Endometrial glandular dysplasia: a putative precursor lesion of uterine papillary serous carcinoma. Part II: molecular features

Special Considerations in Classification and Workup of Endometrial Carcinomas

CONTEXT.—

A variety of uncommon malignant endometrial tumors can be challenging to diagnose because of overlapping morphology with more common entities. In some cases, immunohistochemical stains and/or molecular testing allow for more definitive diagnosis or prognostication.

OBJECTIVE.—

To review classic morphologic features of uncommon endometrial tumors, pathologic features of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in the diagnosis of these tumors.

DATA SOURCES.—

University of Michigan (Ann Arbor) cases and review of pertinent literature about each entity.

CONCLUSIONS.—

Although each of these uncommon endometrial tumors has morphologic mimics, key histologic features, immunohistochemical stains, and molecular testing allow for accurate classification.

Histopathologic diagnosis of endometrial precancers: Updates and future directions

Early detection of endometrial cancer, especially its precancers, remains a critical and evolving issue in patient management and the quest to decrease mortality due to endometrial cancer. Due to many factors such as specimen fragmentation, the confounding influence of endogenous or exogenous hormones, and variable or overlapping histologic features, identification of bona fide endometrial precancers and their reliable discrimination from benign mimics remains one of the most challenging areas in diagnostic pathology. At the same time, the diagnosis of endometrial precancer, or the presence of suspicious but subdiagnostic features in an endometrial biopsy, can lead to long clinical follow-up with multiple patient visits and serial endometrial sampling, emphasizing the need for accurate diagnosis. Our understanding of endometrial precancers and their diagnosis has improved due to systematic investigations into morphologic criteria, the molecular genetics of endometrial cancer and their precursors, the validation of novel biomarkers and their use in panels, and more recent methods such digital image analysis. Although precancers for both endometrioid and non-endometrioid carcinomas will be reviewed, emphasis will be placed on the former. We review these advances and their relevance to the histopathologic diagnosis of endometrial precancers, and the recently updated 2020 World Health Organization (WHO) Classification of Female Genital Tumors.

High-grade endometrial carcinomas: Morphologic spectrum and molecular classification

High-grade endometrial carcinoma (HGEC) is a heterogeneous group of tumors with various morphologic, genetic, and clinical characteristics. Morphologically, HGEC includes high-grade endometrioid carcinoma, serous carcinoma, clear cell carcinoma, undifferentiated/dedifferentiated carcinoma, and carcinosarcoma. The morphologic classification has been used for prognostication and treatment decisions. However, patient management based on morphologic classification is limited by suboptimal interobserver reproducibility, variable clinical outcomes observed within the same histotype, and frequent discordant histotyping/grading between biopsy and hysterectomy specimens. Recent studies from The Cancer Genome Atlas (TCGA) Research Network established four distinct molecular subtypes: POLE-ultramutated, microsatellite unstable, copy number high, and copy number low groups. Compared to histotyping, the TCGA molecular classification appears superior in risk stratification. The best prognosis is seen in the POLE-ultramutated group and the worst in copy number high group, while the prognosis in the microsatellite unstable and copy number low groups is in between. The TCGA subtyping is more reproducible and shows a better concordance between endometrial biopsy and resection specimens. It has now become apparent that the molecular classification can supplement histotyping in patient management. This article provides an overview of the pathologic diagnosis/differential diagnosis of HGEC and the TCGA classification of endometrial cancers, with the clinical significance and applications of TCGA classification briefly discussed when appropriate.

Proteomic Analysis of Pre-Invasive Serous Lesions of the Endometrium and Fallopian Tube Reveals Their Metastatic Potential

Serous endometrial cancer (SEC) and high grade serous ovarian cancer (HGSOC) are aggressive gynecological malignancies with high rates of metastasis and poor prognosis. Endometrial intraepithelial carcinoma (EIC), the precursor for SEC, and serous tubal intraepithelial carcinoma (STIC), believed to be the precursor lesion for HGSOC, can also be associated with intraabdominal spread. To provide insight into the etiology of these precancerous lesions and to explore the potential molecular mechanisms underlying their metastatic behavior, we performed a proteomic mass spectrometry analysis in a patient with synchronous EIC and STIC. Through histological and molecular identification of precancerous lesions followed by laser capture microdissection, we were able to identify over 450 proteins within the precancerous lesions and adjacent healthy tissue. The proteomic analysis of STIC and EIC showed remarkable overlap in the proteomic patterns, reflecting early neoplastic changes in proliferation, loss of polarity and attachment. Our proteomic analysis showed that both EIC and STIC, despite being regarded as premalignant lesions, have metastatic potential, which correlates with the common presentation of invasive serous gynecological malignancies at advanced stage.

