirus (HPV) mRNA and immunohistochemistry for p16 and p53. Tumors were HPVI if negative by HPV ISH and they failed to show diffuse p16 positivity by immunohistochemistry, and human papillomavirus-associated (HPVA) if positive by HPV ISH. Ten HPVI SCCs and 435 HPVA SCCs were identified; 2 cases were equivocal and excluded from analysis. The overall rate of HPVI SCC was low (2%) but was higher among older patients (7% in patients above 60 y of age and 17% in patients above 70 y of age). Compared with HPVA, patients with HPVI SCC were significantly older (median age, 72 vs. 49, P <0.001) and diagnosed at a higher stage (40% vs. 18% with stage III/IV disease, P =0.055). p53 expression was varied; 2 cases (20%) had null expression and 8 (80%) had wild-type expression. HPVI SCCs were heterogenous, with keratinizing, nonkeratinizing, and warty morphologies observed. Several cases had a precursor lesion reminiscent of differentiated vulvar intraepithelial neoplasia, with prominent basal atypia and hypereosinophilia or a basaloid-like morphology. Two patients (20%) had distant recurrences within 12 months, and 3 (30%) died of disease during follow-up. HPVI SCCs are rare tumors that are more common among older patients with higher stage disease and have important clinical and histologic differences from HPVA SCCs., Competing Interests: Conflicts of Interest and Source of Funding: Funded in part by the National Institutes of Health (NIH)/National Cancer Institute (NCI) Cancer Center Support Grant P30 CA008748. Outside the submitted work, N.R.A.-R. reports research funding paid to the institution from GRAIL. A.I. reports consulting fees from Mylan. For the remaining authors none were declared., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Objective: We evaluated clinicopathologic parameters of patients with cervical squamous cell carcinoma (SCC) who were treated with initial surgical management and assessed their relation to survival outcomes. Specifically, we evaluated the relation between extent of lymphovascular invasion (LVI) and survival outcomes., Methods: All available tumor slides from patients with initially surgically treated cervical SCC were collected from 10 institutions and retrospectively analyzed. Standard clinicopathological parameters, tumor stroma, and extent of LVI were assessed (focal: <5 spaces, extensive: ≥5 spaces). PFS and OS were evaluated using Kaplan-Meier methodology. Univariable and multivariable Cox proportional hazards models were created to determine prognostic survival-related risk factors., Results: A total of 670 tumor samples were included in the analysis. Median age at diagnosis was 47 years (IQR: 38-60), 457 patients (72%) had a 2018 International Federation of Gynecology and Obstetrics (FIGO) stage I tumor, and 155 tumors (28%) were flat and/or ulcerated. There were 303 nonkeratinizing tumors (51%), 237 keratinizing tumors (40%), and 356 histologic grade 2 tumors (61%). Quantifiable LVI was present in 321 cases (51%; 23% focal and 33% extensive). On multivariable analysis for PFS, extensive and focal LVI had worse outcomes compared to negative LVI (HR: 2.38 [95% CI: 1.26-4.47] and HR: 1.54 [95% CI: 0.76-3.11], respectively; P = 0.02). The difference did not reach statistical significance for OS., Conclusion: Presence of LVI is a prognostic marker for patients with cervical SCC. Quantification (extensive vs. focal vs. negative) of LVI may be an important biomarker for oncologic outcome., Competing Interests: Declaration of Competing Interest Outside the submitted work, N.R. Abu-Rustum reports research funding paid to the institution from GRAIL. A. Iasonos reports consulting fees from Mylan. All other authors have no potential conflicts of interest to disclose., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Although both the 2014 and 2020 World Health Organization (WHO) criteria require unequivocal glandular and squamous differentiation for a diagnosis of cervical adenosquamous carcinoma (ASC), in practice, ASC diagnoses are often made in tumors that lack unequivocal squamous and/or glandular differentiation. Considering the ambiguous etiologic, morphologic, and clinical features and outcomes associated with ASCs, we sought to redefine these tumors. We reviewed slides from 59 initially diagnosed ASCs (including glassy cell carcinoma and related lesions) to confirm an ASC diagnosis only in the presence of unequivocal malignant glandular and squamous differentiation. Select cases underwent immunohistochemical profiling as well as human papillomavirus (HPV) testing by in situ hybridization. Of the 59 cases originally classified as ASCs, 34 retained their ASC diagnosis, 9 were reclassified as pure invasive stratified mucin-producing carcinomas, 10 as invasive stratified mucin-producing carcinomas with other components (such as HPV-associated mucinous, usual-type, or ASCs), and 4 as HPV-associated usual or mucinous adenocarcinomas with benign-appearing squamous metaplasia. Two glassy adenocarcinomas were reclassified as poorly differentiated HPV-associated carcinomas based on morphology and immunophenotype. There were no significant immunophenotypic differences between ASCs and pure invasive stratified mucin-producing carcinomas with regard to HPV and other markers including p16 expression. Although limited by a small sample size, survival outcomes seemed to be similar between all groups. ASCs should be diagnosed only in the presence of unequivocal malignant glandular and squamous differentiation. The 2 putative glassy cell carcinomas studied did not meet our criteria for ASC and categorizing them as such should be reconsidered., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 by the International Society of Gynecological Pathologists.)

