Patterns of keratin 19 expression in normal, metaplastic, condylomatous, atrophic, dysplastic, and malignant cervical squamous epithelium.

Keratin 19 (K-19) expression has been strongly correlated with dysplasia in oral epithelium. Expression of K-19 was evaluated by immunoperoxidase staining in formalin-fixed normal ectocervical tissue, normal endocervical tissue, cervical dysplasia, squamous metaplasia, atrophic epithelium, cervical condylomas, and invasive carcinoma to determine if a correlation of K-19 expression with dysplasia was present in the cervical epithelium. Uniform expression of K-19 was seen in endocervical epithelium and in the basal layer of normal ectocervical epithelium in all areas where these epithelia were present. Cervical dysplasia without associated condylomatous changes showed increased expression of K-19 in suprabasal epithelium, corresponding to the level of immature cells. Squamous metaplasia was characterized by scattered cells with increased staining (patch-quilt pattern). There was considerable overlap in the patterns of K-19 expression in dysplastic and metaplastic epithelium. Thus K-19 staining pattern could not be used as a distinctive marker for dysplasia in the cervical epithelium. Atrophic epithelium showed a characteristic uniform but low-level expression of K-19 in suprabasal areas. This pattern may be of diagnostic use in differentiating atrophic lesions from dysplasia. Condylomas showed focal loss of K-19 in the basal layer, suggesting induction of premature differentiation in the basal layer by human papillomavirus infection. Invasive carcinomas showed variable patterns. K-19 is a marker of immature cervical squamous epithelium, with generally distinctive but sometimes overlapping patterns of expression in various diagnostic categories.     

Basal-cell keratins in cervical reserve cells and a comparison to their expression in cervical intraepithelial neoplasia.

Expression of keratins 5, 14 and 17 in endocervical subcolumnar reserve cells was detected by means of immunohistochemical studies using polypeptide specific monoclonal antibodies. These particular keratins that were found among others in basal cells could also be detected to a variable extent in metaplastic and dysplastic cervical lesions. In some cases of immature squamous metaplasia all three keratin subtypes were expressed throughout the full thickness of the epithelium. In contrast, in mature squamous metaplasia a compartmentalization of these keratins was observed. Mature squamous metaplastic epithelium showed a keratin distribution pattern comparable to ectocervical squamous epithelium, with the exception of keratin 17, which was only sporadically found in the basal layer of ectocervical epithelium and was always present in the basal cells of mature squamous metaplastic epithelium. During progression of cervical intraepithelial neoplasia a clear increase in the expression of keratin 17 was observed. However, also keratins 5 and 14 were expressed. Our results demonstrate that a considerable number of premalignant lesions of the uterine cervix express the same keratins as found in the progenitor reserve cells. Lesions that lack expression of keratin 17 may form a distinct group, which are regressive in nature and do not progress into cervical cancer.     

Changing patterns of keratin expression during progression of cervical intraepithelial neoplasia.

The expression of keratins in normal cervical epithelia, metaplastic epithelium, and cervical intraepithelial neoplasia (CIN) grades I, II, and III is investigated with a panel of keratin polypeptide-specific monoclonal antibodies. This approach allowed the detection of individual keratins 4, 7, 8, 10, 13, 14, 18, and 19 at the single-cell level. By using an antibody recognizing keratins 5 and 8 (RCK 102) and two antibodies specific for keratin 8 (CAM 5.2 and M 20), it was also possible to derive information on the distribution of keratin 5. Our results show that during immature squamous metaplasia there is an acquisition of keratins typical of squamous epithelium, ie, keratins 4, 5, 13, and 14. This process continues during further differentiation to mature squamous metaplasia. In premalignant lesions the expression pattern of the progenitor reserve cells and immature squamous metaplastic epithelium is partly conserved. However, in most cases an induction in the expression of the keratins 4, 13, and 14 was observed. Furthermore, CIN III shows a more extensive expression of keratins typical of simple epithelia, ie, keratins 8 and 18, as compared to CIN I and CIN II.     

Metaplastic lesions of the extrahepatic bile ducts: a morphologic and immunohistochemical study.