Correlation of NQO1 and Nrf2 in Female Genital Tract Cancer and Their Precancerous Lesions (Cervix, Endometrium and Ovary)

Background

NAD (P) H/quinone oxidoreductase 1 (NQO1) is a metabolizing enzyme that detoxifies chemical stressors and antioxidants. Nuclear factor erythroid 2-related factor 2 (NrF2) is an important transcriptional activator involved in the cellular defense mechanisms against oxidative stress.

Methods

The immunohistochemical expression of NQO1 and Nrf2 in 80 cervical, 80 endometrial and 100 ovarian specimens with different lesions was studied. Then we study the relation of both NQO1 and Nrf2 expression and clinicopathological features of carcinoma cases.

Results

Immunohistochemical stain showed that NQO1 and Nrf2 were highly expressed in carcinoma compared with normal and precancerous lesions. Significant positive correlations were found between the mean expression of NQO1 and Nrf2 in different lesions. Moreover, there was significant correlation between the high level of NQO1 and Nrf2 expression and high tumor grade in cervical and endometrial carcinoma cases. Nrf2 expression was significant with advanced stage in endometrial and ovarian carcinomas.

Conclusions

NQO1 and Nrf2 might be new biomarkers for early diagnosis and prognostic evaluation as well as being targets for therapy in patients with tumors in female genital tract.

The Utility of Immunohistochemistry in the Differential Diagnosis of Gynecologic Disorders

Context

Immunohistochemistry has assumed an increasing role in the identification and characterization of gynecologic disorders including lesions with deceptively bland morphology, uncommon and underdiagnosed neoplasms, and neoplasms with specific genetic alterations associated with overexpression or loss of expression of specific proteins. The diagnostic accuracy has been significantly improved owing to the discovery and increasing experience with the tumor-associated biomarkers, and the increasing demand for precise tumor classification to assess suitability for the expanding therapeutic modalities including clinical trials.

Objective

To differentiate lesions of the gynecologic tract through the use of effective immunohistochemical panels.

Data Sources

Literature review and authors' personal practice experience.

Conclusions

The application of diagnostic and prognostic immunohistochemical panels has enabled pathologists to better guide therapeutic decisions and to better predict the clinical outcome. It is now well established that the use of ancillary testing, including immunohistochemistry, has a significant power in the identification, differentiation, and classification of reactive, premalignant, and malignant gynecologic disorders. This article discusses the utilities and pitfalls of the commonly used immunohistochemical markers in the context of overlapping morphologic features encountered in the uterus, ovaries, and fallopian tubes.

Evaluation of endometrial cytology prepared with the Becton Dickinson SurePath™ method: a pilot study by the Osaki Study Group

OBJECTIVE

To evaluate the sensitivity and specificity of the BD SurePath™ liquid-based Papanicolaou test for assessing the cytology of intrauterine endometrial samples according to newly devised cytological diagnostic criteria and a novel descriptive reporting format.

MATERIALS AND METHODS

One hundred and twenty-two endometrial samples were analyzed. All samples were obtained directly from the intrauterine cavity using the Uterobrush or Honest Super Brush. The samples used for the histological examination and cytological tests were collected simultaneously. Our study group devised new cytological diagnostic criteria for examining endometrial samples: the Osaki Study Group method. In this study, histological diagnosis was considered to be the gold standard for cytological diagnosis. A novel descriptive reporting format was also used.

RESULTS

Satisfactory cytological specimens were obtained in all cases. The sensitivity and specificity of the SurePath endometrial cytological examination method were 96.4 and 100%, respectively.

CONCLUSION

These results indicate that the SurePath method is acceptable for clinical use. Since the SurePath method seems to be easier and allows greater preparation standardization than the conventional method, coupling it with our newly devised cytological diagnostic criteria and descriptive reporting format might represent a reliable diagnostic method for assessing endometrial specimens.