Cervical carcinoma remains one of the most common cancers affecting women worldwide, despite effective screening programs being implemented in many countries for several decades. The International Collaboration on Cancer Reporting (ICCR) dataset for cervical carcinoma was first developed in 2017 with the aim of developing evidence-based standardized, consistent and comprehensive surgical pathology reports for resection specimens. This 4th edition update to the ICCR dataset on cervical cancer was undertaken to incorporate major changes based upon the updated International Federation of Obstetricians and Gynecologists (FIGO) staging for carcinoma of the cervix published in 2018 and the 5th Edition World Health Organization (WHO) Classification of Female Genital Tumors published in 2020 and other significant developments in pathologic aspects of cervical cancer. This updated dataset was developed by a panel of expert gynecological pathologists and an expert gynecological oncologist, with a period of open consultation. The revised dataset includes "core" and "noncore" elements to be reported; these are accompanied by detailed explanatory notes and references providing the rationale for the updates. Standardized reporting using datasets such as this helps facilitate consistency and accuracy, data collection across different sites and comparison of epidemiological and pathologic parameters for quality and research purposes., Competing Interests: The authors declare no conflict of interest., (Copyright © 2022 by the International Society of Gynecological Pathologists.)

Silva invasion pattern can help predict lymph node metastasis risk in endocervical adenocarcinoma. We analysed Silva pattern of invasion and lymphovascular invasion to determine associations with clinical outcomes in stage IA and IB1 endocervical adenocarcinomas. International Federation of Gynecology and Obstetrics (FIGO; 2019 classification) stage IA-IB1 endocervical adenocarcinomas from 15 international institutions were examined for Silva pattern, presence of lymphovascular invasion, and other prognostic parameters. Lymph node metastasis status, local/distant recurrences, and survival data were compared using appropriate statistical tests. Of 399 tumours, 152 (38.1%) were stage IA [IA1, 77 (19.3%); IA2, 75 (18.8%)] and 247 (61.9%) were stage IB1. On multivariate analysis, lymphovascular invasion (p=0.008) and Silva pattern (p<0.001) were significant factors when comparing stage IA versus IB1 endocervical adenocarcinomas. Overall survival was significantly associated with lymph node metastasis (p=0.028); recurrence-free survival was significantly associated with lymphovascular invasion (p=0.002) and stage (1B1 versus 1A) (p=0.002). Five and 10 year overall survival and recurrence-free survival rates were similar among Silva pattern A cases and Silva pattern B cases without lymphovascular invasion (p=0.165 and p=0.171, respectively). Silva pattern and lymphovascular invasion are important prognostic factors in stage IA1-IB1 endocervical adenocarcinomas and can supplement 2019 International Federation of Gynecology and Obstetrics staging. Our binary Silva classification system groups patients into low risk (patterns A and B without lymphovascular invasion) and high risk (pattern B with lymphovascular invasion and pattern C) categories., (Copyright © 2022 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.)

HIK1083 and trefoil factor 2 (TFF2) are known to be expressed in gastric-type carcinoma (GAS), but they do not reliably mark all GASs, and focal expression can be missed in biopsy specimens. We aimed to investigate whether claudin-18 and alpha-methylacyl-CoA racemase (AMACR) could be surrogate markers to separate GAS from other types of endocervical adenocarcinoma (ECA) and to compare their usefulness with that of HIK1083 and TFF2. Claudin-18 and AMACR immunohistochemistry was performed, and the results were compared with that of TFF2 and HIK1083, using whole sections of 75 ECAs (22 GASs and 53 non-GASs) and 179 ECAs with tissue microarrays (TMAs). TMAs were built to simulate the assessment of immunohistochemical stains in small biopsies. Any membranous (claudin-18) or cytoplasmic/membranous (AMACR, TFF2, HIK1083) staining of >5% of tumor cells was considered positive. Of 75 ECAs with whole sections, claudin-18 was significantly more frequently expressed in GASs (21/22) compared with non-GASs (8/53) (P<0.01). In ECAs with TMAs, claudin-18 expression was significantly frequent in GASs (15/23, 65.2%) than in non-GASs (3/152, 2.0%; all usual-type) (P<0.01). All claudin-18-positive GASs showed intense staining except 1 case. Claudin-18 shared the same degree of sensitivity and specificity with HIK1083 and TFF2. Three clear cell carcinomas were positive for claudin-18, but none showed intense staining. AMACR was expressed in a subset of ECAs and showed no impact in distinguishing between GAS and other ECAs. Our results suggest that claudin-18 is a promising surrogate marker to separate GAS from other types of ECA, including clear cell carcinoma., Competing Interests: Conflicts of Interest and Source of Funding: Supported in part through the NIH/NCI Cancer Center Support Grant P30 CA008748 (R.A.S., K.J.P.). The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Gastric-type cervical adenocarcinoma (GCA) is an aggressive type of endocervical adenocarcinoma characterized by mucinous morphology, gastric-type mucin, lack of association with human papillomavirus (HPV) and resistance to chemo/radiotherapy. We characterized the landscape of genetic alterations in a large cohort of GCAs, and compared it with that of usual-type HPV-associated endocervical adenocarcinomas (UEAs), pancreatic adenocarcinomas (PAs) and intestinal-type gastric adenocarcinomas (IGAs). GCAs (n = 68) were subjected to massively parallel sequencing targeting 410-468 cancer-related genes. Somatic mutations and copy number alterations (CNAs) were determined using validated bioinformatics methods. Mutational data for UEAs (n = 21), PAs (n = 178), and IGAs (n = 148) from The Cancer Genome Atlas (TCGA) were obtained from cBioPortal. GCAs most frequently harbored somatic mutations in TP53 (41%), CDKN2A (18%), KRAS (18%), and STK11 (10%). Potentially targetable mutations were identified in ERBB3 (10%), ERBB2 (8%), and BRAF (4%). GCAs displayed low levels of CNAs with no recurrent amplifications or homozygous deletions. In contrast to UEAs, GCAs harbored more frequent mutations affecting cell cycle-related genes including TP53 (41% vs 5%, p < 0.01) and CDKN2A (18% vs 0%, p = 0.01), and fewer PIK3CA mutations (7% vs 33%, p = 0.01). TP53 mutations were less prevalent in GCAs compared to PAs (41% vs 56%, p < 0.05) and IGAs (41% vs 57%, p < 0.05). GCAs showed a higher frequency of STK11 mutations than PAs (10% vs 2%, p < 0.05) and IGAs (10% vs 1%, p < 0.05). GCAs harbored more frequent mutations in ERBB2 and ERBB3 (9% vs 1%, and 10% vs 0.5%, both p < 0.01) compared to PAs, and in CDKN2A (18% vs 1%, p < 0.05) and KRAS (18% vs 6%, p < 0.05) compared to IGAs. GCAs harbor recurrent somatic mutations in cell cycle-related genes and in potentially targetable genes, including ERBB2/3. Mutations in genes such as STK11 may be used as supportive evidence to help distinguish GCAs from other adenocarcinomas with similar morphology in metastatic sites.

