Endometrial Gastric (Gastrointestinal)-type Mucinous Lesions: Report of a Series Illustrating the Spectrum of Benign and Malignant Lesions

Diagnosis and Risk Stratification of Ovarian Mucinous Neoplasms: Pattern of Invasion, Immunohistochemistry, and Molecular Diagnostics

Ovarian mucinous tumors are subclassified in multiple categories. Recent studies have highlighted issues in interobserver reproducibility. This review will focus on some new developments including criteria and ancillary tests that may help to improve interobserver reproducibility at clinically important thresholds. These issues include proposals for a separate terminology of teratoma-associated ovarian mucinous neoplasms, the role of TP53 immunohistochemistry in distinction of crowded mucinous borderline tumors and expansile mucinous carcinomas as well as the assignment of the infiltrative pattern of invasion, which recently has been validated as important prognostic factor even in low stage mucinous ovarian carcinoma.

Characterization of gastric/gastrointestinal-like immunophenotypes in endometrial endometrioid adenocarcinomas, including endometrioid adenocarcinomas with mucinous differentiation

Endometrial mucinous carcinoma of the gastric [gastrointestinal] type (MCG) is a rare, possibly aggressive subtype of endometrial cancer that should be distinguished from its potential mimics, including endometrioid carcinoma (EEC). Herein, we assess the frequency of gastric and gastrointestinal immunophenotypes in EEC without any discernible gastric/gastrointestinal-type morphology. Immunohistochemical analyses for KRT(CK)7, KRT20, CDX2, ER, SATB2, MUC6, PAX8, and HIK1083 were performed on 81 EEC, inclusive of consecutively archived low grade [with (n = 22) and without (n = 47) mucinous differentiation] and high grade (n = 12) cases. None displayed gastric-type morphology or goblet cells. Expression levels were semi-quantified as H-scores (combining intensity and extent of staining) on a standardized 0-300 scale. Among the gastric/gastrointestinal-type markers, 56%, 62%, 23%, 25%, and 0% of cases expressed MUC6, CDX2, KRT20, SATB2, and HIK1083 respectively. The expression levels for positive cases were generally limited, with average H-scores being 49.5 [range 1-250] for MUC6, 33.7 [1-285] for CDX2, 24.0 [1-270] for CK20, and 30.5 [2-220] for SATB2. Ten (12.35%) cases showed high expression (H ≥ 200) of at least 1 gastric/gastrointestinal-type marker, including 1, 2, 2 and 6 cases that were high positive for KRT20, SATB2, CDX2 and MUC6 respectively. Immunoreactive foci were generally indistinguishable from background at the morphologic level. There was no statistically significant correlation between the expression of any of the gastric/gastrointestinal-type markers and ER, KRT7 or PAX8 expression. In summary, gastric/gastrointestinal-type proteins are not uncommonly expressed at low levels in EEC. As such, positivity for these markers cannot be the sole basis for distinguishing EEC from MCG.

Pericardial effusion: Unusual immunohistochemical expression

Endometrial Gastric‐type Carcinoma is a rare disease, especially in cytology. A 65‐year‐old woman was admitted to the hospital due to intermittent chest tightness with dyspnoea. The chest CT showed a soft tissue shadow of the left lung with bronchial occlusion and pericardial effusion. What was her diagnosis?

Tongue Metastasis of Mucinous Colorectal Adenocarcinoma: Report of a Rare Case

Metastases in the oral and maxillofacial region, particularly in soft tissues, are exceedingly rare. Such metastases can present as swelling in older individuals, especially in the tongue and gingiva. Furthermore, colorectal metastases at this site are commonly found in the mandible and gingiva and usually share the same morphology as the primary tumor. Herein, we report the case of a 61-year-old woman with a metastatic nodule in the tongue covered by normal mucosa. The clinical, histopathological, and immunohistochemical findings were essential for the final diagnosis of colorectal metastasis, consistent with adenocarcinoma with mucinous differentiation and intestinal phenotype. Metastases of colorectal adenocarcinoma to the tongue are rare but should be included in the differential diagnosis of nodular lesions at this site. The diagnosis can therefore be made based on meticulous clinical and histopathological examination complemented by immunohistochemistry.

