Clinical outcome in diagnostically ambiguous foci of 'gland crowding' in the endometrium

Lesions sub-diagnostic of endometrioid intra-epithelial neoplasia/atypical hyperplasia: value of morphology and immunohistochemistry in predicting neoplastic outcome

AIMS

Areas of gland crowding that do not fulfil diagnostic criteria of endometrioid intra-epithelial neoplasia (EIN) are often encountered in endometrial biopsies. In this study, we document the prevalence of neoplastic outcome in patients with these subdiagnostic lesions (SL) and assess the utility of morphological features and a three-marker immunohistochemistry panel (PAX2, PTEN, beta-catenin) to predict outcome.

METHODS AND RESULTS

Of 430 women with SL on endometrial sampling at Brigham and Women's Hospital between 2001 and 2021 with available follow-up biopsy, 72 (17%) had a neoplastic outcome (EIN or endometrioid carcinoma). Multilayered epithelium and mitoses in SL were statistically associated with a neoplastic outcome. Abnormal three-marker staining was observed in 93% (53 of 57) of SL with neoplastic outcome and 60% (37 of 62) of a control group with benign outcome. Among the 72 patients with neoplastic outcome, EIN/carcinoma tissue was available in 33; of these, 30 (91%) showed abnormal staining for one or more markers. Remarkably, in 84% of these cases the EIN/carcinoma had the aberrant expression seen in the preceding SL. Based on a prevalence of 17%, the positive and negative predictive values of abnormal staining in one or more markers were 24 and 97%, respectively.

CONCLUSIONS

The presence of SL warrants clinical surveillance and repeat sampling because it is followed by endometrioid neoplasia in a significant subset of patients. Normal three-marker staining identifies women with a very low risk of neoplastic outcome. Conversely, abnormal staining is frequent in SL with benign outcome leading to poor specificity and positive predictive value.

Glandular Crowdings in Endometrial Polyps: Clinical Follow-Up and Possible Worrisome Features

INTRODUCTION

Interpretation of changes and premalignant lesions in endometrial polyps can be challenging. We evaluated the clinical course of patients with focal gland crowdings in endometrial polyps via repeat biopsies and searched for possible morphological findings in the initial biopsy that may foresee a premalignant course.

METHODS

Specimens diagnosed as endometrial polyp and focal gland crowding in patients who had a repeat biopsy in a 1-year period were reexamined. Morphological findings in the initial biopsies were recorded. The group whose repeat biopsies were "premalignant or malignant" (Group 1), and the group with "benign" repeat biopsies (Group 2) were compared.

RESULTS

"Endometrial polyp and gland crowdings" was diagnosed in 115 specimens of which 38 patients had repeat biopsies. Among these 8 (21%) were diagnosed as "endometrial intraepithelial neoplasia (EIN)" (Group 1) and 30 (79%) as "benign" (Group 2). Morphological features in the initial biopsies were evaluated; PAX2 loss was 6 of 8 (75%) for Group 1 and 7 of 30 (23%) for Group 2 (P = .020), and altered epithelial cytological features were present in 5 of 8 (62%) versus 4 of 30 (13%) (P = .015), both significantly higher in Group 1. Dark intraluminal secretion, intraluminal histiocytes, intraglandular epithelial proliferation, and mean diameter of crowded gland areas were not statistically different between the 2 groups.

CONCLUSION

"Focal gland crowdings" in endometrial polyps do carry a risk of EIN in subsequent biopsies. We suggest that the loss/decrease of PAX2 and altered epithelial cytological features in these areas in the initial biopsy are indicative of a premalignant course.

Endometrioid Squamous Proliferations of the Endometrium Express Alpha-Methylacyl-CoA Racemase (P504s)

Squamous morular metaplasia is closely associated with endometrioid proliferative lesions such as endometrial intraepithelial neoplasia, whereas endometrioid adenocarcinoma may also demonstrate squamous differentiation (morular or nonmorular). Alpha-methylacyl-CoA racemase (AMACR; P504s) is an immunohistochemistry marker expressed in many tumors, including prostate adenocarcinoma, renal cell carcinoma, and in a subset of gynecologic carcinomas, predominantly of clear cell histology. In small biopsy samples, the distinction between cervical high-grade squamous intraepithelial lesions (HSILs) involving endocervical glands from endometrioid squamous proliferations can be challenging, given their anatomic vicinity and some degree of morphologic overlap. Following the observation of AMACR positivity by immunohistochemistry within squamous morules in an index case, 35 endometrial samples containing squamous morular metaplasia (25) and nonmorular squamous metaplasia (10), and 32 cases of cervical HSIL involving endocervical glands were stained with AMACR. The endometrial cohort consisted of 2 benign anovulatory endometrium, 7 endometrial polyps, 7 endometrial intraepithelial neoplasia, 4 atypical polypoid adenomyomas, and 15 endometrioid adenocarcinomas. Positive cases were scored as diffuse (≥50%) or focal (<50%). AMACR staining was present in 96.7% of endometrial squamous lesions, including 14 (93.3%) of endometrioid carcinomas, and in all cases of endometrial intraepithelial neoplasia, endometrial polyps, atypical polypoid adenomyomas, and anovulatory endometrium with squamous morular metaplasia or nonmorular squamous metaplasia. In comparison, only 2 cases (5.8%) of cervical HSIL demonstrated positivity for AMACR. In conclusion, AMACR can reliably differentiate the cervical versus endometrial origin of squamous lesions in small biopsy specimens.