The incidence of endocervical adenocarcinoma, the second most common cervical cancer in the world, has been on the rise. While most cervical cancers are squamous cell carcinomas and associated with high-risk oncogenic human papillomavirus (HPV), approximately 15% of endocervical adenocarcinomas, which now represent about one quarter of all cervical cancers, are HPV-independent. In this review, we will focus on the shortcomings of historical histologic classification systems of female genital tract tumors as they pertain to endocervical adenocarcinomas, and we will highlight the advantages of the new International Endocervical Adenocarcinoma Criteria and Classification system, which forms the basis for the WHO 2020 classification. We will cover the various histologic types, subtypes, and variants of endocervical adenocarcinoma with regard to morphology, immunophenotype, molecular genetics, HPV status and differential diagnosis, and we will provide International Society of Gynecological Pathologists recommendations for diagnosing these tumors., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 International Society of Gynecological Pathologists. Published by Wolters Kluwer Health, Inc. on behalf of the International Society of Gynecological Pathologists.)

Histopathologic classification of endocervical adenocarcinomas (EAC) has recently changed, with the new system based on human papillomavirus (HPV)-related morphologic features being incorporated into the 5th edition of the WHO Blue Book (Classification of Tumours of the Female Genital Tract). There has also been the introduction of a pattern-based classification system to assess invasion in HPV-associated (HPVA) endocervical adenocarcinomas that stratifies tumors into 3 groups with different prognoses. To facilitate the introduction of these changes into routine clinical practice, websites with training sets and test sets of scanned whole slide images were designed to improve diagnostic performance in histotype classification of endocervical adenocarcinoma based on the International Endocervical Adenocarcinoma Criteria and Classification (IECC) and assessment of Silva pattern of invasion in HPVA endocervical adenocarcinomas. We report on the diagnostic results of those who have participated thus far in these educational websites. Our goal was to identify areas where diagnostic performance was suboptimal and future educational efforts could be directed. There was very good ability to distinguish HPVA from HPV-independent adenocarcinomas within the WHO/IECC classification, with some challenges in the diagnosis of HPV-independent subtypes, especially mesonephric carcinoma. Diagnosis of HPVA subtypes was not consistent. For the Silva classification, the main challenge was related to distinction between pattern A and pattern B, with a tendency for participants to overdiagnose pattern B invasion. These observations can serve as the basis for more targeted efforts to improve diagnostic performance., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 International Society of Gynecological Pathologists. Published by Wolters Kluwer Health, Inc. on behalf of the International Society of Gynecological Pathologists.)

Two cases of pediatric lung cancer (in 23-month-old and 6-year-old boys) resulting from mother-to-infant transmission of uterine cervical tumors were incidentally detected during routine next-generation sequencing of paired samples of tumor and normal tissue. Spontaneous regression of some lesions in the first child and slow growth of the tumor mass in the second child suggested the existence of alloimmune responses against the transmitted tumors. Immune checkpoint inhibitor therapy with nivolumab led to a strong regression of all remaining tumors in the first child. (Funded by the Japan Agency for Medical Research and Development and others; TOP-GEAR UMIN Clinical Trials Registry number, UMIN000011141.)., (Copyright © 2021 Massachusetts Medical Society.)

Microcystic, elongated, and fragmented (MELF) pattern of myometrial invasion is correlated with lymphovascular invasion (LVI) and lymph node metastases in uterine endometrioid carcinoma but has not been described in endocervical adenocarcinoma (ECA). A total of 457 ECAs were collected, and clinical/morphologic parameters correlated with follow-up data. Potential associations between MELF pattern and age, human papillomavirus status, tumor size/grade, LVI, lymph node metastases, Silva pattern were analyzed. Statistical analyses of overall survival (OS), disease-free survival, progression-free survival (PFS) were conducted using Kaplan-Meier analysis, and compared using the Log-rank test. Of 292 ECAs analyzed, 94 (32.19%) showed MELF invasion pattern (MELF-positive). Significant statistical correlation was found between MELF-positive and tumor size (P=0.0017), LVI (P=0.007), Silva pattern (P=0.0005); age, human papillomavirus status, tumor grade, lymph node metastases did not correlate. Fifty-five of 292 patients recurred (18.83%): 18/94 (19.14%) MELF-positive, 37/198 (18.68%) MELF-negative. PFS in MELF-positive: 77.2% and 64.5% at 5 and 10 yr, respectively; PFS in MELF-negative: 82% and 68.5% at 5 and 10 yr, respectively. On multivariate analysis for PFS and other prognostic parameters, only LVI was statistically significant (P=0.001). OS in MELF-positive was 86% and 74.1% at 5 and 10 yr, respectively; OS in MELF-negative, was 89.7% and 86% at 5 and 10 yr, respectively. Median survival was worse in MELF-positive (199.8 mo) versus MELF-negative (226.1 mo); this was not statistically significant. On multivariate analysis for OS and other prognostic parameters, only tumor stage was statistically significant (P=0.002). In ECAs, MELF is not independently associated with survival. Pathologic characteristics of MELF-positive (size, LVI, Silva pattern) versus MELF-negative tumors differ significantly.