Low-grade endometrial endometrioid carcinoma of the p53-abnormal group: case presentation and diagnostic issues

P53-abnormal endometrial carcinomas are high-grade and aggressive tumors which should be treated with chemo-/radiotherapy. In low-grade endometrioid carcinoma (LGEC), abnormal expression of p53 is an exceptional finding and is typically accompanied by patchy p16 positivity and diffuse hormone receptor expression.

Herein, we report a case of LGEC exhibiting both p53 and p16 overexpression, highlighting the diagnostic pitfalls related to such phenotype.

A 60-year-old woman underwent hysterectomy and bilateral salpingo-oophorectomy with pelvic lymphadenectomy due to a deeply myoinvasive endometrial mass. The tumor showed glandular architecture, low-grade nuclei and glandular differentiation. Focal lymphovascular space invasion and no lymph node metastases were observed. Immunohistochemically, the tumor showed p53 overexpression, p16 block-type positivity, diffuse hormone receptors positivity and retained mismatch repair proteins expression. No POLE mutations were identified. A diagnosis of p53-abnormal LGEC was eventually made.

A glandular neoplasm with p53 and/or p16-overexpression on endometrial biopsy specimens may raise the concern of other entities such as serous carcinoma, HPV-related endocervical adenocarcinoma, and gastric-type adenocarcinoma. An immunohistochemical panel including hormone receptors, p53, p16 and mismatch repair proteins appears necessary for an accurate diagnosis of uterine adenocarcinomas.

The spectrum of oestrogen receptor expression in endometrial carcinomas of no specific molecular profile

AIMS

Decreased oestrogen receptor (ER) expression is a marker of poor prognosis in endometrial carcinomas (EC) of no specific molecular profile (NSMP), but the optimal cut-off to separate high-risk 'low ER' versus low-risk 'high ER' expression has not been defined. Here we characterised the distribution of ER staining in a cohort of ECs.

METHODS AND RESULTS

Biopsy specimens from 120 cases of NSMP EC were stained for ER and assigned an Allred score. In 66 additional cases ER staining of matched biopsy and hysterectomy were compared. Twelve of 120 tumours had an Allred score of 0-3, including three endometrioid carcinomas (EEA) (one G1, two G3), four clear cell carcinomas (CCC), two mesonephric-like adenocarcinoma (MLA) and one each of: gastric-type adenocarcinoma, carcinosarcoma and endometrial carcinoma NOS. Three had Allred scores of 4-5: two MLA and one high-grade carcinoma with yolk sac differentiation. Five had Allred scores of 6: four EEA (one G1, one G2, two G3) and one mixed clear cell and endometrioid carcinoma. The remaining 100 tumours with Allred scores ≥ 7 were all EEA (66 G1, 28 G2, five G3 and one grade unknown). Comparing the biopsy versus hysterectomy ER staining (n = 66), the results were within a single Allred score point, except two cases with strong diffuse expression in the biopsy (Allred 8) and moderate expression in the hysterectomy (Allred 5).

CONCLUSIONS

Most NSMP ECs (> 80%) show high ER expression (Allred score ≥ 7). All non-endometrioid carcinomas and a few endometrioid carcinomas had lower ER expression (Allred score ≤ 6) or were completely negative.

