Immunohistochemistry of Endometrial Carcinoma
W. Glenn McCluggage
Royal Group of Hospitals Trust
Belfast, Northern Ireland
Careful pathological sampling and morphological examination remains the mainstay in the
diagnosis of endometrial cancer. However, there are a few selected areas where immunohistochemistry
may be useful in the diagnosis of endometrial cancer1. This review will not detail those
immunohistochemical markers which are of value in a prognostic sense in endometrial cancer, since these
are few and in general confer no advantage over careful pathologic examination of routinely stained
sections. In addition, the immunohistochemical expression of markers such as PTEN and
ß-catenin which are implicated in the pathogenesis of endometrioid carcinomas will not be
detailed. It is stressed that most cases of endometrial cancer do not require immunohistochemistry, no
antibody is totally specific, the results of the immunohistochemistry should always be interpreted in the
context of the morphology and, in general, panels of antibodies should be used rather than relying on a
PANEL OF ANTIBODIES OF VALUE IN DISTINCTION BETWEEN TYPE 1 AND TYPE 2
A dual model of endometrial carcinogenesis is now well established. Type 1 carcinoma, the
prototype of which is endometrioid adenocarcinoma, is usually low grade, oestrogen-dependent and arises
in a background of endometrial hyperplasia in the perimenopausal or early postmenopausal age group. In
contrast, type 2 carcinoma, the prototype of which is uterine serous carcinoma (USC), commonly referred
to as papillary serous carcinoma, is a high grade neoplasm which is not oestrogen-dependent and which
usually arises in elderly postmenopausal women from an atrophic endometrium. Usually the morphological
distinction between an endometrioid adenocarcinoma and USC is straightforward but, on occasions, it may
be difficult for a number of reasons (it should be remembered that combined endometrioid and serous
neoplasms are not uncommon). Endometrioid adenocarcinoma may have a focal or diffuse papillary growth
pattern, including the villoglandular variant, and this may result in overdiagnosis of USC. Conversely a
glandular variant of USC exists with little or no papillary formation which may result in underdiagnosis
of USC. This is an argument for the nomenclature USC rather than uterine papillary serous carcinoma.
The nuclear features are different between endometrioid adenocarcinoma and USC but, in problematic cases,
immunostaining with anti-p53 (DO7), MIB1 and estrogen receptor (ER) may be of value2. Endometrioid
adenocarcinoma is usually positive with ER, exhibits a low to moderate proliferation index with MIB1 and
is largely negative with D07, although some endometrioid tumours, especially those of high grade, may be
positive with DO73 and negative with ER. Conversely, USC characteristically exhibits diffuse nuclear
positivity with DO7 and a high proliferation index with MIB1 but is negative with ER. The combination of
DO7, MIB1 and ER may be useful in diagnosing USC, especially the glandular variant. Conversely, diffuse
positivity with ER and negative staining with D07 in a papillary endometrial adenocarcinoma is against a
USC. As already stated, the glandular variant of USC may be overlooked and misdiagnosed as an
endometrioid adenocarcinoma. Generally, in endometrioid adenocarcinomas with good glandular formation,
the nuclear features are low grade and, although exceptions occur, the nuclear and architectural grades
usually are broadly similar. In a tumour with good glandular differentiation throughout, but with marked
cytologic atypia, a diagnosis of the glandular variant of USC should be considered. MIB1, DO7 and ER may
be useful in this scenario, as already described.
A recent study has shown that immunohistochemical staining with ß-catenin
and E cadherin may be of value in the distinction between grade 3 endometrioid adenocarcinoma and USC4.
Nuclear expression of ß-catenin is suggestive of an endometrioid carcinoma whereas
moderate or strong E cadherin staining is suggestive of USC.
FOCAL USC AND ENDOMETRIAL INTRAEPITHELIAL CARCINOMA (EIC) ARISING IN
ENDOMETRIAL POLYPS OR NON-POLYPOID ENDOMETRIUM
Previous reports have drawn attention to the fact that USC and its precursor lesion endometrial
intraepithelial carcinoma (EIC) may rarely involve and be largely confined to otherwise benign
endometrial polyps2,5-7. This is an argument for careful pathological sampling of endometrial polyps.