The International Endocervical Adenocarcinoma Criteria and Classification (IECC) categorizes endocervical adenocarcinomas (ECAs) on the basis of morphologic features linked to etiology (ie, human papilloma virus [HPV] infection), resulting in separation of ECAs into HPV-associated (HPVA) and unassociated or non-HPVA (NHPVA) types. NHPVAs are reported to be large and present at high stage in older individuals. Our aim was to examine the clinical outcomes in these tumor types. Full slide sets of 205 ECAs were collected from 7 institutions worldwide and classified on the basis of IECC criteria and the presence or absence of HPV. Clinical and morphologic parameters were correlated with follow-up data. Statistical analysis of overall survival (OS), disease-free survival (DFS), and progression-free survival (PFS) were conducted using the Kaplan-Meier survival analysis and compared using the log-rank test for univariate analysis. Multivariate survival analysis was conducted, and the survival endpoints considered were OS, DFS, and PFS. Statistically significant survival differences (OS, DFS, and PFS) were found when comparing the following categories: HPVA>NHPVA (ie, survival was superior in the setting of HPVAs), including patients treated with surgery followed by adjuvant therapy; usual-type HPVA>mucinous HPVA; FIGO grade 3 HPVA>NHPVA; HPVA>NHPVA, both with lymphovascular invasion; and HPVA>NHPVA in patients with pelvic recurrences. Although there were trends favoring HPVA outcomes over those of NHPVA, these differences were not statistically significant in the following categories: mucinous HPVA versus NHPVA; HPVA versus NHPVA, both with lymph node metastases at presentation; and HPVA versus NHPVA in patients with distant metastasis. Survival for both HPVA and NHPVA was similar when surgery without adjuvant therapy was used. FIGO grading did not have prognostic significance in HPVAs. Multivariable analysis of HPVAs indicated nearly significant statistical associations between stage and both OS and DFS (P=0.07 and 0.06, respectively), and between Silva invasion pattern and OS (P=0.09). Multivariate analysis of NHPVAs indicated a statistically significant association between OS and age (P=0.03), stage (P=0.02) and tumor size (P=0.002), and between DFS and stage (P=0.004) and tumor size (P=0.004). Multivariate analysis of HPVAs and NHPVAs together revealed nearly significant associations between OS and HPV status and stage (both [P=0.06]). For DFS, stage was a significant variable (P=0.04), whereas HPV status and tumor size were nearly significant (P=0.06 and 0.07, respectively). Clinical outcome studies support the idea that the IECC classification not only separates ECAs on the basis of HPV status (usually assessed on H&E slides), but also has important clinical relevance.

Although 2014 World Health Organization criteria require unequivocal glandular and squamous differentiation for a diagnosis of cervical adenosquamous carcinoma, in practice, adenosquamous carcinoma diagnoses are often made in tumors that lack unequivocal squamous and/or glandular differentiation. Considering the ambiguous etiologic, morphological, and clinical features and outcomes associated with adenosquamous carcinomas, we sought to redefine these tumors. We reviewed slides from 59 initially diagnosed adenosquamous carcinomas (including glassy cell carcinoma and related lesions) to confirm an adenosquamous carcinoma diagnosis only in the presence of unequivocal malignant glandular and squamous differentiation. Select cases underwent immunohistochemical profiling as well as human papillomavirus (HPV) testing by in situ hybridization. Of the 59 cases originally classified as adenosquamous carcinomas, 34 retained their adenosquamous carcinoma diagnosis, 9 were reclassified as pure invasive stratified mucin-producing carcinomas, 10 as invasive stratified mucin-producing carcinomas with other components (such as HPV-associated mucinous, usual-type, or adenosquamous carcinomas), and 4 as HPV-associated usual or mucinous adenocarcinomas with benign-appearing squamous metaplasia. Two glassy cell carcinomas were reclassified as poorly differentiated usual-type carcinomas based on morphology and immunophenotype. There were significant immunophenotypic differences between adenosquamous carcinomas and pure invasive stratified mucin-producing carcinomas with regard to HPV (p < 0.0001), PAX8 (p = 0.038; more in adenosquamous carcinoma), p40 (p < 0.0001; more in adenosquamous carcinoma), p63 (p = 0.0018; more in adenosquamous carcinoma) and MUC6 (p  < 0.0001; less in adenosquamous carcinoma), HNF-1beta (p = 0.0023), vimentin (p = 0.0003), p53 (p = 0.0004), and CK7 (p = 0.0002) expression. Survival outcomes were similar between all groups. Adenosquamous carcinomas should be diagnosed only in the presence of unequivocal malignant glandular and squamous differentiation. The two putative glassy cell carcinomas studied did not meet our criteria for adenosquamous carcinoma, and categorizing them as such should be reconsidered.