High-grade Endometrial Carcinoma With Serous and Colorectal Carcinoma-like Components: Unique Morphology in Correlation With Immunohistochemical and Molecular Findings

Endometrial carcinoma with intestinal differentiation/colorectal carcinoma-like (CRC-like) features is rare with few cases reported to date. Those described are mainly endometrioid carcinomas with intestinal differentiation. We report a case of high-grade endometrial carcinoma with serous and intestinal/CRC-like components. The gross, histologic, immunohistochemical, and molecular features are described for both components of the tumor in the initial diagnostic biopsy and subsequent resection specimen. The diagnosis of primary endometrial carcinoma with serous and CRC-like components is supported by immunohistochemical and molecular findings, as well as clinical workup. The rarity of this phenomenon poses diagnostic challenges. In addition, the literature is reviewed with specific emphasis on the molecular and pathologic features of mixed endometrial carcinomas, including those with intestinal/CRC-like features.

Gastric-type glandular lesions of the female genital tract excluding the cervix: emerging pathological entities

In the last two decades or so, a spectrum of benign, premalignant and malignant cervical glandular lesions exhibiting gastric differentiation has been described, with gastric-type adenocarcinoma representing the most common human papillomavirus (HPV)-independent cervical adenocarcinoma. More recently, limited literature has reported a variety of gastric-type glandular lesions at other sites within the female genital tract and, as in the cervix (the most common site for these lesions), a spectrum of benign, premalignant and malignant lesions has been proposed. We provide an update and review of the emerging spectrum of gastric-type glandular lesions at female genital tract sites other than the cervix. In the endometrium, putative gastric-type glandular lesions include mucinous metaplasia of gastric-type, atypical mucinous proliferation of gastric-type and gastric-type adenocarcinoma. Similarly in the vagina, gastric-type adenosis, atypical adenosis and adenocarcinoma have been described. There have also been occasional reports of gastric-type lesions involving the ovary and fallopian tube. We provide guidance on how to recognise gastric-type lesions morphologically and immunophenotypically and stress that sometimes these lesions occur at more than one site within the female genital tract (synchronous/multifocal gastric-type lesions of the female genital tract), sometimes in association with Peutz-Jeghers syndrome.

Molecular features for timely cancer diagnosis and treatment - tumors of the ovary, fallopian tube and endometrium

Gynecologic pathology has moved, within only a few years, from being a diagnostic area devoid of molecular testing into a diagnostic discipline in which such analyses are becoming routine. The direct relevance of molecular characterization to the choice of treatment of patients with carcinomas originating in both the uterus and adnexae makes it likely that such testing will only expand along with our understanding of the molecular make-up of these tumors. As a consequence, gynecologic pathologists have become an integral part of patient management, rather than lab personnel providing external services.In parallel, molecular testing is expanding as a tool for diagnosing rare tumors affecting these organs, including soft tissue tumors, sex cord-stromal tumors and germ cell tumors, as well as other rare entities. Increased knowledge in this area bears directly on the ability to diagnose these tumors in a reproducible manner, as well as recognize and consult on genetic diseases. Hopefully, despite the inherent difficulty in studying rare cancers, it will also translate into new therapeutic options for the malignant ones among these rare cancers.

Practical Updates and Diagnostic Challenges in Endometrial Carcinoma

CONTEXT.—

Clinical management of endometrial carcinoma largely depends on the morphologic parameters ascertained based on the pathologic evaluation of surgical resection specimens. However, there are numerous controversial and nonstandardized aspects of both the macroscopic and microscopic assessment of surgical specimens, including grossing, adequate sampling, diagnosis, staging, reporting, and ancillary testing.

OBJECTIVE.—

To provide a comprehensive practical review of standardized grossing, key morphologic findings for reporting and staging, and diagnostic and prognostic use of ancillary testing in endometrial carcinomas.

DATA SOURCES.—

The existing literature, recommendations of the International Society of Gynecological Pathologists, and specialty consensus guidelines.

CONCLUSIONS.—

This review article summarizes important aspects of the grossing and sampling of surgical resection specimens for microscopic examination, key morphologic parameters that are required for reporting and staging, and morphologic features and immunoprofiles helpful in the differential diagnosis of low-grade and high-grade endometrial carcinomas, as well as the current status of the molecular classification of endometrial carcinoma and human epidermal growth factor receptor 2 testing in serous carcinoma. The information presented herein can be helpful in overcoming diagnostic challenges and issues related to the pathology reporting of endometrial carcinoma to practicing anatomic pathologists.

