Immunohistochemical differences between mucinous and microglandular adenocarcinomas of the endometrium and benign endocervical epithelium

Molecular Analysis of HPV-independent Primary Endometrial Squamous Cell Carcinoma Reveals TP53 and CDKN2A Comutations : A Clinicopathologic Analysis With Re-evaluation of Diagnostic Criteria

Human papillomavirus (HPV)-independent primary endometrial squamous cell carcinoma (PESCC) is a rare but aggressive subtype of endometrial carcinoma for which little is known about the genomic characteristics. Traditional criteria have restricted the diagnosis of PESCC to cases without any cervical involvement. However, given that modern ancillary techniques can detect HPV and characteristic genetic alterations that should identify the more common mimics in the differential diagnosis, including endometrial endometrioid carcinoma with extensive squamous differentiation and HPV-associated primary cervical squamous cell carcinoma, those criteria may benefit from revision. To further characterize PESCC, we identified 5 cases of pure squamous cell carcinoma dominantly involving the endometrium that had the potential to be PESCC: 1 case involving only the endometrium and 4 cases with some involvement of the cervix. Clinicopathologic features were assessed and immunohistochemical analysis (p16, estrogen receptor, progesterone receptor, and p53), HPV RNA in situ hybridization (high-risk and low-risk cocktails and targeted probes for 16 and 18), and molecular studies were performed. All tumors showed aberrant/mutation-type p53 expression, were negative for estrogen receptor, progesterone receptor, and p16, and had no detectable HPV. Per whole-exome sequencing, 4 of the 5 tumors demonstrated comutations in TP53 and CDKN2A (p16). Four patients died of disease within 20 months (range, 1 to 20 mo; mean, 9 mo), and 1 patient had no evidence of disease at 38 months. PESCC represents a unique, clinically aggressive subtype of endometrial cancer with TP53 and CDKN2A comutations. This characteristic profile, which is similar to HPV-independent squamous cell carcinoma of the vulva, is distinct from endometrioid carcinoma with extensive squamous differentiation and HPV-associated primary cervical squamous cell carcinoma and can be used to distinguish PESCC from those mimics even when cervical involvement is present. Diagnostic criteria for PESCC should be relaxed to allow for cervical involvement when other pathologic features are consistent with, and ancillary techniques are supportive of classification as such.

Mucinous Proliferations of the Uterine Corpus: Comprehensive Appraisal of an Evolving Spectrum of Neoplasms

A variety of endometrial lesions may contain mucinous cells. Herein, the author reviews the literature on the classification and clinicopathologic significance of uterine corpus proliferations with a significant mucinous component, assesses the 2020 World Health Organization classification of such lesions, and presents a diagnostic framework. The key epithelial mucinous lesions include mucinous metaplasia, atypical mucinous glandular proliferation and mucinous carcinoma. Each of these categories are classifiable into "usual" and gastrointestinal subtypes, the latter being indicative of intestinal (presence of goblet cells) and/or gastric-type (abundant, pale eosinophilic or clear cytoplasm and well-defined cell borders) morphology. It has been proposed that at least focal expression of gastrointestinal immunohistochemical markers be required for all gastrointestinal type lesions, and for gastrointestinal type atypical mucinous glandular proliferation and carcinoma, minimality or absence of estrogen receptor expression, and the absence of an endometrioid component. Mucinous carcinomas of the usual type, in which >50% of the tumor is comprised of a mucinous component, are the most common. Morphologic subtypes include mucinous carcinoma with microglandular features and mucinous carcinoma with signet rings (signet ring carcinoma). Endometrioid carcinomas with a less than a 50% mucinous component are classified as endometrioid carcinoma with mucinous differentiation. Several studies have directly compared endometrioid and mucinous carcinomas, the latter presumably of the usual type, with respect to patient outcomes after treatment. All have found no difference in overall and disease free survival between these groups. However, three major studies have found mucinous carcinomas to be associated with a higher risk of lymph node metastases. Nineteen cases of mucinous carcinoma of the gastrointestinal type have been reported, and the limited data on their follow-up after primary treatment suggests that this subtype is more clinically aggressive and should accordingly be classified separately from mucinous carcinomas of the usual type. The morphologic spectrum of mucinous carcinoma of the gastrointestinal type is unclear and continues to evolve. Mucinous change, which may sometimes be extensive, may also be associated with papillary proliferation of the endometrium, adenomyoma of the endocervical type, atypical, and typical adenomyomas. In a curettage or biopsy, intestinal type mucinous epithelium may be indicative of any of the gastrointestinal lesions mentioned above, but may also represent samplings of uterine teratomas, yolk sac tumors, genital and extragenital adenocarcinomas with intestinal differentiation, or low-grade appendiceal mucinous neoplasms that secondarily involve the endometrium.