[p53 suppresses type II endometrial carcinomas in mice and governs endometrial tumor aggressiveness in humans]

Type II endometrial carcinomas are a highly aggressive group of tumor subtypes that are frequently associated with inactivation of the TP53 tumor suppressor gene. We show that mice with endometrium-specific deletion of the Trp53 gene initially exhibited histological changes that are identical to known precursor lesions of type II endometrial carcinomas in humans and later developed carcinomas representing all type II subtypes. The mTORC1 signalling pathway was frequently activated in these precursor lesions and tumors, suggesting a genetic cooperation between this pathway and Trp53 deficiency in tumor initiation. Consistent with this idea, analyses of 521 human endometrial carcinomas identified frequent mTORC1 pathway activation in type I as well as type II endometrial carcinoma subtypes. The mTORC1 pathway activation and p53 expression or mutation status each independently predicted poor patient survival. We suggest that molecular alterations in p53 and the mTORC1 pathway play different roles in the initiation of the different endometrial cancer subtypes but combined p53 inactivation and mTORC1 pathway activation are unifying pathogenic features among histologically diverse subtypes of late stage aggressive endometrial tumors.

Novel MicroRNAs regulating proliferation and apoptosis in uterine papillary serous carcinomas

MicroRNAs (miRNAs) are endogenous, non-coding RNA transcripts that regulate gene expression. Here, we report 175 putative novel miRNAs identified in uterine cancers profiled by Next Generation Sequencing. Our data indicate that one of these putative miRNAs (BCM-173) is conserved across multiple species and is expressed at levels similar to known human miRNAs. Functionally, this miRNA promotes the growth and migration of uterine cancer cell lines by targeting vinculin and altering the distribution of focal adhesions. These results expand our insight into the repertoire of human miRNAs and identify novel pathways by which dysregulated miRNA expression promotes uterine cancer growth.

p53 suppresses type II endometrial carcinomas in mice and governs endometrial tumour aggressiveness in humans

Type II endometrial carcinomas are a highly aggressive group of tumour subtypes that are frequently associated with inactivation of the TP53 tumour suppressor gene. We show that mice with endometrium-specific deletion of Trp53 initially exhibited histological changes that are identical to known precursor lesions of type II endometrial carcinomas in humans and later developed carcinomas representing all type II subtypes. The mTORC1 signalling pathway was frequently activated in these precursor lesions and tumours, suggesting a genetic cooperation between this pathway and Trp53 deficiency in tumour initiation. Consistent with this idea, analyses of 521 human endometrial carcinomas identified frequent mTORC1 pathway activation in type I as well as type II endometrial carcinoma subtypes. mTORC1 pathway activation and p53 expression or mutation status each independently predicted poor patient survival. We suggest that molecular alterations in p53 and the mTORC1 pathway play different roles in the initiation of the different endometrial cancer subtypes, but that combined p53 inactivation and mTORC1 pathway activation are unifying pathogenic features among histologically diverse subtypes of late stage aggressive endometrial tumours.

The genomics and genetics of endometrial cancer

Most sporadic endometrial cancers (ECs) can be histologically classified as endometrioid, serous, or clear cell. Each histotype has a distinct natural history, clinical behavior, and genetic etiology. Endometrioid ECs have an overall favorable prognosis. They are typified by high frequency genomic alterations affecting PIK3CA, PIK3R1, PTEN, KRAS, FGFR2, ARID1A (BAF250a), and CTNNB1 (β-catenin), as well as epigenetic silencing of MLH1 resulting in microsatellite instability. Serous and clear cell ECs are clinically aggressive tumors that are rare at presentation but account for a disproportionate fraction of all endometrial cancer deaths. Serous ECs tend to be aneuploid and are typified by frequent genomic alterations affecting TP53 (p53), PPP2R1A, HER-2/ERBB2, PIK3CA, and PTEN; additionally, they display dysregulation of E-cadherin, p16, cyclin E, and BAF250a. The genetic etiology of clear cell ECs resembles that of serous ECs, but it remains relatively poorly defined. A detailed discussion of the characteristic patterns of genomic alterations that distinguish the three major histotypes of endometrial cancer is reviewed herein.