Reliable Identification of Endometrial Precancers Through Combined Pax2, β-Catenin, and Pten Immunohistochemistry

The diagnosis of endometrial atypical hyperplasia/endometrioid intraepithelial neoplasia (AH/EIN) remains challenging and subjective in some cases, with variable histologic criteria and differences of opinion among gynecologic pathologists, potentially leading to under/overtreatment. There has been growing interest in the use of specific immunohistochemical markers as adjuncts in AH/EIN diagnosis. For example, the World Health Organization 2020 Classification specifies that loss of Pten, Pax2, or mismatch repair proteins are desirable diagnostic criteria. Other markers, most notably β-catenin and Arid1a, are also aberrantly expressed in some AH/EIN. However, the performance of some markers individually-and more importantly as a group-has not been rigorously explored, raising questions as to which marker(s) or combination(s) is the most effective in practice. Formalin-fixed paraffin-embedded tissue sections from AH/EIN cases (n=111) were analyzed by immunohistochemistry for 6 markers: Pax2, Pten, Mlh1, β-catenin, Arid1a, and p53. Aberrant expression was tabulated for each case and marker. An additional set of normal endometria (n=79) was also analyzed to define optimal diagnostic criteria for marker aberrance. The performance characteristics of each marker, the entire panel, and subsets thereof were quantitatively and statistically analyzed. In order of number of cases detected, the most frequently aberrant markers in AH/EIN were Pax2 (81.1% of cases), Pten (50.5%), β-catenin (47.7%), Arid1a (7.2%), Mlh1 (4.5%), and p53 (2.7%). The majority of cases showed aberrant expression of ≥2 markers. All 6 markers together identified 92.8% of cases. Arid1a, Mlh1, and p53 were robust and readily scored markers, but all cases showing aberrant expression of these 3 markers were also detected by Pax2, Pten, or β-catenin. A focused panel of only 3 markers (Pax2, Pten, and β-catenin) showed optimal performance characteristics as a diagnostic adjunct in the histopathologic diagnosis of AH/EIN. Use of this panel is practicable and robust, with at least 1 of the 3 markers being aberrant in 92.8% of AH/EIN.

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.

Benign and Premalignant Lesions of the Endometrium

In this review, we highlight the benign and premalignant lesions of the endometrium that the pathologist may encounter in daily practice. We begin by detailing our current understanding of excess estrogen in the progression of endometrial neoplasia. We outline the currently accepted terminology to be used when evaluating proliferative endometrial lesions, while highlighting their key features. Attention is then turned to the molecular underpinnings of neoplastic progression and how this can be exploited with immunohistochemical stains when appropriate. Finally, we discuss types of metaplasia and their associations, including so-called papillary proliferations of the endometrium.

Endometrial intraepithelial neoplasia

CONTEXT

Developed in conjunction with molecular and progression data, the sequence classification schema for endometrial intraepithelial neoplasia (EIN)/benign hyperplasia (BH) provides an easy to adopt and reproducible method for classification of endometrial biopsies.

OBJECTIVE

To review current data supporting the use of BH/EIN to classify endometrial biopsies, and to discuss the hormone-driven endometrial sequence from anovulation/disordered proliferative endometrium through BH and EIN and their diagnostic difficulty.

DATA SOURCES

A comprehensive review of EIN literature based on literature indexed by PubMed (National Library of Medicine) and Google Scholar.

CONCLUSIONS

The BH/EIN schema is gaining wider acceptance among pathologist and clinicians. The research leading to the EIN criteria is based on molecular and progression data. The BH/EIN schema has better reproducibility among pathologists, is intuitively easy to use, and requires understanding of endometrial physiology and neoplasia.

Utility of PAX2 as a marker for diagnosis of endometrial intraepithelial neoplasia

Diagnosis of endometrial intraepithelial neoplasia (EIN) requires learning new criteria. Two trainees rendered diagnoses based on biopsy findings, and then measured the effect of reviewing PAX2 on their interpretation. Fifty-two endometrial biopsy specimens diagnosed as having EIN were evaluated using EIN criteria. Background endometrial pattern, altered differentiation, and any features complicating diagnosis were noted. PAX2 stains were scored as confusing, helpful, or noncontributory. Fifty-two cases generated 104 passes; 82% were rediagnosed as EIN. The diagnosis was complicated because of altered differentiation (14%), EIN and background separation (13%), large lesions lacking background (11%), and secretory background (8%). PAX2 was most helpful in cases with secretory backgrounds and when EIN lacked adjacent normal tissue, and most confusing when scoring was ambiguous (14%). The diagnosis of EIN can be difficult when: (1) the lesion cannot be easily compared with background; (2) there is a confounding process; and (3) gland differentiation is altered. PAX2 can be of assistance in delimiting EIN lesions.

Endometrial intraepithelial neoplasia

Endometrial intraepithelial neoplasia (EIN) is a monoclonal premalignant endometrial glandular lesion that precedes the development of endometrioid-type endometrial adenocarcinoma. EIN arises through complex interactions involving the sequential accumulation of genetic damage in endometrial glands and the positive selective pressure of unopposed estrogen. Recent data have revealed a preclinical latent precursor lesion composed of mutated but morphologically nondescript glands that may persist for years in normal-appearing premenopausal cycling endometrium. This latent precursor shares many of the molecular features of EIN and endometrial adenocarcinoma, including frequent inactivation of both the tumor suppressor gene PTEN and the paired box-containing gene PAX2. Upon progression to EIN, the distinctive appearance of crowded and cytologically altered glands heralds a 45-fold increased risk of developing endometrial adenocarcinoma. To preserve the high predictability of EIN for concurrent/ subsequent adenocarcinoma, strict adherence to defined diagnostic criteria is essential. These criteria, as well as potential diagnostic pitfalls and their resolution, are discussed herein.