Microglandular hyperplasia-like mucinous adenocarcinoma of the endometrium: A rare case report

BACKGROUND

Microglandular hyperplasia (MGH) is a proliferation of endocervical glands, related to estrogen stimulation, mainly occurring in the reproductive age group. The differential diagnosis includes endometrial adenocarcinoma with MGH-like pattern (MGA), a distinction that may be particularly problematic in curettage specimen.

CASE SUMMARY

A 57-year-old, postmenopausal woman was admitted in our hospital for surgical treatment. She had been diagnosed with a uterine leiomyoma, after complaints of irregular vaginal bleeding. She underwent dilatation and curettage (D&C) and subsequent total abdominal hysterectomy with bilateral salpingo-oophorectomy. D&C were compatible with MGA. Histologically, a proliferation of small glands, without intervening stroma, with mucin production, accumulation of neutrophils in the gland lumen and stroma, mild nuclear atypia and rare mitoses, were seen. In the hysterectomy specimen, the endometrium was thickened, but without apparent tumor formation. On microscopic examination, a residual similar adenocarcinoma was seen in the isthmus and more conventional-of endometrioid and mucinous type, in the rest of the endometrium.

CONCLUSION

MGH-like proliferation with mild cytologic atypia, detected in the endometrial curettage specimen of a postmenopausal woman, should alert pathologists for MGA of the endometrium. VIM, p16, PAX-2, CD10 and CD34 may help in the differential diagnosis.

Utility of p63 and PTEN Staining in Distinguishing Cervical Microglandular Hyperplasia from Endometrial Endometrioid Carcinoma with Microglandular/Mucinous Features

Aims

Distinction between well‐differentiated endometrial carcinoma (EMCA) with microglandular/mucinous features and benign endocervical microglandular hyperplasia (MGH) can be a diagnostic challenge, especially when tissue is limited. The immunostains used to distinguish endocervical and endometrial carcinoma are less useful when the differential diagnosis is MGH. Here, we investigate the utility of p63 and phosphatase and tensin homologue (PTEN) to aid accurate classification.

Methods and results

Cases obtained from our pathology archives included 25 EMCA with mucinous/microglandular features, 26 MGH and nine atypical microglandular proliferations. Cases were assessed for glandular architecture, presence of mucinous and/or eosinophilic luminal secretions, subnuclear vacuoles, foamy histiocytes, inflammation, squamous metaplasia, cytological atypia and mitotic activity. The presence and pattern of immunohistochemical staining for p63 and PTEN was recorded. Microglandular proliferations with cytological atypia, mitotic activity, foamy histiocytes and complex glandular architecture were more commonly seen in EMCA, while small glands, bland nuclei and subnuclear vacuoles were enriched in MGH. All MGH cases displayed p63‐positive subcolumnar reserve cells and retained PTEN expression. Four EMCA cases showed non‐specific focal p63 staining either at the surface of the tumour or in areas of squamous differentiation. p63 and PTEN immunostains accurately predicted the final diagnosis for 3 atypical microglandular proliferation cases with follow‐up.

Conclusions

While there are morphological characteristics that differentiate EMCA and MGH, there is frequent overlap between these entities. Nonetheless, the pattern and extent of p63 and PTEN can aid accurate classification. Consistent p63‐positive subcolumnar reserve cells were seen only in MGH.