Updates in the Use of Immunohistochemical Stains in Breast and Gynecologic Pathology

CONTEXT.—

The use of immunohistochemical stains in breast and gynecologic pathology has become increasingly complex, with various diagnostic, prognostic, and predictive applications.

OBJECTIVE.—

To provide an update and review of immunohistochemical stains used in the practice of breast and gynecologic pathology. Established and new entities are reviewed, with descriptions of histomorphology and immunohistochemical staining patterns and discussion of interpretive pitfalls.

DATA SOURCES.—

Data were obtained from review of the English-language literature and firsthand experience of the authors in breast and gynecologic pathology.

CONCLUSIONS.—

Many entities in breast and gynecologic pathology benefit from evaluation with various immunohistochemical stains. These studies not only aid in the diagnosis and staging of tumors but also can provide prognostic and predictive information. Updated guidelines for recommended ancillary studies such as mismatch repair, p53, and human epidermal growth factor receptor 2 (HER2) studies in endometrium, as well as estrogen and progesterone receptors and HER2 in breast, are discussed. Finally, the use and interpretation of established and novel immunohistochemical stains are discussed in various breast and gynecologic malignancies.

Recent Advances in the Classification of Gynecological Tract Tumors: Updates From the 5th Edition of the World Health Organization "Blue Book"

CONTEXT.—

The World Health Organization Classification of Tumours: Female Genital Tract Tumors, 5th edition, published in September 2020, comes 6 years after the 4th edition, and reflects the monumental leaps made in knowledge about the biology of gynecological tumors. Major changes include revised criteria for the assignment of the site of origin of ovarian and fallopian tube tumors, a revision in the classification of squamous and glandular lesions of the lower genital tract based on human papillomavirus association, and an entire chapter devoted to genetic tumor syndromes. This article highlights the changes in the 5th edition relative to the 4th edition, with a focus on areas of value to routine clinical practice.

OBJECTIVE.—

To provide a comprehensive update on the World Health Organization classification of gynecological tumors, highlighting in particular updated diagnostic criteria and terminology.

DATA SOURCES.—

The 4th and 5th editions of the World Health Organization Classification of Tumours.

CONCLUSIONS.—

The World Health Organization has made several changes in the 5th edition of the update on female genital tumors. Awareness of the changes is needed for pathologists' translation into contemporary practice.

Intestinal‑type mucinous carcinoma of the endometrium showing a polypoidal exophytic form: A case report

Although endometrial cancer is a common malignancy in women, rare histological subtypes can pose diagnostic challenges. Primary endometrial intestinal-type mucinous carcinoma is a newly recognized subtype of endometrial cancer that differs from Müllerian-type endometrial mucinous carcinoma. The present case report documents a rare case of intestinal-type mucinous carcinoma of the endometrium showing a polypoidal exophytic form. The patient, an 80-year-old female, was incidentally diagnosed with a uterine tumor during a follow-up for vulvar Paget's disease. Clinical and imaging examinations revealed a localized mass within the uterine cavity. Hysteroscopy and subsequent histological examination confirmed the presence of intestinal-type mucinous carcinoma of the endometrium. Microscopically, the tumor displayed adenocarcinoma containing an intestinal-type glandular epithelium with mild nuclear atypia. It stained positive for the gastrointestinal markers mucin 2 and caudal type homeobox 2, and stained negatively for estrogen receptor α. The patient underwent surgery and adjuvant chemotherapy, with no evidence of recurrence at the latest follow-up 6 months after surgery. Endometrial intestinal-type mucinous carcinoma is a rare histological subtype of endometrial cancer. Differential diagnoses include Müllerian-type endometrial mucinous carcinoma, endocervical adenocarcinoma, metastasis from gastrointestinal tract adenocarcinoma and non-neoplastic gastric/intestinal metaplasia. However, the prognosis of endometrial intestinal-type mucinous carcinoma remains unclear due to limited reported cases. Existing evidence suggests a poorer prognosis compared with classical mucinous carcinomas of the endometrium. The present case, which is characterized by a polypoidal exophytic tumor without myometrial invasion, showed a favorable outcome. Further documentation and characterization of the aforementioned rare malignancy are necessary to enhance the understanding of its clinical physiology and outcomes. The present case report highlights the diagnostic challenges associated with intestinal-type mucinous endometrial carcinoma. The inclusion of this type of malignancy in the latest World Health Organization classification emphasizes the need for further comprehensive studies and case reports to expand the current knowledge on this rare histological subtype.