EIC may focally involve polypoid or non-polypoid endometrium and be easily overlooked. With EIC and USC
arising in otherwise benign endometrial polyps, there is usually an abrupt transition from glands lined
by atrophic or weakly proliferative endometrial epithelium to glands lined by cells with nuclear features
characteristic of EIC or USC. Pre-existing glands in EIC are lined by cells with markedly pleomorphic
nuclei, a high nuclear to cytoplasmic ratio, nuclear hyperchromatism and a high mitotic rate, often with
abnormal mitoses. D07 and MIB1 staining may be useful in highlighting the areas of EIC which could
otherwise be missed if they are focal2,8. The cells of EIC and USC are characteristically strongly
positive with D07, exhibit a high proliferation index with MIB1 and are ER-negative. This contrasts with
the surrounding endometrial epithelial cells which are ER-positive, D07-negative and exhibit a low
proliferation index with MIB1. An occasional problem in endometrial polyps is that degenerative changes
may occur resulting in focal, quite marked nuclear atypia. This is especially so when there is
associated metaplasia, eg oxyphil metaplasia. In such instances, staining with the aforementioned
antibodies may be useful in distinguishing degenerative nuclear atypia (D07-negative, low proliferation
index with MIB1, ER-positive) from EIC.
When small numbers of markedly abnormal cells are seen in endometrial biopsy or curettage
specimens admixed with atrophic endometrium, a diagnosis of EIC or USC should be suspected, especially in
an elderly postmenopausal woman. The aforementioned immunostains may facilitate a correct diagnosis.
The effects of radiation may also result in profound nuclear changes resembling EIC and the panel of
antibodies detailed may be useful in this instance.
DISTINCTION BETWEEN ENDOMETRIAL AND ENDOCERVICAL ADENOCARCINOMA
With small biopsy specimens the histological distinction between a primary endometrial and
endocervical adenocarcinoma may be difficult, although careful morphological examination usually allows a
confident distinction. In some cases, tumour is present in both endometrial and endocervical biopsies
and preoperative imaging procedures do not help in establishing the site of origin. The preoperative
distinction between an endometrial and an endocervical tumour is important since primary surgical
treatment may differ. Endometrial adenocarcinoma is usually treated by simple hysterectomy whereas
endocervical adenocarcinoma is generally managed by primary radiation therapy or by radical hysterectomy
and pelvic lymphadenectomy. Difficulties may also occur when in the resection specimen the tumour
involves the lower uterine segment and upper endocervix. Morphological clues as to the site of origin
include coexisting atypical endometrial hyperplasia, stromal foam cells or squamous morules, suggesting
an endometrial origin or foci of cervical adenocarcinoma in situ (AIS) suggesting an endocervical
origin. When there is doubt, immunohistochemical studies may assist. Recent reports have addressed the
value of vimentin, monoclonal CEA and ER staining9-11 and this combination of antibodies may be of value
in the distinction between a primary endometrial and endocervical adenocarcinoma. Endometrioid type
endometrial adenocarcinomas are characteristically diffusely positive with ER and vimentin but negative
with CEA (squamous morules often exhibit strong positivity with CEA). In contrast, primary cervical
adenocarcinomas of usual type are characteristically, although not always, CEA-positive and vimentin and
ER-negative (occasional cases exhibit focal weak nuclear positivity with ER). However, in some cases,
there is immunohistochemical overlap. The question also arises as to the immunophenotype of mucinous
adenocarcinoma of the endometrium and endometrioid adenocarcinoma of the cervix ie whether the
immunophenotype of these neoplasms is more dependent on the site of origin or the pattern of
differentiation. It should be stated that, in this author's opinion, endometrioid adenocarcinomas of the
cervix are rare, although in some institutions such a diagnosis is frequently made. A recent study
addressed the question of whether the immunophenotype of mucinous carcinoma of the endometrium and
endometrioid carcinoma of the cervix is more dependent on the site of origin or the differentiation of
the tumour11. It was concluded that ER staining is more dependent on the site of origin (positivity is
more common in endometrial than endocervical carcinoma), whereas vimentin positivity is more dependent on
the diffentiation of the tumour (being more common in endometrioid than mucinous neoplasms). However,
these authors concluded that if a tumour exhibited strong positive staining with vimentin and ER, then it
was almost certainly of endometrial origin.