Molecular pathogenesis of endometrial and ovarian cancer

Pregnancy, breastfeeding, and oral contraceptive pill use interrupt menstrual cycles and reduce endometrial and ovarian cancer risk. This suggests the importance of turnover within Mullerian tissues, where the accumulation of mutations in p53 and PTEN has been correlated with number of cycles. The most common type of endometrial cancer (Type I) is endometrioid and molecular abnormalities include mutations in PTEN, KRAS and β-catenin. The Type I precursor is Endometrial Intraepithelial Neoplasia which displays PTEN defects. Type II endometrial cancer (whose precursors are less clear) includes serous and clear cell tumors and the most common alteration is p53 mutation. For ovarian cancer, histopathologic types parallel endometrial cancer and include serous, mucinous, endometrioid, and clear cell; some molecular features are also shared. The most frequent type of ovarian cancer is high grade serous that often displays p53 mutation and its precursor lesions may originate from normal-appearing fallopian tube epithelium that contains a p53 "signature". Mutations in KRAS, BRAF and PTEN are described in mucinous, endometrioid and low grade serous cancers and these may originate from ovarian cortical inclusion cysts. A consideration of molecular and other pathogenetic features, like epidemiology and histopathology, may provide a better understanding of endometrial and ovarian cancer.

Precursors of endometrial and ovarian carcinoma

This review discusses precursor lesions of endometrial and ovarian carcinoma with an emphasis on the unique molecular alterations that have led to the development of binary classification schemes for tumors of both the endometrium and ovary. While such a system is well established for endometrial carcinoma, only recently has a binary classification scheme been proposed for ovarian carcinoma. For both, the morphologic and molecular genetic-defining characteristics of their respective precursor lesions are described in detail. Furthermore, similarities and differences of the precursor lesions of specific tumors of these two genital tract organs are also addressed with a brief discussion of the clinical implications of their diagnosis.

Coexisting intraepithelial serous carcinomas of the endometrium and fallopian tube: frequency and potential significance

SUMMARY

Most serous adenocarcinomas involving both the endometrium and ovary are presumed to arise in the endometrium. Recently, serous tubal intraepithelial carcinoma (STIC) has been implicated in the pathogenesis of pelvic serous carcinoma. This study explored the potential relationship between STIC and uterine serous carcinoma. Twenty-two consecutive cases of serous carcinoma involving the endometrium were studied. In each case, fallopian tubes were submitted in toto according to the protocol for sectioning and extensive examination of the fimbriated end. Extent of the endometrial tumor and presence/absence of STIC were documented. Immunostaining for p53 and Wilms tumor-1 was performed on all cases with STIC. p53 mutation analysis was performed in a subset of matched STICs and endometrial tumors. Eleven cases showed concurrent endometrial and adnexal involvement, including 6 with endosalpingeal involvement; STIC was confirmed in 5. In all 5, the concurrent endometrial tumor was either noninvasive, or exhibited only superficial (<5%) myometrial invasion. In 2 cases, identical p53 mutations were shared by both tubal and endometrial lesions. This study shows that noninvasive, genetically related serous carcinomas may coexist in both tube and endometrium. As management of serous neoplasms is predicated on site of origin, we propose that the sectioning and extensively examining the fimbria protocol be applied to all endometrial serous carcinomas and that tumors with concurrent STIC be classified as a distinct subset of pelvic serous carcinomas pending a clearer understanding of tumor origin.

Molecular identification of "latent precancers" for endometrial serous carcinoma in benign-appearing endometrium

Alteration of p53 is an early event in the development of endometrial serous carcinoma (ESC). We have recently identified a group of benign-looking endometria with p53 overexpression, designated "p53 signatures." In this study, we investigated these p53 signatures and evaluated whether they represented "latent" precancers for ESC. The p53 signatures were specifically associated with ESC, frequently found in the benign-appearing endometrium adjacent to the ESC and only rarely in either the endometrium adjacent to endometrioid carcinomas or in non-cancerous uteri. Forty-two percent of the p53 signature samples showed at least one p53 gene mutation. There were eight ESC uteri with p53 signatures that revealed p53 gene mutations. In four (50%) of these cases, at least one identical p53 gene mutation was found in the signature glands, precancerous regions, and cancerous areas within the same uterus. We concluded that p53 gene mutations apparently precede the morphological changes in affected endometrial cells. The finding of identical p53 mutations in the p53 signatures, precancerous regions, and ESCs in a subset of the uteri provides further evidence of a probable shared lineage between these lesions and suggests that the epithelia that display these p53 signatures are likely latent ESC precancerous regions. These findings underscore the significance of the p53 signature as a target for further research in the early detection and prevention of ESC.