Gastric (gastrointestinal)-type endometrial adenocarcinoma presenting as a solitary endometrial polyp: a case report and literature review on a novel and potentially aggressive endometrial cancer histotype

Gastric-type carcinoma of the endometrium is a rare endometrial cancer histotype, recently introduced in the 2020 WHO classification of the female genital tract tumors. Clinico-pathological features, as well as treatment strategies for this rare histotype, are not fully defined. We herein present an unusual case of endometrial carcinoma with mucinous features arising in a 58-year-old menopausal woman. Morphological features of the present case as well as immunohistochemical profile were consistent with gastrointestinal differentiation. Therefore, after clinical and imaging studies ruled out the possibility of a metastatic origin, a final diagnosis of gastric-type carcinoma of the endometrium was rendered.

Mixed Ovarian Neoplasms With Gastrointestinal-type Mucinous and Mullerian Epithelial Components: A Rare Group of Tumors Demonstrating the Phenotypic Plasticity of the Mullerian Epithelial Cell

Primary mucinous ovarian neoplasms, gastrointestinal-type (GI-type), are composed of mucin-producing tumor cells resembling intestinal goblet cells or gastric foveolar epithelium. In contrast to seromucinous tumors, which exhibit endocervical-type mucinous differentiation and are thought to be derived from endometriosis, the cell/tissue-of-origin of most GI-type mucinous ovarian tumors is unknown. We identified 8 GI-type mucinous ovarian tumors (cystadenomas, n=4; borderline tumor/carcinoma, n=4) with spatially distinct areas that showed morphologic features of Mullerian-type epithelial differentiation (ciliated cells or endometrioid-type glands). Immunohistochemistry for cell lineage markers and Alcian blue (pH 2.5)/Periodic Acid-Schiff staining were performed. Morphologically distinct components were isolated by microdissection, from which extracted DNA was analyzed by targeted next-generation sequencing. In all cases, immunohistochemistry demonstrated mucin-producing cells to be positive for at least one GI marker (CK20 or CDX2), while areas with morphologic features of Mullerian differentiation were positive for PAX8, ER and/or PR, and lacked expression of CK20 and CDX2; CK7 was strongly and diffusely positive in all tumor cells. Tumor cells with a gastric-type phenotype produced neutral mucin, while acidic mucin was present within intestinal-type goblet cells. Targeted sequencing revealed ARID1A mutations in all mixed borderline tumors/carcinomas (n=4); other recurrent genetic alterations included KRAS (n=2) and TP53 mutations (n=2). Shared mutations were present in paired Mullerian and GI-type mucinous tumor components in 4 mixed borderline tumors/carcinomas, with more shared mutations between components than private mutations specific to each component. All mixed borderline tumors/carcinomas were associated with endometriosis (n=3) or Mullerian inclusion cysts (n=1); mutation or loss of ARID1A expression was seen in these putative precursor lesions in 2 cases. Hence, ovarian neoplasms composed of clonally related GI-type mucinous and Mullerian-type epithelial components harbor ARID1A mutations and are frequently associated with endometriosis. The existence of a Mullerian stem/progenitor cell with the capacity to differentiate toward cell lineages within the GI-tract may be involved in the pathogenesis of at least a subset of GI-type mucinous ovarian neoplasms.