Gastric-type endocervical adenocarcinoma (GAS) is a recently described diagnostic entity originally characterized as a tumor with (1) voluminous cytoplasm that is (2) clear or pale eosinophilic, and (3) cells showing distinct cell borders. Since the initial tumor description there has been accumulating experience that the neoplasm, in addition to classic features, may show a wide spectrum of morphologic appearances. This paper describes and illustrates cases of GAS with focal or diffuse findings that include: densely eosinophilic cytoplasm, foamy cytoplasm, goblet cells, glands with elongated, stratified nuclei, glands with small cuboidal cells, glands with flattened cells, papillary growth, single cell infiltration and infiltration with microcystic elongated and fragmented pattern. All these patterns may bring up a differential diagnosis with other cervical malignancies such as usual, intestinal, endometrioid, clear cell, serous, and mesonephric adenocarcinoma. The paper describes the patterns of immunostaining of respective lesions that may aid in the diagnostic process and summarizes the main points of the differential diagnosis. GAS is associated with somatic and germline STK11 mutations and TP53 mutations but is invariably negative for human papilloma virus when tumor only is tested. It shows variation in incidence between countries. Awareness of the spectrum of morphologic appearances in GAS is important for accurate and confident diagnosis. Correct identification of GAS is important due to its propensity for ovarian and other distant metastases, markedly worse prognosis as compared with usual endocervical adenocarcinoma, and its relative resistance to chemotherapy.

The International Endocervical Adenocarcinoma Criteria and Classification was developed to separate endocervical adenocarcinomas (ECAs) into 2 main categories on the basis of morphology such as human papilloma virus-associated (HPVA) and non-human papilloma virus-associated adenocarcinomas. We aimed to improve the diagnostic accuracy of International Endocervical Adenocarcinoma Criteria and Classification by performing a comprehensive immunohistochemical evaluation and constructing objective immunohistochemical-based algorithms for the classification of these tumors. Tissue microarrays were constructed from 297 of 409 cases used to develop the original classification. Immunostains included p16, p53, estrogen receptor (ER), progesterone receptor, androgen receptor, Vimentin, CK7, CK20, HER2, HIK1083, MUC6, CA-IX, SATB2, HNF-1beta, napsin A, PAX8, CDX2, GATA3, p63, p40, and TTF-1. High-risk human papilloma virus (HR-HPV) was detected by in situ hybridization (ISH) using probes against E6 and E7 mRNA expressed in 18 different virus types. Vimentin, ER, and progesterone receptor were expressed in a significant minority of ECAs, mostly HPVAs, limiting their use in differential diagnosis of endometrioid carcinoma when unaccompanied by HPV-ISH or p16. HR-HPV ISH had superior sensitivity, specificity, and negative and positive predictive values compared with p16, as published previously. HNF-1beta did not have the anticipated discriminatory power for clear cell carcinoma, nor did MUC6 or CA-IX for gastric-type carcinoma. HNF-1beta and napsin A were variably expressed in clear cell carcinoma, with HNF-1beta demonstrating less specificity, as it was ubiquitously expressed in gastric-type carcinoma and in the majority of HPV-associated mucinous (predominantly intestinal-type and invasive ECA resembling stratified mucin-producing intraepithelial lesion [iSMILE]) and usual-type carcinomas. HIK1083 was expressed in nearly half of gastric-type carcinomas, but not in the vast majority of other subtypes. GATA3 was positive in 10% of usual-type adenocarcinomas and in single examples of other subtypes. Rare gastric-type and HPVA mucinous carcinomas displayed HER2 overexpression. Androgen receptor was positive in 6% of usual-type adenocarcinomas. Aberrant p53 expression was found in only 3.6% of usual-type HPVA carcinomas, but it was more prevalent in mucinous (intestinal type and iSMILE) HPVAs and non-human papilloma virus-associates (particularly in gastric-type carcinoma, >50% of cases). The following diagnostic classification algorithms were developed with the above data. Carcinomas without overt cytoplasmic mucin (endometrioid, usual-type endocervical, clear cell, and mesonephric carcinomas) can be subclassified using HR-HPV ISH, ER, and GATA3, whereas carcinomas with easily appreciated cytoplasmic mucin (endometrioid carcinoma with mucinous features, HPVA mucinous, and gastric-type carcinomas) can be subclassified with HR-HPV ISH and ER.