Evidence for a latent precursor (p53 signature) that may precede serous endometrial intraepithelial carcinoma

Both serous intraepithelial carcinoma and endometrial glandular dysplasia are associated with uterine serous carcinoma. Recently a candidate serous cancer precursor containing p53 mutations (p53 signature) was described in the fallopian tube. We analyzed normal and neoplastic endometrium for a similar entity. In total 10 endometrial polyps involved by intraepithelial and/or invasive carcinoma and 137 benign polyps were studied. All were stained for p53 and MIB-1. A subset of p53 signatures and carcinomas were analyzed for gamma-H2AX and p53 mutations. p53 signatures were identified in 7 of 10 cases intraepithelial carcinoma and were multicentric in 2. In one case, the signature was in continuity with intraepithelial carcinoma. Of 137 benign polyps (4%), 6 contained p53 signatures. The MIB-1 fraction in most signatures was less than 5%, and ranged from 50 to 90% in carcinomas. DNA damage (gamma-H2AX) was demonstrated in both p53 signatures and adjacent carcinomas but not in benign polyps. Shared identical p53 mutations were found in paired signatures and carcinomas in two of three cases analyzed, including one case with multiple signatures. In one, a coexistent invasive serous cancer was not found to contain a p53 mutation. In a third, a p53 signature and an invasive cancer harbored two different p53 mutations. This is the first description of p53 signatures adjacent to carcinoma, suggesting a role for this entity in the genesis of serous malignancy. The significance of p53 signatures in benign conditions (polyps) remains to be determined. The role of the p53 signature in early serous neoplasia is discussed.

Endometrial glandular dysplasia and endometrial intraepithelial neoplasia

PURPOSE OF REVIEW

In recent decades, progress has been made in defining endometrial precancers. Endometrial intraepithelial neoplasia has been widely accepted as a precancer of type I endometrial cancer, while endometrial glandular dysplasia is a newly described entity as a probable precancer of type II cancer. As endometrial intraepithelial neoplasia has been discussed more extensively in the literature, we focus more on the recent development of endometrial glandular dysplasia in this review.

RECENT FINDINGS

Serous endometrial intraepithelial carcinoma was previously considered as a putative precancer for endometrial serous carcinoma or uterine papillary serous carcinoma. It is now considered as an early form of endometrial serous carcinoma, however. Endometrial glandular dysplasia was found to be a better candidate for precancer for both endometrial serous and clear cell carcinomas, which meets almost all recently defined criteria for precancer. Biomarkers of p53 and IMP3 are helpful for the early detection of endometrial glandular dysplasia as well as type II endometrial cancers.

SUMMARY

Two types of endometrial cancers are derived from two different precancers. Type I endometrioid carcinoma develops from endometrial intraepithelial neoplasia, while type II derives most probably from endometrial glandular dysplasia. Recognition and correct detection of endometrial glandular dysplasia may deepen our understanding and improve prevention and clinical management for type II endometrial cancer.

Endometrial Glandular Dysplasia (EmGD): morphologically and biologically distinctive putative precursor lesions of Type II endometrial cancers

In this article, the authors briefly review the historical evolution of the various putative precursor lesions for Type II endometrial cancers, with an emphasis on the newly defined "Endometrial Glandular Dysplasia (EmGD)". The evidentiary basis for delineating serous EmGD as the most probable precursor lesions to endometrial serous carcinoma is reviewed in detail. An argument is advanced for the discontinuation of the term serous "endometrial intraepithelial carcinoma (EIC)" as a descriptor for a supposedly intraepithelial, precancerous lesion. Preliminary evidence is also presented that suggests that there is a morphologically recognizable "clear cell EmGD" that probably represents a precancerous lesion to endometrial clear cell carcinomas.