Primary endometrial gastric (gastro-intestinal)-type carcinoma: A practical approach

The latest WHO classification of the female genital tract tumors introduces a new type of carcinoma: the primary gastric-type (or gastro-intestinal type) carcinoma of the endometrium. This type of neoplasm tends to have a poor outcome, making its correct diagnostic important. As little is known about this entity and given its quite challenging diagnosis, we aim to review existing data about it and propose a practical diagnostic approach. There are currently 11 cases published in 8 articles fitting the precise definition of a primary gastric-type carcinoma of the endometrium. Three main differential diagnoses must be excluded before considering this tumor: endometrioid adenocarcinoma with mucinous (Müllerian-type) differentiation, endocervical primary, and gastro-intestinal primary. Morphological aspects of this tumor can be heterogeneous and confusing; in this context, immunochemistry can be helpful to highlight the gastric or intestinal differentiation, but also to eliminate a mucinous endometrioid adenocarcinoma of Müllerian-type, by the constant negativity of estrogen receptors. A metastasis of a primary gastro-intestinal tract carcinoma must also be excluded by clinical, endoscopic and imaging work-up. Finally, an endometrial extension of a primary endocervical gastric-type carcinoma should be ruled out by complete sampling of the cervix. Intestinal type endocervical adenocarcinoma is easier to eliminate since this is an HPV-associated neoplasm.

Data Set for the Reporting of Endometrial Cancer: Recommendations From the International Collaboration on Cancer Reporting (ICCR)

Endometrial cancer is one of the most common cancers among women. The International Collaboration on Cancer Reporting (ICCR) developed a standardized endometrial cancer data set in 2011, which provided detailed recommendations for the reporting of resection specimens of these neoplasms. A new data set has been developed, which incorporates the updated 2020 World Health Organization Classification of Female Genital Tumors, the Cancer Genome Atlas (TCGA) molecular classification of endometrial cancers, and other major advances in endometrial cancer reporting, all of which necessitated a major revision of the data set. This updated data set has been produced by a panel of expert pathologists and an expert clinician and has been subject to international open consultation. The data set includes core elements which are unanimously agreed upon as essential for cancer diagnosis, clinical management, staging, or prognosis and noncore elements which are clinically important, but not essential. Explanatory notes are provided for each element. Adoption of this updated data set will result in improvements in endometrial cancer patient care.

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.

Uncommon and Difficult High-Grade Endometrial Carcinomas

This article presents features of uncommon high-grade endometrial carcinomas that often pose a significant diagnostic challenge. An update on undifferentiated and dedifferentiated endometrial carcinoma is first provided, followed by discussions on more recently defined entities such as mesonephric-like carcinoma of the endometrium and gastric-type endometrial carcinomas. Finally, endometrial carcinoma with germ cell or trophoblastic-like components is discussed.

Gynaecological or gastrointestinal origin? Recognising Müllerian neoplasms with gastrointestinal phenotype and determining the primary site in selected entities

Recognising metastatic gastrointestinal and pancreatobiliary tumours to gynaecological sites may be challenging, as primary Müllerian tumours can demonstrate similar histological features. Endocervical adenocarcinomas can be of gastric and intestinal types, endometrial lesions may show gastrointestinal phenotype, and finally, mucinous tumours with secondary involvement of the ovaries may mimic primary neoplasms. The aim of this review is to address selected neoplastic entities of the gynaecological tract with gastric and intestinal differentiation and provide helpful clinical and pathological parameters for the diagnosis. A brief overview of metastatic tumours originating from the gastrointestinal and pancreaticobiliary tracts is also provided, including the most common pathological features.