Human papilloma virus (HPV) studies have also been found to be of value in the distinction
between an endometrial and an endocervical primary, especially if combined with some of the markers
listed above12. HPV is much more common in endocervical than endometrial adenocarcinomas, although it
should be acknowledged that several studies have identified HPV in a proportion of endometrial
adenocarcinomas13,14. A recent study found a combination of immunohistochemical staining with ER and
progesterone receptor (PR) and in situ hybridisation for HPV to be extremely useful in distinguishing
endometrial from endocervical adenocarcinomas12.
The cyclin-dependent kinase-4 inhibitor (CDK4-I), also known as p16, is the product of the
INK4-A gene and specifically binds to cyclin D-CDK4/6 complexes to control the cell cycle at the G1S
interphase. Increased expression of p16 has been shown in high grade cervical squamous intraepithelial
lesions and in low grade lesions associated with high risk HPV types15-17. Positive staining of cervical
AIS and adenocarcinoma has also been shown18,19. A recent study has shown that p16 staining may be of
value in distinguishing between an endometrial and an endocervical adenocarcinoma20, albeit with some
overlap. In general, endocervical adenocarcinomas exhibit diffuse positivity with p16 involving 100% of
cells. Endometrial adenocarcinomas are usually focally positive although small numbers of cases exhibit
diffuse positivity. The morphologically benign squamous elements of endometrial adenocarcinomas are
often diffusely positive with p16. Whether those endometrial adenocarcinomas which are diffusely
positive with p16 are associated with HPV should be addressed by further studies. It can be concluded
that p16 may be of some value in the distinction between an endometrial and an endocervical
adenocarcinoma, especially if used in conjunction with the other antibodies mentioned. Strong diffuse
positivity of 100% of cells with p16 favours an endocervical origin.
DISTINCTION BETWEEN USC AND OVARIAN SEROUS CARCINOMA
USC and ovarian serous carcinoma exhibit identical morphological features. In some cases, there
may be widespread involvement of the uterus, the ovaries and other organs and determining the site of
primary tumour may be difficult. A small USC without obvious myometrial involvement may occasionally
disseminate widely to involve the ovaries, omentum or peritoneum and with ovarian primaries there may be
extensive uterine involvement. In these scenarios it may be difficult or impossible to distinguish
between a USC and an ovarian serous carcinoma. This is important since adjuvant therapies for a uterine
and ovarian primary may differ. It is also possible that in some of these cases there are coexistent
independent primaries within the ovary and uterus. Molecular studies may assist and, in some cases of
USC with minimal or no myometrial infiltration but with ovarian involvement, such studies have confirmed
that the ovarian tumour represents metastatic disease rather than an independent primary21. A recent
study has examined the value of the WT1 (Wilm's tumour gene) antibody (which is positive in most ovarian
serous carcinomas22) in distinguishing between a USC and an ovarian serous carcinoma23. In that study
all USC were negative with WT1 whereas 97% of ovarian serous carcinomas were positive. It was concluded
that WT1 may be a useful immunohistochemical marker to distinguish between a USC and an ovarian serous
carcinoma. Clearly this requires confirmation by further studies.
