Endometrial intraepithelial neoplasia
Encyclopedia
Endometrial Intraepithelial Neoplasia, (EIN) is a premalignant lesion of the uterine lining that predisposes to endometrioid endometrial adenocarcinoma. It is composed of a collection of abnormal endometrial cells, arising from the glands that line the uterus
, which have a tendency, over time to progress to the most common form of uterine cancer
— endometrial adenocarcinoma
, endometrioid type.
" The EIN diagnostic schema is intended to replace the previous "endometrial hyperplasia
" classification as defined by the World Health Organization
in 1994, which have been separated into benign
(benign endometrial hyperplasia) and premalignant (EIN) classes in accordance with their behavior and clinical management.
EIN should not be confused with an unrelated entity, serous intraepithelial carcinoma ("serous EIC"), which is an early stage of a different tumor
type known as papillary serous adenocarcinoma that also occurs in the same location within the uterus.
Risk factors for development of EIN and the endometrioid type of endometrial carcinoma include exposure to estrogens without opposing progestins, obesity, diabetes, and rare hereditary conditions such as hereditary nonpolyposis colorectal cancer
. Protective factors include use of combined oral contraceptive pills (low dose estrogen and progestin), and prior use of a contraceptive intrauterine device
.
Precancer Features of EIN (Table I). The cells of an EIN lesion are genetically different than normal and malignant tissues, and have a distinctive appearance under the light microscope. EIN cells are already neoplastic, demonstrating a monoclonal growth pattern and clonally distributed mutations. Progression of EIN to carcinoma, effectively a conversion from a benign neoplasm to a malignant neoplasm, is accomplished through acquisition of additional mutations and accompanied by a change in behavior characterized by the ability to invade local tissues and metastasize to regional and distant sites.
Table I: Precancer Characteristics of EIN
EIN Biomarkers. (Figure 1). There are no single biomarkers which are completely informative in recognition of EIN. The tumour suppressor gene PTEN is frequently inactivated in EIN, being abnormally turned off in approximately 2/3 of all EIN lesions. This can be seen with special tissue stains applied to histological sections known as PTEN immunohistochemistry
, in which the brown PTEN protein is seen to be absent in the crowded tubular glands that make up an EIN lesion.
, physicians who diagnose human disease by examination of histologic preparations of excised tissues. Critical distinctions in EIN diagnosis are separation from benign conditions such as benign endometrial hyperplasia (a field effect in endometrial tissue caused by excessive stimulation by the hormone estrogen
), and cancer.
The spectrum of disease which must be distinguished from EIN (Table II) includes benign endometrial hyperplasia and carcinoma:
Table II: Disease classes that need to be distinguished from EIN.
EIN may be diagnosed by a trained pathologist by examination of tissue sections of the endometrium. All of the following diagnostic criteria must be met in a single area of one tissue fragment to make the diagnosis (Table III).
Table III: EIN diagnosis.
Pathology
PTEN Gene
Other
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, which have a tendency, over time to progress to the most common form of uterine cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
— endometrial adenocarcinoma
Adenocarcinoma
Adenocarcinoma is a cancer of an epithelium that originates in glandular tissue. Epithelial tissue includes, but is not limited to, the surface layer of skin, glands and a variety of other tissue that lines the cavities and organs of the body. Epithelium can be derived embryologically from...
, endometrioid type.
History
EIN lesions have been discovered by a combination of molecular, histologic, and clinical outcome studies beginning in the 1990s which provide a multifaceted characterization of this disease. They are a subset of a larger mixed group of lesions previously called "endometrial hyperplasiaHyperplasia
Hyperplasia means increase in number of cells/proliferation of cells. It may result in the gross enlargement of an organ and the term is sometimes mixed with benign neoplasia/ benign tumor....
" The EIN diagnostic schema is intended to replace the previous "endometrial hyperplasia
Endometrial hyperplasia
Endometrial hyperplasia is a condition of excessive proliferation of the cells of the endometrium, or inner lining of the uterus.Most cases of endometrial hyperplasia result from high levels of estrogens, combined with insufficient levels of the progesterone-like hormones which ordinarily...
" classification as defined by the World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
in 1994, which have been separated into benign
Benign
A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...
(benign endometrial hyperplasia) and premalignant (EIN) classes in accordance with their behavior and clinical management.
EIN should not be confused with an unrelated entity, serous intraepithelial carcinoma ("serous EIC"), which is an early stage of a different tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
type known as papillary serous adenocarcinoma that also occurs in the same location within the uterus.
Clinical Aspects
The average age at time of EIN diagnosis is approximately 52 years, compared to approximately 61 years for carcinoma. The timeframe and likelihood of EIN progression to cancer, however, is not constant amongst all women. Some cases of EIN are first detected as residual premalignant disease in women who already have carcinoma, whereas other EIN lesions disappear entirely and never lead to cancer. For this reason, treatment benefits and risks must be individualized for each patient under the guidance of an experienced physician.Risk factors for development of EIN and the endometrioid type of endometrial carcinoma include exposure to estrogens without opposing progestins, obesity, diabetes, and rare hereditary conditions such as hereditary nonpolyposis colorectal cancer
Hereditary nonpolyposis colorectal cancer
Lynch syndrome is an autosomal dominant genetic condition which has a high risk of colon cancer as well as other cancers including endometrium, ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin...