Immunohistochemistry in gynecologic carcinomas: Practical update with diagnostic and clinical considerations based on the 2020 WHO classification of tumors

This review provides an update on immunohistochemistry applications-diagnostic, prognostic, and predictive-in the pathology evaluation of gynecologic carcinomas. The 5th edition of the WHO Classification of Female Genital Tumors introduced important changes in the diagnostic classification of lower genital tract, endometrial, and ovarian carcinomas, with major influence on the routine pathology practice. Lower genital tract carcinomas and their precursor lesions are now classified based on their human papillomavirus (HPV)-associated and HPV-independent pathogenesis, reflecting the clinically significant prognostic differences and impacting the therapeutic decision-making. Immunohistochemical markers have an increasing role in the pathology evaluation of endometrial carcinomas: in addition to their traditional use in the differential diagnosis and histologic subtyping, they have also been recently advocated for prognostic classification as surrogates for the TCGA (The Cancer Genome Atlas) molecular groups. New entities - mesonephric-like adenocarcinoma and gastric (gastrointestinal)-type mucinous adenocarcinoma of the endometrium - have also been added and often require immunostains for diagnostic confirmation. Ovarian carcinomas frequently show overlapping morphologic patterns and heterogeneous appearance within the same tumor, necessitating immunohistochemical work-up. Beyond diagnostic applications, there is increasing clinical demand for screening of inherited cancer syndromes, prediction of prognosis and guiding targeted therapy. Practical issues and pitfalls related to mismatch repair protein immunohistochemistry, HER2, and PD-L1 testing are also discussed.

Proceedings of the 2021 National Toxicology Program Satellite Symposium

The 2021 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri," was the 20th anniversary of the symposia and held virtually on June 25th, in advance of the Society of Toxicologic Pathology's 40th annual meeting. The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers' talks along with select images that were presented to the audience for voting and discussion. Various lesions and topics covered during the symposium included differentiation of canine oligodendroglioma, astrocytoma, and undefined glioma with presentation of the National Cancer Institute's updated diagnostic terminology for canine glioma; differentiation of polycystic kidney, dilated tubules and cystic tubules with a discussion of human polycystic kidney disease; a review of various rodent nervous system background lesions in control animals from NTP studies with a focus on incidence rates and potential rat strain differences; vehicle/excipient-related renal lesions in cynomolgus monkeys with a discussion on the various cyclodextrins and their bioavailability, toxicity, and tumorigenicity; examples of rodent endometrial tumors including intestinal differentiation in an endometrial adenocarcinoma that has not previously been reported in rats; a review of various rodent adrenal cortex lesions including those that represented diagnostic challenges with multiple processes such as vacuolation, degeneration, necrosis, hyperplasia, and hypertrophy; and finally, a discussion of diagnostic criteria for uterine adenomyosis, atypical hyperplasia, and adenocarcinoma in the rat.

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

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

[Current WHO classification of the female genitals : Many new things, but also some old]

The new WHO classification of tumors of the female genitalia entails some changes, especially those of prognostic and therapeutic relevance: there is a return to the term borderline tumor. Implants are again subdivided into noninvasive implants of the epithelial or desmoplastic type as before. Invasive extraovarian implants are classified as low-grade serous carcinoma (LGSC). Former seromucinous carcinomas are now classified as endometrioid carcinomas (seromucinous subtype). New entities of ovarian carcinomas are mesonephric-like adenocarcinoma, undifferentiated and dedifferentiated carcinoma, and mixed carcinoma. The classification of neuroendocrine neoplasms is analogous to that of pulmonary and gastrointestinal neuroendocrine neoplasms, regardless of their location. Endometrioid endometrial carcinoma can be classified into four molecular subtypes, which have significant prognostic significance. New subtypes include mucinous carcinoma of the intestinal type and mesonephric-like adenocarcinoma. Stromasarcomas of the endometrium are further subclassified based on specific molecular alterations. Adenocarcinomas (ACs) and squamous cell carcinomas (PECs) of the lower female genital tract are distinguished from HPV-associated and HPV-independent carcinomas. Block-like staining for p16 is the accepted surrogate immunohistochemical marker. Grading has not been reported for PEC. For HPV-associated AC of the cervix uteri, prognostic assessment is based on the pattern of invasion (so-called Silva pattern). Serous carcinomas in the cervix uteri are endometrial carcinomas with cervical infiltration.