CD10 IN ENDOMETRIAL ADENOCARCINOMAS
In recent years, the value of CD10 as a marker of endometrial stromal neoplasms has been
extensively studied24-26. CD10, although not specific for endometrial stromal neoplasms (some smooth
muscle tumours may be focally positive), may be useful as part of a panel, which should include
α-smooth muscle actin, desmin and h-caldesmon, in distinguishing between an endometrial stromal and
a smooth muscle neoplasm. Recently, CD10 positivity was shown in a presumed mesonephric adenocarcinoma
of the uterus and this antibody was proposed as a useful immunohistochemical marker of cervical
mesonephric lesions27. CD10 characteristically exhibits a luminal staining pattern in mesonephric
lesions. However, a recent study performed by us has shown that most endometrioid carcinomas of the
uterus are also positive with CD10 as are a third of usual endocervical adenocarcinomas (manuscript
submitted for publication). The conclusion is that CD10 is neither a specific nor a useful
immunohistochemical marker of mesonephric adenocarcinoma.
Since CD10 stains normal and neoplastic endometrial stroma, several studies have addressed the
value of CD10 in distinguishing between involvement of adenomyosis by endometrial adenocarcinoma and true
myoinvasion28-30. This distinction may be difficult morphologically and has important implications
regarding staging and treatment. In general these studies have shown than even around the myoinvasive
component of endometrial adenocarcinoma there is often a small rim of CD10 positive mesenchymal cells. I
have also consistently noted this phenomenon of staining of periglandular mesenchymal cells with CD10 in
the cervix (manuscript submitted for publication). It can be concluded that CD10 is of no value in
distinguishing true myoinvasive endometrial adenocarcinoma from involvement of adenomyosis.
MISCELLANEOUS USES OF IMMUNOHISTOCHEMISTRY IN ENDOMETRIAL
Some endometrial adenocarcinomas, either of endometrioid or mucinous type (more commonly
mucinous) may have a microglandular growth pattern31-33. There may be an associated neutrophilic
infiltrate and the morphological appearances can bear a close resemblance to cervical microglandular
hyperplasia (MGH). A microglandular growth pattern may also be seen, not uncommonly, on the surface of
many otherwise typical endometrial adenocarcinomas34 and these foci may be preferentially sampled on
endometrial biopsy. Although cervical MGH usually occurs in the premenopausal years, it may also occur
in the postmenopausal age group. In general, careful morphological examination allows a distinction
between microglandular adenocarcinoma and cervical MGH, but immunohistochemistry may be of value in
problematic cases. The proliferation marker MIB1 may be of value since, in most cases, cervical MGH has
a low proliferation index (less than 10%)18. The MIB1 index would be expected to be greater in
adenocarcinoma. However, since adenocarcinomas with a microglandular growth pattern are usually low
grade neoplasms, it is possible that these may also exhibit a low proliferation index. A recent study
investigated the value of a large panel of antibodies in distinguishing between microglandular
adenocarcinoma and cervical MGH35. Vimentin immunoreactivity was a strong pointer towards an
adenocarcinoma since most were positive whereas cervical MGH was invariably negative.
Occasionally the differential diagnosis in an endometrial biopsy or curettage specimen lies
between a metaplastic process and a carcinoma. Clear cell metaplasia may closely resemble endometrial
clear cell carcinoma. Although marked nuclear atypia and a high mitotic rate are indicative of a
malignant lesion, occasional clear cell carcinomas may be deceptively bland and may exhibit a low mitotic
count. Obviously the presence of a mass lesion on hysteroscopy is a pointer towards a carcinoma. ER
and D07 staining may be of value since most clear cell carcinomas are negative with ER and positive with
D07, although this is not invariably so36. Conversely, clear cell metaplasia would be expected to be
positive with ER and negative with D07.
- McCluggage WG. Recent advances in immunohistochemistry in gynaecological pathology. Histopathology
2002: 40: 309 – 326.
- Wheeler DT, Bell KA, Kurman RJ, Sherman ME. Minimal uterine serous carcinoma: diagnosis and
clinicopathologic correlation. Am J Surg Pathol 2000: 24: 797 – 806.
- Stewart RL, Royds JA, Burton JL et al. Direct sequencing of the p53 gene shows absence of mutations
in endometrioid endometrial adenocarcinoma expressing p53 protein. Histopathology 1998: 33: 440 – 445.