KRAS-mutated Uterine Endometrioid Carcinoma With Extensive Surface Changes Resulting in Striking Morphologic Mimicry of an Ovarian Serous Borderline Tumor

Surface epithelial changes involving endometrioid carcinomas of the uterine corpus mimicking papillary syncytial metaplasia or cervical microglandular hyperplasia are relatively common. There have been rare reports of surface epithelial changes in endometrioid carcinomas mimicking ovarian serous borderline tumor or low-grade serous carcinoma. We report an endometrioid carcinoma of the uterine corpus with striking morphologic mimicking of an ovarian serous borderline tumor with only a minimal amount of conventional endometrioid carcinoma. The tumor was diffusely positive for estrogen receptor, negative for WT1, and showed wild-type immunoreactivity with p53. Targeted sequencing revealed a KRAS mutation (G12V/D/A), but no BRAF mutation. This close mimicry of a serous borderline tumor by a uterine endometrioid carcinoma has not been emphasized in the literature and this case is unique because the features involved almost the entire neoplasm. In reporting this case, we review surface changes in endometrioid carcinomas of the uterine corpus.

Frequent promoter methylation of HOXD10 in endometrial carcinoma and its pathological significance

Homeobox D 10 (HOXD10) is important in cell differentiation and morphogenesis and serves as a tumor suppressor gene (TSG) in a number of malignancies. The present study investigated its promoter methylation status and association with the clinicopathological features of endometrial cancer (EC), and measured HOXD10 protein expression levels. EC samples (n=62), including 50 endometroid adenocarcinoma (EA) and 12 mucinous endometrial carcinoma samples (EC) and 70 non-cancerous samples were collected. All samples were evaluated for the methylation status of several TSGs, including HOXD10, using methylation-specific PCR. HOXD10 expression level was evaluated using immunohistochemistry. 5-Aza-2-deoxycytidine treatment was performed in the EC cell line Ishikawa to observe the change in HOXD10 expression levels. HOXD10 promoter methylation was more frequent in cancer samples (P<0.001). Downregulation of HOXD10 in EC samples was confirmed at the protein level using immunohistochemistry (P<0.001) and immunohistochemical staining was negatively associated with methylation status (P<0.05). Less HOXD10 protein was expressed in MEC compared with EA samples (P<0.001). The HOXD10 promoter was hypermethylated in both EA and MEC, causing decreased HOXD10 protein expression levels in EC cells. HOXD10 expression levels were partially reversed by 5-Aza-2-deoxycytidine treatment. The results of the present study demonstrated that epigenetic silencing of HOXD10 putatively contributed to the tumorigenesis of EA. Although there was no significant difference in HOXD10 methylation between EA and MEC, HOXD10 protein expression levels differed between these two diseases, indicating that it may be a useful protein biomarker for distinguishing between these two lesions.

Emerging relationships between papillary proliferation of the endometrium and endometrial carcinoma: evidence from an immunohistochemical and molecular analysis

Papillary proliferation of the endometrium (PPE) is an uncommon lesion that frequently shows mucinous metaplasia. PPE occasionally has concurrent or preceding endometrial hyperplasia and carcinomas, but there is little molecular evidence to support the relationships between PPEs and endometrial neoplasia. In this study, we analyzed the clinicopathological and immunohistochemical features in 30 PPEs (22 simple PPEs and 8 complex papillary hyperplasia (CPH)). Hotspot mutations of KRAS, PI3KCA, AKT1, PTEN (exons 3, 5, and 7), and ARID1A (exons 1 and 14) were detected by pyrosequencing or bidirectional Sanger sequencing. We found that endometrial hyperplasia and carcinoma were more common in CPHs (4/6, 66.7%) than in simple PPEs (4/21, 19.0%) (p < 0.05). Compared with the adjacent normal endometrium, PPEs frequently showed loss of PAX2 (56.7%) and PTEN (10%) expression, diffuse p16 expression (36.7%), decreased PR expression (84.3%), and lower Ki67 labeling index (median 1%, range 1-15%). Simple PPEs and CPHs had similar immunohistochemical features (p > 0.05). KRAS mutations were identified in 14 PPEs and 1 concurrent endometrial carcinoma. The prevalence of KRAS mutations was not statistically different between simple PPEs (10/21, 45.5%) and CPHs (4/8, 50%) (p > 0.05), but was higher in PPEs displaying mucinous metaplasia (12/24, 50%) than in those without (2/6, 33.3%) (p < 0.05). One simple PPE with a KRAS mutation had an AKT1 mutation. No PPEs demonstrated mutations in PI3KCA, PTEN, and ARID1A. In conclusion, both simple PPE and CPH share some common molecular alterations with endometrial neoplasia, in which, KRAS mutations might be a driver.