Tumor Typing of Endocervical Adenocarcinoma: Contemporary Review and Recommendations From the International Society of Gynecological Pathologists

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.

Cervical carcinomas with serous-like papillary and micropapillary components: illustrating the heterogeneity of primary cervical carcinomas

Recent changes in the classification of cervical adenocarcinomas have re-categorized serous carcinoma as potentially nonexistent. However, clinical and pathological profiles of cervical adenocarcinomas with serous-like morphological features have not been systematically evaluated using the latest taxonomy and biomarkers. We studied 14 cases of primary cervical carcinomas with serous-like morphologies (papillary and micropapillary patterns). None of these cases exhibited evidence of serous carcinoma involving the upper tracts. Patient ages ranged between 34 and 86 years, most presented with abnormal uterine bleeding. Histologically, ten cases were classified as human papillomavirus (HPV)-associated carcinomas (eight usual-type endocervical adenocarcinomas and two adenosquamous carcinomas), of which six exhibited a papillary pattern and four had a micropapillary pattern. The four remaining cases were HPV-independent gastric-type adenocarcinomas, which displayed a papillary pattern in one case and a micropapillary pattern in three others. All ten HPV-associated carcinomas displayed block positive p16 and wild-type p53 by immunohistochemistry, with nine of them confirmed by HPV testing. Two of the four gastric-type adenocarcinomas had mutation-type p53, one of which also being p16 block positive. HER2 overexpression was demonstrated in 3/14 (21.4%) cases (2 HPV-associated and 1 HPV-independent). PD-L1 expression was identified in 4/10 (40%) cases, all HPV-associated. Targeted next-generation sequencing was performed in two cases with a micropapillary pattern, revealing a missense variant in ATM in an HPV-associated tumor and missense variants in TP53 and SMARCB1 in an HPV-independent tumor. The results demonstrated that primary endocervical adenocarcinomas can mimic the appearance of serous carcinoma, while not representing serous carcinoma. Serous-like papillary and micropapillary patterns may be present in both HPV-associated and HPV-independent cervical carcinomas, but none of the cases studied were unequivocally serous upon detailed analysis. Our findings support the exclusion of "cervical serous carcinoma" from existing classifications of cervical adenocarcinoma.

Endometrial Carcinomas with Intestinal-Type Metaplasia/Differentiation: Does Mismatch Repair System Defects Matter? Case Report and Systematic Review of the Literature

BACKGROUND

Intestinal metaplasia/differentiation in primary endometrial carcinomas is an uncommon phenomenon, with only few cases described.

MATERIAL AND METHODS

We performed a systematic review of endometrial carcinomas with intestinal metaplasia/differentiation interrogating the electronic databases Pubmed, Web of Science, and Scopus, and we reported an additional case arising in a 49-year-old woman.

RESULTS

We identified only eight patients diagnosed with endometrial carcinomas exhibiting intestinal metaplasia/differentiation, and additionally our case. Endometrial carcinomas with intestinal-type features can present in pure or mixed forms in association with usual-type endometrioid carcinomas; in mixed forms, the two neoplastic components may derive from a common neoplastic progenitor, as evidenced by the concomitant loss of MSH2 and MSH6 protein expression in our case. Disease recurrences occur in a significant fraction of the cases, including patients diagnosed in low-stage disease.

CONCLUSIONS

Endometrial carcinomas with intestinal metaplasia/differentiation are rare and they may represent a more aggressive tumor variant, thus requiring a proper treatment despite the low-tumor stage. The ProMise classification should be performed also in these unusual tumors, since they can be associated with mismatch repair system defects.