P16 Immunostaining Patterns in Microglandular Hyperplasia of the Cervix and Their Significance:

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.

Immunohistochemistry in Gynecologic Pathology: An Example-Based Practical Update

CONTEXT

- Immunohistochemical stains are routinely applied in the pathology diagnostic workup of gynecologic lesions. The rapidly expanding repertoire of available markers helps in refining the diagnostic criteria for each disease entity; however, limitations and pitfalls exist.

OBJECTIVE

- To provide a practical, relevant update on the use of immunohistochemistry for commonly encountered differential diagnoses in gynecologic pathology.

DATA SOURCES

- Literature review and authors' diagnostic experience.

CONCLUSIONS

- Immunohistochemistry is a helpful adjunct tool in gynecologic pathology. Although the primary application is in the diagnostic workup, novel prognostic and predictive markers, and immunostains to screen for genetic cancer syndromes, have also been recently introduced in the field.

[Cervical cancer : Update on morphology]

The World Health Organization (WHO) classification from 2014 differentiates between different subtypes of mucinous adenocarcinoma of the uterine cervix. A gastric subtype was recently described that showed no association with high-risk human papillomavirus (HPV) infections, has a poor prognosis, is mainly diagnosed in women of Asian origin and can occur in patients with Peutz-Jeghers syndrome. Although no clear grading system has been recommended in the WHO classification, it is likely that grading of adenocarcinomas of the uterine cervix will partly be based on the different patterns of invasion. Deep stromal infiltration of macroinvasive carcinomas is defined as an infiltration of >66 % of the cervical stroma. In the near future a maximum tumor size of 2 cm could act as a discriminator for planning of less radical surgery. Parameters of the histopathological report that are relevant for the prognostic assessment as well as the choice of adjuvant treatment and function as quality indicators during certification are described. The histological type of an adenocarcinoma alone is of no predictive or prognostic relevance for patients undergoing primary surgical treatment, neoadjuvant chemotherapy, combined chemo-radiotherapy or treatment with angiogenesis inhibitors. Currently, molecular parameters and biomarkers are of no relevance.

The spectrum of cervical glandular neoplasia and issues in differential diagnosis

CONTEXT

Premalignant and malignant glandular lesions of the cervix are known to often cause diagnostic problems with a variety of benign (more common) as well as other malignant mimics, the latter setting often being represented by secondary involvement by endometrioid endometrial carcinoma especially in small samplings.

OBJECTIVE

To highlight key histologic features and immunohistochemical markers that may be helpful in the distinction of in situ endocervical carcinoma from benign glandular proliferations, and those that separate different subtypes of invasive endocervical carcinoma, as well as invasive carcinoma from other carcinomas secondarily involving the cervix and nonneoplastic proliferations of the cervix.

CONCLUSIONS

Clinical and morphologic features as well as immunohistochemistry results should be used in conjunction in the differential diagnosis of glandular proliferations of the cervix, as correct interpretation has major clinical consequences for the patient in most instances (especially benign versus malignant). Immunohistochemical markers should be used as part of a panel of antibodies, as exceptions may occur to the usual pattern of staining, and if used singly, they may mislead the pathologist to establish a wrong diagnosis.

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.