Occurrence of Endometrial Glandular Dysplasia Precedes Uterine Papillary Serous Carcinoma

Endometrial glandular dysplasia (EmGD) is a newly defined entity that is commonly and specifically associated with serous endometrial intraepithelial carcinoma and uterine papillary serous carcinoma (UPSC). Endometrial glandular dysplasia has been proposed as a true precancerous lesion of UPSC based on our recent studies showing morphological and molecular linkages between these 2 lesions. The present report is to examine if EmGD occurs before UPSC development and to define the period from the occurrence of EmGD to a full-blown UPSC by studying their clinicopathologic features in a retrospective setting. A total of 250 UPSC and 258 benign cases were used as initial study source. To identify if EmGD existed before the development of UPSC, we blindly reviewed all available endometrial biopsies from a period of 3 months or earlier before hysterectomies. These included an available pool of 27 biopsy specimens from UPSC group and 29 samples from benign control group. Any endometrial abnormalities, which morphologically qualified as EmGD as defined previously in preceding biopsies were recorded. Among all endometrial biopsies before hysterectomies, we morphologically identified a total of 10 EmGD cases; 9 (33%) of 27 were from UPSC group and 1 (3.5%) of 29 were from benign control group. All 10 morphologically diagnosed EmGD cases showed a high p53 staining score (>/=5) except 1 noncontributory from UPSC group and 1 from the benign control group with a score of 0. A high MIB-1 index score was seen in all EmGD cases, whereas low index was found in morphologically benign biopsies. The main purpose of this study is to report these retrospectively identified EmGD cases. The period from identifying EmGD to the presence of either a serous endometrial intraepithelial carcinoma or a full-blown UPSC ranged from 16 to 98 months with an average of 33 months. We conclude that occurrence of EmGD precedes the development of UPSC. The findings support our recently proposed UPSC development model, in which EmGD is likely to be a precursor lesion of UPSC. Further studies are needed to address issues in regard to molecular and cellular mechanisms, reversibility, risk of UPSC development, and clinical management of EmGD.

Precursors of Endometrial Clear Cell Carcinoma

The recognition of morphologically identifiable lesions which may confer an increased risk for subsequent development of an invasive malignancy offers an opportunity to investigate and better understand the molecular-genetic etiopathogenesis of the well-developed tumor, and potentially, to administer a therapeutic intervention before its development. In contrast to uterine endometrioid and serous carcinomas, very little is known about the potential precursor lesions of endometrial clear cell carcinoma (ECCC). In our routine practice, we have noted the presence of a spectrum of atypical glandular changes in the endometria adjacent to ECCC or endometrial carcinomas with a clear cell component, which on the basis of current criteria, would not qualify for any specific designation. We hypothesize that these lesions represent the earliest morphologically recognizable precursor lesions of ECCC and systematically characterize their clinicopathologic features herein. Thirty archived cases of pure ECCC (n=14) or mixed endometrial carcinomas with a >10% clear cell component (n=16) were retrieved and the "normal" endometria adjacent to the malignancies were evaluated in detail. Thirty-eight benign uteri and 30 uteri with classic endometrial endometrioid carcinoma (EEC) served as controls. All cases were reviewed in a blinded fashion. Putative precursor lesions (PPL) were searched for and identified microscopically. The lesions were typically isolated glands or surface epithelium (within an otherwise normal endometrial region) that displayed cytoplasmic clarity and/or eosinophilia with varying degrees of nuclear atypia. Twenty-seven (90%) of the 30 cases had at least 1 PPL. In contrast, PPL were identified neither in the benign uteri nor in endometrioid carcinoma control groups (P<0.001). A total of 67 foci of PPL were identified in the 27 cases with an average of 2.5 foci per case. The immunohistochemical expression of p53, mib-1, estrogen receptor (ERs), and progesterone receptor in the benign endometria, ECCC, and the PPL were evaluated on all 27 cases. The mean p53 scores for the benign endometria, PPL, and ECCC were 0, 4.5, and 6.2, respectively. Parallel values for mib-1 were 15%, 45%, and 63%. ER/progesterone receptor indices for benign endometria, PPL, and carcinoma were 90/80, 21.52/4.61, and 11/4, respectively. The PPL described herein have a morphologic and immunophenotypic profile which seems to be distinct from both the benign endometria in which they reside and the adjacent areas of ECCC. The high frequency of association of these lesions with ECCC, their frequent occurrence as isolated lesions within otherwise "benign-appearing" endometria, and their continuous spectrum of nuclear atypia from minimum (grade 1, cytologic atypia falls short of ECCC cells) to maximum (grade 3, cytologically identical to ECCC cells), argues in favor of our hypothesis that these may represent precursor lesions of ECCC. Further studies are required to conclusively define the nature of these lesions. However, such studies can only be performed if diagnostic surgical pathologists recognize, highlight, and segregate these lesions for further analysis.