We sought to classify endocervical adenocarcinomas (ECAs) based on morphologic features linked to etiology (ie, human papillomavirus [HPV] infection), unlike the World Health Organization 2014 classification. The International Endocervical Adenocarcinoma Criteria and Classification (IECC criteria), described herein, distinguishes between human papillomavirus-associated adenocarcinoma (HPVA), recognized by the presence of luminal mitoses and apoptosis seen at scanning magnification, and no or limited HPVA features (nonhuman papillomavirus-associated adenocarcinoma [NHPVA]). HPVAs were then subcategorized based on cytoplasmic features (mostly to provide continuity with preexisting classification schemes), whereas NHPVAs were subclassified based on established criteria (ie, gastric-type, clear cell, etc.). Complete slide sets from 409 cases were collected from 7 institutions worldwide. Tissue microarrays representing 297 cases were constructed; immunohistochemistry (p16, p53, vimentin, progesterone receptor) and chromogenic in situ hybridization using an RNA-based probe set that recognizes 18 varieties of high-risk HPV were performed to validate IECC diagnoses. The 5 most common IECC diagnoses were usual-type (HPVA) (73% of cohort), gastric-type (NHPVA) (10%), mucinous adenocarcinoma of HPVA type, including intestinal, mucinous not otherwise specified, signet-ring, and invasive stratified mucin-producing carcinoma categories (9%), clear cell carcinoma (NHPVA) (3%) and adenocarcinoma, not otherwise specified (2%). Only 3 endometrioid carcinomas were recognized and all were NHPVA. When excluding cases thought to have suboptimal tissue processing, 90% and 95% of usual-type IECC cases overexpressed p16 and were HPV, whereas 37% and 3% of NHPVAs were p16 and HPV, respectively. The 1 HPV gastric-type carcinoma was found to have hybrid HPVA/NHPVA features on secondary review. NHPVA tumors were larger and occurred in significantly older patients, compared with HPVA tumors (P<0.001). The high-risk HPV chromogenic in situ hybridization probe set had superior sensitivity, specificity, and positive and negative predictive values (0.955, 0.968, 0.992, 0.833, respectively) compared with p16 immunohistochemistry (0.872, 0.632, 0.907, 0.545, respectively) to identify HPV-related usual carcinoma and mucinous carcinoma. IECC reliably segregates ECAs into HPVA and NHPVA types using morphology alone. This study confirms that usual-type ECAs are the most common type worldwide and that mucinous carcinomas comprise a mixture of HPVA and NHPVA, with gastric-type carcinoma being the major NHPVA type. Endometrioid and serous carcinomas of the endocervix are extraordinarily rare. Should clinical outcomes and genomic studies continue to support these findings, we recommend replacement of the World Health Organization 2014 criteria with the IECC 2017.

Objective: Gastric-type mucinous carcinoma (GAS) is a novel variant of mucinous carcinoma of the uterine cervix, characterized by aggressive clinical behavior and absence of high-risk human papillomavirus. We conducted this study to evaluate the chemosensitivity of GAS compared with that of usual-type endocervical adenocarcinoma (UEA) in patients who had been enrolled in our previous study., Methods: Of 52 patients from our previous phase 2 study (SGSG005) of neoadjuvant chemotherapy with docetaxel and carboplatin for stage IB2 to IIB nonsquamous cervical cancer, 47 (stage IB2, 12; stage IIA2, 7; stage IIB, 28) were enrolled in this study with written informed consent. The biopsy specimens before neoadjuvant chemotherapy and surgical specimens after chemotherapy were centrally reviewed based on the updated World Health Organization classification (2014)., Results: Of 47 patients with nonsquamous cell carcinoma, 20 (42.6%) were diagnosed with UEA, 13 (27.7%) with GAS, 12 (25.5%) with adenosquamous carcinoma, and 1 patient each (2%) with small cell carcinoma and serous carcinoma. Consequently, 33 patients, consisting of 20 patients with UEA and 13 patients with GAS, were eligible for the current study. The response rate of GAS was significantly lower than that of UEA (46.2% vs 85.0%, P = 0.048). Of 16 cases of stage II UEA, 11 (68.8%) were downstaged on microscopic examination of postsurgical specimens, but none of the 8 patients with stage II GAS showed any response (P < 0.01). Two inoperative tumors were GAS. With a median follow-up duration of 56 months, the 5-year progression-free and overall survival rates of GAS were significantly worse than those of UEA (38.5% vs 75.0% [P = 0.011] and 36.9% vs 90.0% [P < 0.001], respectively)., Conclusions: These findings suggest that GAS should be distinguished from UEA by its chemoresistance, necessitating an alternative treatment strategy established for this distinct subtype of endocervical adenocarcinoma.

Adenocarcinomas exhibiting gastric differentiation represent a recently described and uncommon subtype of non-human papillomavirus (HPV)-related cervical adenocarcinoma. They comprise a spectrum from a well-differentiated variant (adenoma malignum/mucinous variant of minimal deviation adenocarcinoma) to a more poorly differentiated overtly malignant form, generally referred to as gastric-type adenocarcinoma. Rarely, such tumors have also been described as primary vaginal neoplasms. Gastric-type adenocarcinomas exhibit considerable morphologic overlap with adenocarcinomas originating outside the female genital tract, especially mucinous adenocarcinomas arising in the pancreas and biliary tract. Moreover, they often metastasize to unusual sites, such as the ovary and peritoneum/omentum, where they can be mistaken for metastatic adenocarcinomas from other, nongynecologic sites. There is little information regarding the immunophenotype of gastric-type adenocarcinomas, and knowledge of this is important to aid in the distinction from other adenocarcinomas. In this study, we undertook a detailed immunohistochemical analysis of a large series of cervical (n=45) and vaginal (n=2) gastric-type adenocarcinomas. Markers included were cytokeratin (CK)7, CK20, CDX2, carcinoembryonic antigen, CA125, CA19.9, p16, estrogen receptor, progesterone receptor, MUC6, PAX8, PAX2, p53, hepatocyte nuclear factor 1 beta, carbonic anhydrase IX, human epidermal receptor 2 (HER2), and mismatch repair (MMR) proteins. All markers were classified as negative, focal (<50% of tumor cells positive), or diffuse (≥50% tumor cells positive) except for p53 (classified as "wild-type" or "mutation-type"), HER2 (scored using the College of American Pathologists guidelines for gastric carcinomas), and MMR proteins (categorized as retained or lost). There was positive staining with CK7 (47/47-45 diffuse, 2 focal), MUC6 (17/21-6 diffuse, 11 focal), carcinoembryonic antigen (25/31-12 diffuse, 13 focal), carbonic anhydrase IX (20/24-8 diffuse, 12 focal), PAX8 (32/47-20 diffuse, 12 focal), CA125 (36/45-5 diffuse, 31 focal), CA19.9 (11/11-8 diffuse, 3 focal), hepatocyte nuclear factor 1 beta (13/14-12 diffuse, 1 focal), CDX2 (24/47-4 diffuse, 20 focal), CK20 (23/47-6 diffuse, 17 focal), and p16 (18/47-4 diffuse, 14 focal). Most cases were negative with estrogen receptor (29/31), progesterone receptor (10/11), PAX2 (18/19), and HER2 (25/26). p53 showed "wild-type" and "mutation-type" staining in 27 of 46 and 19 of 46 cases, respectively. MMR protein expression was retained in 19 of 20 cases with loss of MSH6 staining in 1 patient with Lynch syndrome. Molecular studies for HPV were undertaken in 2 tumors, which exhibited diffuse "block-type" immunoreactivity with p16, and both were negative. This is the first detailed immunohistochemical study of a large series of gastric-type adenocarcinomas of the lower female genital tract. Our results indicate immunophenotypic overlap with pancreaticobiliary adenocarcinomas but suggest that PAX8 immunoreactivity may be especially useful in distinguishing gastric-type adenocarcinomas from pancreaticobiliary and other nongynecologic adenocarcinomas, which are usually negative. Diffuse "block-type" p16 immunoreactivity in a cervical adenocarcinoma is not necessarily indicative of a high-risk HPV-associated tumor.