The diagnosis of mucinous lesions in endometrial samplings by gynaecological pathologists: an analysis of diagnostic reproducibility

The purpose of this study is to assess the reproducibility among gynaecological pathologists in their diagnosis of mucinous alterations in endometrial sampling specimens. Twenty-six cases were independently reviewed by four experienced gynaecological pathologists from four academic medical centres. Pathologists were asked to classify each case into one of four groups, including three World Health Organization (WHO)-recognised categories: (1) mucinous metaplasia; (2) atypical mucinous glandular proliferation; (3) carcinoma; and (4) 'other' (absence of a true mucinous alteration and/or an alteration of non-endometrial origin). The overall reproducibility was 'fair' (κ = 0.39). In an analytical scenario that established three clinically significant groups ('benign/non-neoplastic', 'atypical', and 'carcinoma') by redistributing all group 4 responses, the resultant kappa improved to 0.51 (moderate reproducibility). In another analysis with only two categories-'benign/non-neoplastic' versus 'atypical/carcinoma'-reproducibility was similarly moderate (κ = 0.46). However, with one exception, all cases that were ultimately diagnosed as carcinoma in a follow-up hysterectomy specimen, were classified as atypical or carcinoma in the preceding sampling. For 11 cases that were classified as either 'carcinoma' or 'atypical' by all observers, there was moderate reproducibility (κ = 0.53) in making that distinction, and none of a wide array of morphological features were found to significantly distinguish between these two categories. For five cases that all observers classified as either mucinous metaplasia or benign endocervix, reproducibility was substantial (κ = 0.67). In summary, gynaecological pathologists show moderate reproducibility in categorising mucinous alterations in endometrial sampling specimens as benign, atypical, or carcinomatous. They accurately classify as at least 'atypical' those cases that are ultimately diagnosed as carcinoma in the subsequent resection. Our findings suggest that there are indeed some mucinous alterations which have features that do not allow for reproducible assignment by pathologists into the WHO-recognised categories. In this subset of cases, there may be a need for better-defined diagnostic criteria and/or extra-morphological diagnostic tools.

[New features in the 2014 WHO classification of uterine neoplasms]

The 2014 World Health Organization (WHO) classification of uterine tumors revealed simplification of the classification by fusion of several entities and the introduction of novel entities. Among the multitude of alterations, the following are named: a simplified classification for precursor lesions of endometrial carcinoma now distinguishes between hyperplasia without atypia and atypical hyperplasia, the latter also known as endometrioid intraepithelial neoplasia (EIN). For endometrial carcinoma a differentiation is made between type 1 (endometrioid carcinoma with variants and mucinous carcinoma) and type 2 (serous and clear cell carcinoma). Besides a papillary architecture serous carcinomas may show solid and glandular features and TP53 immunohistochemistry with an "all or null pattern" assists in the diagnosis of serous carcinoma with ambiguous features. Neuroendocrine neoplasms are categorized in a similar way to the gastrointestinal tract into well differentiated neuroendocrine tumors and poorly differentiated neuroendocrine carcinomas (small cell and large cell types). Leiomyosarcomas of the uterus are typically high grade and characterized by marked nuclear atypia and lively mitotic activity. Low grade stromal neoplasms frequently show gene fusions, such as JAZF1/SUZ12. High grade endometrial stromal sarcoma is newly defined by cyclin D1 overexpression and the presence of the fusion gene YWHAE/FAM22 and must be distinguished from undifferentiated uterine sarcoma. Carcinosarcomas (malignant mixed Mullerian tumors MMMT) show biological and molecular similarities to high-grade carcinomas.