- Schlosshauer PW, Hedrick Ellenson L, Soslow RA.
ß-catenin and E-cadherin expression patterns in high-grade
endometrial carcinoma are associated with histological subtype. Mod Pathol 2002: 15: 1032 – 1037.
- Silva EG, Jenkins R. Serous carcinoma in endometrial polyps. Mod Pathol 1990: 3: 120 – 128.
- Carcangiu ML, Tom LK, Chambers JT. Stage IA uterine serous carcinoma: a study of 13 cases. Am J
Surg Pathol 1997: 21: 1507 – 1514.
- McCluggage WG, Sumathi VP, McManus DT. Uterine serous carcinoma and endometrial intraepithelial
carcinoma arising in endometrial polyps: report of five cases including two associated with tamoxifen
therapy. Human Pathol (in press).
- Ambros RA, Sherman ME, Zahn CM, Bitterman P, Kurman RJ. Endometrial intraepithelial carcinoma:
distinctive lesion specifically associated with tumors displaying serous differentiation. Human Pathol
1995: 26: 1260 – 1267.
- McClugage WG, Sumathi VP, McBride HA, Patterson A. A panel of immunohistochemical stains, including
carcinoembryonic antigen, vimentin and estrogen receptors aids the distinction between primary
endometrial and endocervical adenocarcinomas. Int J Gynecol Pathol 2002: 21: 11 – 15.
- Castrillon DH, Lee KR, Nucci MR. Distinction between endometrial and endocervical adenocarcinomas:
an immunohistochemical study. Int J Gynecol Pathol 2002: 21: 4 – 10.
- Kamoi S, Al Juboury MI, Akin M-R, Silverberg SG. Immunohistochemical staining in the distinction
between primary endometrial and endocervical adenocarcinomas: another viewpoint. Int J Gynecol Pathol
2002: 21: 217 – 223.
- Staebler A, Sherman ME, Zairo RJ, Ronnett BM. Hormone receptor immunohistochemistry and human
papillomavirus in situ hybridization are useful for distinguishing endocervical and endometrial
adenocarcinomas. Am J Surg Pathol 2002: 26: 998 – 1006.
- Czerwenka K, Lu YX, Heuss F, Manavi M, Kubista E. Human papillomavirus detection of endometrioid
carcinoma with squamous differentiation of the uterine corpus. Gynecol Oncol 1996: 61: 210 – 214.
- Fujita M, Shroyer KR, Markham NE et al. Association of human papillomavirus with malignant and
premalignant lesions of the uterine endometrium. Hum Pathol 1995: 26: 650 – 658.
- Keating JT, Cviko A, Reithdorf S et al. Ki-67, cyclin E and p16 (INK4) are complimentary surrogate
biomarkers for human papilloma virus-related cervical neoplasia. Am J Surg Pathol 2001: 25: 884 – 891.
- Klaes R, Friedrich T, Spitkovsky D et al. Overexpression of p16 (INK 4A) as a specific marker for
dysplastic and neoplastic epithelial cells of the cervix uteri. Int J Cancer 2001: 92: 276 – 284.
- Klaes R, Benner A, Friedrich T et al. p16INK4a immunohistochemistry improves interobserver agreement
in the diagnosis of cervical intraepithelial neoplasia. Am J Surg Pathol 2002: 26: 1389 – 1399.
- Cameron RI, Maxwell P, Jenkins D, McCluggage WG. Immunohistochemical staining with MIB1, bcl-2 and
p16 assists in the distinction of cervical glandular intraepithelial neoplasia from tubo-endometrial
metaplasia, endometriosis and microglandular hyperplasia. Histopathology 2002: 41: 313 – 321.
- Riethdorf L, Riethdorf S, Lee KR, Cviko A, Loning T, Crum CP. Human papillomaviruses, expression of
p16 INK4A, and early endocervical glandular neolasia. Hum Pathol 2002: 33: 899 – 904.