. Protective factors include use of combined oral contraceptive pills (low dose estrogen and progestin), and prior use of a contraceptive intrauterine device
Intrauterine device
A copper IUD is a type of intrauterine device. Most IUDs have a plastic T- or U-shaped frame which is wrapped in copper wire, with the exception of Gynefix, which is a plastic string with several copper beads, affixed to the fundus of the uterus...
.
Biology
EIN lesions demonstrate all of the behaviors and characteristics of a premalignant, or precancerous, lesion.Precancer Features of EIN (Table I). The cells of an EIN lesion are genetically different than normal and malignant tissues, and have a distinctive appearance under the light microscope. EIN cells are already neoplastic, demonstrating a monoclonal growth pattern and clonally distributed mutations. Progression of EIN to carcinoma, effectively a conversion from a benign neoplasm to a malignant neoplasm, is accomplished through acquisition of additional mutations and accompanied by a change in behavior characterized by the ability to invade local tissues and metastasize to regional and distant sites.
Table I: Precancer Characteristics of EIN
| Precancer Characteristics | EIN Evidence |
|---|---|
| Precancers differ from normal tissue | |
| Precancers share some, but not all, features of cancer | |
| Precancers increase risk for carcinoma | |
| Precancers can be diagnosed | |
| Cancer must arise from cells within the precancer | |
EIN Biomarkers. (Figure 1). There are no single biomarkers which are completely informative in recognition of EIN. The tumour suppressor gene PTEN is frequently inactivated in EIN, being abnormally turned off in approximately 2/3 of all EIN lesions. This can be seen with special tissue stains applied to histological sections known as PTEN immunohistochemistry
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
, in which the brown PTEN protein is seen to be absent in the crowded tubular glands that make up an EIN lesion.
Diagnosis
Diagnosis of EIN lesions is of clinical importance because of the increased risk of coexisting (39% of women with EIN will be diagnosed with carcinoma within one year) or future (the long term endometrial cancer risk is 45 times greater for a woman with EIN compared to one with only a benign endometrial histology) endometrial cancer. Diagnostic terminology is that used by pathologistsPathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
, physicians who diagnose human disease by examination of histologic preparations of excised tissues. Critical distinctions in EIN diagnosis are separation from benign conditions such as benign endometrial hyperplasia (a field effect in endometrial tissue caused by excessive stimulation by the hormone estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
), and cancer.
The spectrum of disease which must be distinguished from EIN (Table II) includes benign endometrial hyperplasia and carcinoma:
Table II: Disease classes that need to be distinguished from EIN.
| Disease Class | Endometrial Topography | Functional Category | Treatment |
|---|---|---|---|
| Benign endometrial hyperplasia |
Diffuse | Hormone (estrogen) Effect |
Hormonal therapy |
| EIN, Endometrial Intraepithelial Neoplasia |
Focal progressing to diffuse (clonal) |
Precancer | Hormonal or surgical |
| Endometrial Adenocarcinoma |
Focal progressing to diffuse (clonal) |
Cancer | Surgical stage-based |
EIN may be diagnosed by a trained pathologist by examination of tissue sections of the endometrium. All of the following diagnostic criteria must be met in a single area of one tissue fragment to make the diagnosis (Table III).
Table III: EIN diagnosis.
| EIN Criterion | Comments | |
|---|---|---|
| 1 | Architecture | Gland area exceeds that of stroma, usually in a localized region. |
| 2 | Cytological Alterations |
Cytology differs between architecturally crowded focus and background. |
| 3 | Size greater than 1mm | Maximum linear dimension should exceed 1mm. Smaller lesions have unknown natural history. |
| 4 | Exclude mimics | Basalis, normal secretory, polyps, repair, lower uterine segment, cystic atrophy, tangential sections, menstrual collapse, disruption artifact, etc. |
| 5 | Exclude Cancer | Carcinoma should be diagnosed if: glands are mazelike and rambling, there are solid areas of epithelial growth, or there are significant bridges or cribriform areas. |
External links
Patient Resources- American Cancer Society
- Women's Cancer Network an educational and research organization
- Gynecologic Oncology Group an NIH-Funded research group that runs clinical trials
- OncoLink an excellent educational site from the U. of Pennsylvania
- Find a board certified specialist at the Society of Gynecologic Oncologists
Pathology
- US and Canadian Academy of Pathology
- www.endometrium.org a pathology site focusing on endometrial disease
PTEN Gene
- Cancer Genetics Web PTEN entry
- PTEN and the Endometrium at PubMed
- Entrez Gene PTEN entry
Other