Pathology of Endometrial Carcinoma

On a clinicopathological and molecular level, two distinctive types of endometrial carcinoma, type I and type II, can be distinguished. Endometrioid carcinoma, the typical type I carcinoma, seems to develop through an estrogen-driven "adenoma carcinoma" pathway from atypical endometrial hyperplasia/endometrioid intraepithelial neoplasia (AEH/EIN). It is associated with elevated serum estrogen and high body mass index and expresses estrogen and progesterone receptors. They are mostly low grade and show a favorable prognosis. A subset progresses into high-grade carcinoma which is accompanied by loss of receptor expression and accumulation of TP53 mutations and behaves poorly. Other frequently altered genes in type I carcinomas are K-Ras, PTEN, and ß-catenin. Another frequent feature of type I carcinomas is microsatellite instability mainly caused by methylation of the MLH1 promoter. In contrast, the typical type II carcinoma, serous carcinoma, is not estrogen related since it usually occurs in a small uterus with atrophic endometrium. It is often associated with a flat putative precursor lesion called serous endometrial intraepithelial carcinoma (SEIC). The molecular pathogenesis of serous carcinoma seems to be driven by TP53 mutations, which are present in SEIC. Other molecular changes in serous carcinoma detectable by immunohistochemistry involve cyclin E and p16. Since many of the aforementioned molecular changes can be demonstrated by immunohistochemistry, they are useful ancillary diagnostic tools and may further contribute to a future molecular classification of endometrial carcinoma as recently suggested based on The Cancer Genome Atlas (TCGA) data.

How to approach the many faces of endometrioid carcinoma

This article reviews the salient features of variants of endometrioid carcinoma (ECa) that can pose a diagnostic challenge and/or are associated with unique clinicopathological findings. Variants with distinct architectural and cytologic features include the following: (1) ECa with a villoglandular pattern (tumor with finger-like papillae lined by bland cells with a tendency for vascular/lymphatic invasion and lymph node metastasis once this pattern is seen within the myoinvasive component); (2) papillary ECa of intermediate grade (grade 2) (tumor that can be mistaken for serous carcinoma, as it contains papillae showing slightly irregular contours, moderately atypical cells, and it is associated with vascular/lymphatic invasion/lymph node metastasis, but with common association with mucinous metaplasia, MELF (microcystic, elongated, and fragmented) pattern of invasion, and wild p53 expression); (3) ECa with non-villous papillae (tumor containing pseudopapillae within glands with bland-appearing cytology commonly associated with abortive squamous differentiation and otherwise not different from usual ECa); (4) ECa with microglandular-like pattern (tumor that mimics microglandular hyperplasia of the cervix, often lacking the typical appearance of microglandular hyperplasia and showing Ki-67 index >10%, strong CD10 expression, and negative PAX-2, p63, and CD34); and (5) ECa with sex cord-like formations and hyalinization (tumor with interconnected cords and nests of bland epithelioid and spindled cells that merge with a typical component of low-grade ECa, usually associated with squamous differentiation and hyalinization). This tumor should be distinguished from carcinosarcoma and, in contrast to the latter, it shows nuclear β-catenin expression, ER/PR and patchy p16 positivity, tends to present at a low stage, and has a favorable prognosis and (6) dedifferentiated ECa (tumor showing a low-grade ECa juxtaposed to an undifferentiated carcinoma-the latter characterized by variably sized monotonous, often non-cohesive cells with brisk mitotic activity and usually arranged in sheets). Undifferentiated carcinoma tends to be negative for PAX8 and ER/PR with variable expression of keratins and can be associated with microsatellite instability (may be part of Lynch syndrome). Variants with distinct cytological features include the following: (1) ECa with clear cells (tumors with clearing due to 'clear' (glycogenated) squamous cells, distinct vacuoles, or not otherwise specified. EC with clear cells should be distinguished from clear cell carcinoma by the absence of the variety of architectural patterns, lack of cuboidal/flattened/hobnail cells, and lack of degree of atypia usually detected in clear cell carcinoma. In addition, they are ER/PR positive and Napsin A and p504S negative in contrast to clear cell carcinoma); (2) ECa with spindle cells (tumor with transition from spindle cells to the glandular component of a low-grade ECa. The spindle cells are keratin, ER/PR, and patchy p16 positive and show wild-type p53 expression); (3) ECa with mucinous differentiation (this tumor can be mistaken for a cervical adenocarcinoma, as they have overlapping features. Expression of ER/PR and vimentin in the context of a negative or patchy p16 positivity and the absence of high-risk HPV allows a correct diagnosis).