Gastric-type adenocarcinoma of the uterine cervix (GAS) is a rare variant of mucinous endocervical adenocarcinoma not etiologically associated with human papillomavirus (HPV) infection, with minimal deviation adenocarcinoma (MDA) at the well-differentiated end of the morphologic spectrum. These tumors are reported to have worse prognosis than usual HPV associated endocervical adenocarcinoma (UEA). A retrospective review of GAS was performed from the pathology databases of 3 institutions spanning 20 years. Stage, metastatic patterns, and overall survival were documented. Forty GAS cases were identified, with clinical follow-up data available for 38. The tumors were subclassified as MDA (n=13) and non-MDA GAS (n=27). Two patients were syndromic (1 Li-Fraumeni, 1 Peutz-Jeghers). At presentation, 59% were advanced stage (FIGO II to IV), 50% had lymph node metastases, 35% had ovarian involvement, 20% had abdominal disease, 39% had at least 1 site of metastasis at the time of initial surgery, and 12% of patients experienced distant recurrence. The metastatic sites included lymph nodes, adnexa, omentum, bowel, peritoneum, diaphragm, abdominal wall, bladder, vagina, appendix, and brain. Follow-up ranged from 1.4 to 136.0 months (mean, 33.9 mo); 20/38 (52.6%) had no evidence of disease, 3/38 (7.9%) were alive with disease, and 15/38 (39.5%) died of disease. Disease-specific survival at 5 years was 42% for GAS versus 91% for UEA. There were no survival differences between MDA and non-MDA GAS. GAS represents a distinct, biologically aggressive type of endocervical adenocarcinoma. The majority of patients present at advanced stage and pelvic, abdominal, and distant metastases are not uncommon.

Objective: To clarify the preoperative differential diagnosis and management of minimal deviation adenocarcinoma (MDA) and lobular endocervical glandular hyperplasia (LEGH), a multicenter study was performed., Methods: A total of 112 patients who underwent conization or a hysterectomy for suspected MDA were collected from 24 hospitals. The pathological diagnosis in each case was determined by a central pathological review board. The diagnostic significance of clinicopathologic findings including results of magnetic resonance imaging (MRI), Papanicolaou (Pap) smears, and testing for gastric mucin was analyzed., Results: The central pathological review identified 37 cases of Nabothian cyst or tunnel cluster, 54 cases of LEGH, 6 cases of MDA, 11 cases of adenocarcinoma, and 4 cases of benign disease. Lobular endocervical glandular hyperplasia was often associated with adenocarcinoma in situ, MDA, and mucinous adenocarcinoma. Three MDA patients had a recurrence, whereas none of LEGH patients had a recurrence irrespective of the type of surgery. On MRI, LEGH appeared as a characteristic multicystic lesion with an inner solid component, whereas MDA showed a predominantly solid pattern. A Pap smear or gastric mucin alone had limited diagnostic power. However, a combination of these findings is useful; that is, a cystic structure with inner solid components on MRI associated with mild glandular atypia and gastric mucin strongly suggested LEGH (24/26, 92%). A solid structure with atypical glandular cells was indicative of MDA or adenocarcinoma (5/5, 100%)., Conclusions: The combination of MRI, Pap smears, and gastric mucin will improve the accuracy of the preoperative diagnosis of MDA and LEGH. Patients suspected of having LEGH may need to be treated with less aggressive methods.