- McCluggage WG, Jenkins D. Immunohistochemical staining with p16 may assist in the distinction between
endometrial and endocervical adenocarcinoma. Int J Gynecol Pathol (in press)
- Baergen RN, Warren CP, Isacson C, Hedrich Ellenson L. Early uterine serous carcinoma: clonal origin
of extrauterine disease. Int J Gynecol Pathol 2001: 20: 214 – 219.
- Shimizu M, Toki T, Takagi Y, Konishi I, Fujii S. Immunohistochemical detection of the Wilm's tumor
gene (WT1) in epithelial ovarian tumors. Int J Gynecol Pathol 2000: 19: 158 – 163.
- Goldstein NS, Uzieblo A. WT1 immunoreactivity in uterine papillary serous carcinoma is different from
ovarian serous carcinomas. Am J Clin Pathol 2002: 117: 541 – 545.
- Chu PG, Arber PA, Weiss LM et al. Utility of CD10 in distinguishing between endometrial stromal
sarcoma and uterine smooth muscle tumors: an immunohistochemical comparison of 34 cases. Mod Pathol
2001: 14: 465 – 471.
- McCluggage WG, Sumathi VP, Maxwell P. CD10 is a sensitive and diagnostically useful
immunohistochemical marker of normal endometrial stroma and of endometrial stromal neoplasms.
Histopathology 2001: 39: 273 – 278.
- Oliva E, Young RH, Amin MB, Clements PB. An immunohistochemical analysis of endometrial stromal and
smooth muscle tumors of the uterus. A study of 54 cases emphasising the importance of using a panel
because of overlap in immunoreactivity for individual antibodies. Am J Surg Pathol 2002: 26: 403 –
- Ordi J, Nogales FF, Palacia A et al. Mesonephric adenocarcinoma of the uterine corpus: CD10
expression as evidence of mesonephric differentiation. Am J Surg Pathol 2001: 25: 1540 – 1545.
- Afify AM, Tan LC, Werness BA. The diagnostic utility of CD10 in evaluating endometrial lesions.
(Abstract). Mod Pathol 2002: 15: 189A.
- Nascimento AF, Hirsh MS, Cviko A et al. Distinction between invasive endometrial adenocarcinoma and
involvement of adenomyosis by adenocarcinoma. Can CD10 staining help? (Abstract). Modern Pathology
2002: 15: 204A
- Sroden M, Klein WM, Kurman RJ. Is CD10 a useful marker in distinguishing endometrial carcinoma
invading myometrium from carcinoma invading adenomyosis? (Abstract) Modern Pathol 2002: 15: 211A.
- Young RH, Scully RE. Uterine carcinomas simulating microglandular hyperplasia. A report of six
cases. Am J Surg Pathol 1992: 16: 1092 – 1097.
- Zaloudek C, Hayashi GM, Ryan IP, Bethan Powell C, Miller TM. Microglandular adenocarcinoma of the
endometrium. A form of mucinous adenocarcinoma that may be confused with microglandular hyperplasia of
the cervix. Int J Gynecol Pathol 1999: 16: 52 – 59.
- McCluggage WG, Perenyei M. Microglandular adenocarcinoma of the endometrium. Histopathology 2000:
37: 285 – 287.
- Jacques SM, Qureshi F, Lawrence WD. Surface epithelial changes in endometrial adenocarcinoma:
diagnostic pitfalls in curettage specimens. Int J Gynecol Pathol 1995: 14: 191 – 197.
- Qiu W, Mittal K. Comparison of morphologic and immunostaining patterns of cervical microglandular
hyperplasia with low nuclear grade mucinous adenocarcinoma of the endometrium (Abstract). Mod Pathol
2002: 15: 207A.
- Lax SF, Pizer ES, Ronnett BM, Kurman RJ. Clear cell carcinoma of the endometrium is characterised by
a distinctive profile of p53, Ki-67, estrogen and progesterone receptor expression. Hum Pathol 1998:
29: 551 – 558.