Mucinous metaplasia of the endometrium: current concepts

OBJECTIVES

The objective of this review was to discuss the highly variable terminology describing mucinous metaplasia of the endometrium, histologic features and characteristic findings by special stains and immunohistochemistry, differential diagnostic challenges, current treatment and prognosis.

METHODS

A review of the literature was performed on mucinous metaplasia of the endometrium.

RESULTS

Mucinous metaplasia is an uncommon type of endometrial epithelial metaplasia, often associated with hyperestrogenic states or hormone replacement therapy. Histologic findings range from simple endocervical-type mucinous epithelium to architecturally complex mucinous proliferations. Mucinous metaplasia often presents a significant diagnostic challenge in endometrial biopsies and should be differentiated from endocervical microglandular hyperplasia, and mucinous or mixed mucinous and endometrioid carcinomas. Simple mucinous metaplasia is believed to have a low risk of associated carcinoma, whereas architecturally complex cases often show invasive malignancy on subsequent biopsy.

CONCLUSIONS

Complex mucinous proliferations should be managed with dilatation and curettage and repeat biopsy within 6months, and strong consideration should be given to a hysterectomy in persistent mucinous proliferations.

Diagnostic value and implications of vimentin expression in normal, reactive and neoplastic endocervical epithelium

AIMS

To assess vimentin immunoreactivity in normal, reactive and neoplastic endocervical epithelium, and compare the results with p16 protein, Ki-67 and bcl-2 expression.

METHODS

Sixty-two cervical biopsy specimens including normal endocervical epithelium, tubo-endometrioid metaplasia, adenocarcinoma in situ, stratified mucin producing intraepithelial lesions (SMILE), and invasive adenocarcinomas were stained immunohistochemically for vimentin and for p16 protein, Ki-67 and bcl-2. Twelve cases also included areas of high grade cervical intraepithelial neoplasia (CIN).

RESULTS

Normal endocervical epithelium usually showed subtle but distinct sub-nuclear and delicate lateral cell border vimentin expression while tubo-endometrioid metaplasia exhibited more diffuse cytoplasmic immunoreactivity. Usually adenocarcinoma in situ was completely negative and therefore vimentin staining sharply distinguished the benign and neoplastic epithelial elements. The SMILE lesions and high grade CIN were also vimentin negative in most cases. Most invasive adenocarcinomas were not stained but focal vimentin immunoreactivity was observed in 7/18 cases, and was restricted to small glands and infiltrating cell clusters at the deep (advancing) tumour margin.

CONCLUSIONS

Normal endocervical cells often exhibit vimentin staining, and this is increased in reactive and metaplastic situations, whereas adenocarcinoma in situ is usually completely negative. Therefore vimentin is a useful additional diagnostic marker in the assessment of problematic cervical glandular lesions. The localised re-expression of vimentin at the deep margin of some endocervical adenocarcinomas may be relevant to the process of tumour progression and invasion in these cases.