Background: Endocervical adenocarcinomas of the usual type are etiologically related to infection with oncogenic human papillomaviruses (HPVs). These tumors are typically diffusely positive for p16 and carcinoembryonic antigen (CEA) immunostains. The goal of our study was to determine the HPV status and immunohistochemical profiles of unusual histologic subtypes of endocervical adenocarcinoma., Methods: The study consisted of a total of 26 cases of unusual subtypes including clear cell carcinoma (CCC, n=9), gastric-type adenocarcinoma (GAS, n=11), minimal deviation adenocarcinoma (MDA, n=3), mesonephric adenocarcinoma (MSN, n=1), serous adenocarcinoma (SER, n=1), and malignant mixed Müllerian tumor (n=1). In addition, 5 cases of usual-type endocervical adenocarcinoma (UEA) were included in the study as a control group. The cases were tested for HPV using SPF-10 PCR and LiPA assays, and immunostained for p16, HIK1083, hepatocyte nuclear factor 1-β, p53, CEA, estrogen receptor (ER), and progesterone receptor (PR)., Results: HPV DNA was not detected in any of the unusual adenocarcinoma subtypes, with the exception of a single case of SER in which HPV16 was detected. p16 positivity did not correlate with HPV status, as 42% of HPV-negative tumors showed patchy/diffuse p16 overexpression; however, p16 positivity was uncommon in GAS/MDA. HIK1083 positivity was limited to GAS and MDA, indicating relative specificity for tumors with gastric mucin expression. Hepatocyte nuclear factor 1-β was positive in the majority of CCCs and also in other tumor variants and in some UEA as well, indicating a lack of specificity for clear cell differentiation. CEA was consistently negative in CCCs and in a single MSN, but positive in GAS, MDA, SER, and UEA, suggesting that it may serve as a negative marker of clear cell differentiation. p53 was diffusely positive in almost half of the GAS cases, whereas UEA showed mostly negative staining and other variants showed focal staining. PR was negative in all variant cases and in all UEA. ER expression, although mostly negative, showed focal staining in a few variant cases and UEA., Conclusions: Unusual variants of endocervical adenocarcinoma are not related to HPV infection, with only rare exceptions, and p16 overexpression in non-UEA does not correlate with HPV status. Negative staining for PR and ER may serve as a general marker of endocervical neoplasia. GAS/MDA may be differentiated from all other adenocarcinomas with either positive HIK1083 stain or negative/focal p16 stain. Positive CEA stain differentiates GAS/MDA from CCC and negative PR and ER stains differentiate GAS/MDA from benign endocervical glands. CCC may be distinguished from all other adenocarcinomas, except MSN, with a negative CEA stain. Strong and diffuse p53 positivity in SER may be useful in differentiation from UEA. MSN may be identified with negative CEA, ER, and PR stains.

A subset of endocervical-type mucinous adenocarcinomas (ACs) of the uterine cervix exhibit a gastric phenotype and morphology, as reported in cases of minimal deviation AC in which the presence of human papillomavirus (HPV) has been rarely detected. To investigate the HPV-independent pathway of carcinogenesis in cases of gastric-type AC, we investigated the common high-risk HPV (hr-HPV) status in 52 nonsquamous cell carcinomas, using a PCR-based typing method and immunohistochemistry of p16INK4a (a cyclin-dependent kinase inhibitor that is overexpressed in both cancerous and precancerous cervical tissue, making it an ideal biomarker for cervical cancer cases). Using novel morphological criteria, seven of 52 (13.5%) carcinomas were designated as gastric-type ACs, all of which were negative for both hr-HPV DNA and p16INK4a. Nongastric-type ACs were frequently positive for both hr-HPV DNA (90%, 28/31) and p16INK4a (94%, 29/31) with adenosquamous and neuroendocrine carcinomas demonstrating the presence of hr-HPV DNA in 86% (6/7) and 83% (5/6) of cases, respectively. In these two types of carcinoma, 86% (6/7) and 100% (6/6) were positive for p16INK4a, respectively. Our data suggests that gastric-type AC appears to represent an oncogenic hr-HPV-independent neoplasm and therefore is a potential pitfall of HPV DNA testing and vaccination.

Gastrointestinal phenotype in cervical adenocarcinomas was examined by immunohistochemistry and correlated with morphologic features. Antibody panels included anti-MUC2, MUC6, CD10, chromogranin A (CGA) and HIK1083. In addition, expression of p16INK4, a cyclin-dependent kinase inhibitor which is expressed in a variety of high-risk HPV-related conditions, was studied. A total of 94 invasive adenocarcinomas including 20 minimal deviation adenocarcinomas (MDAs) and 72 adenocarcinomas in situ (AIS) were examined. MDAs were most frequently positive for HIK1083 and/or MUC6, two representative gastric markers, with a rate of 95%, followed by intestinal-type adenocarcinomas (IAs) with a rate of 85% whereas only 27% of 56 usual endocervical-type adenocarcinomas (UEAs) were positive. MUC2, a goblet cell marker, was positive in 85% and 25% of IAs and MDAs, respectively, while in only 14% of UEAs. CD10 was positive in 15% of IAs, indicating incomplete intestinal differentiation without a brush border in most of the cases. CGA-positive cells were frequently seen in MDAs and IAs with rates of 60% and 62%, respectively. Nuclear and cytoplasmic p16INK4 positivity was identified in 93% of UEAs, whereas 30% of MDAs were positive for p16INK4. Results in AISs were comparable to their invasive counterparts, but morphologically usual-type AISs identified in eight cases of MDA were frequently positive for HIK1083 (75%) and MUC6 (63%), and p16INK4. Of note was the existence of lobular endocervical glandular hyperplasia (LEGH) with atypical features including cytologic abnormalities, and/or papillary projection, which were identified in this study in pure form (n=3) or in association with MDAs (n=6), but not in cases of other types of adenocarcinomas. These observations indicate that gastrointestinal phenotype is frequently expressed in MDAs and IAs, and there seems to be a possible link between MDA, and LEGH and morphologically usual-type AIS with gastric immunophenotype in histogenesis. Frequent absence of p16INK4 expression in MDAs suggests a possibility that high-risk HPV does not play a crucial role in development of MDAs, in contrast to the majority of endocervical adenocarcinomas. p16INK4 immunohistochemistry appears to be a promising diagnostic tool, but pathologists should be aware of frequent negative staining in MDAs, which can be a source of erroneous diagnosis.