Although metaplastic changes can occur in the extrahepatic bile ducts, a detailed morphologic study of these lesions has not been done. We examined the bile duct mucosa in 42 pancreaticoduodenectomy specimens, 32 with neoplastic lesions and ten with inflammatory lesions of the extrahepatic bile ducts, to assess the prevalence and type of metaplastic lesions. For comparison, the common bile ducts from 10 autopsy cases were reviewed. Twenty of the 42 total cases (48%), 13 of the 32 neoplastic cases (40%), and 7 of the 10 inflammatory cases (70%) had metaplastic changes. Pyloric gland metaplasia was the most common type (16/20 cases; 80%), whereas intestinal metaplasia was seen in 1/20 cases (5%). A combination of pyloric gland and intestinal metaplasia occurred in 2/20 cases (10%), and squamous metaplasia plus the above-mentioned two types of metaplasia was seen in 1/20 cases (5%). None of the normal common bile ducts obtained from ten autopsies had metaplastic changes. Endocrine cells were identified in nine (56%) of 17 metaplastic lesions. In contrast, endocrine cells within the intramural glands were seen in only 2 of the 10 normal common bile ducts. Although a significant proportion of carcinomas (6/13 cases) was in close proximity to areas of metaplasia, we were unable to find dysplastic foci within the metaplastic glands or the metaplastic surface epithelium. Reactive atypical cells involved the surface biliary epithelium and intramural glands and were associated with inflammation and metaplastic changes. The presence of goblet, mucinous, squamous, and reactive atypical cells in association with hyperplasia of intramural glands in frozen sections or small biopsy specimens may be mistaken for malignancy; hence, recognition of these lesions is of diagnostic importance.     

Variations of mitotic index in normal and dysplastic squamous epithelium of the uterine cervix as a function of endometrial maturation.

Cervical intraepithelial neoplasia is a premalignant (dysplastic) lesion that is characterized by abnormal cellular proliferation, maturation and nuclear atypia. The intraepithelial distribution, density, and nature (typical or atypical) of mitotic figures are routinely utilized diagnostic criteria to grade dysplasia and to distinguish high-grade dysplasia from potential histologic mimics such as transitional metaplasia, atrophy or immature squamous metaplasia. In this study, we evaluated the total mitotic indices of the cervical epithelia in hysterectomy specimens from patients with and without dysplastic lesions and investigated a possible relationship between mitotic index and hormonal status, using the endometrial maturation phase as a surrogate indicator of the latter. Two hundred seventy-four cervices from hysterectomy specimens (135 cases without dysplasia, 33, 35 and 71 cases with grades 1, 2 and 3 cervical intraepithelial neoplasia, respectively) were analyzed. A cervical mitotic index (total mitotic figures/10 high-power fields in the most proliferative area) was determined for each case. The endometrium in each case was classified into atrophic, early proliferative, late proliferative and secretory. For all three dysplasia grades, cases in the proliferative endometrium group always had a higher average mitotic index than those in the secretory and atrophic endometrium groups; this observation also held true for the benign cases. Furthermore, in all three dysplasia grades, the average mitotic index was always lowest in the atrophic endometrium group. Although the mitotic index showed expected patterns of increases with increasing dysplasia grades for most of the endometrial phases, this was not a universal finding. Notably, the average mitotic index for our cervical intraepithelial neoplasia 1 cases with late proliferative endometrium was higher than our cervical intraepithelial neoplasia 2 cases with secretory and atrophic endometrium. It is concluded that hormonal status, as reflected in endometrial maturation, can significantly affect the mitotic index of dysplastic squamous epithelium of the uterine cervix. Our findings confirm that the pathologic grading of dysplasia, especially in equivocal cases such as in metaplastic squamous epithelium, should not be solely dependent on the finding mitoses in the cervical squamous epithelium. The full composite of histopathologic features should form the basis for this determination.     

The histological and immunohistochemical evidence of squamous metaplasia from the myoepithelial cells in the breast

Squamous metaplasia in the breast is well documented. However, the putative cell of origin for the squamous epithelium is not clear. This paper describes a case of fibroadenoma of the breast with myoepithelial hyperplasia and squamous metaplasia. The histological finding of transition between myoepithelial cells and squamous cells and the immunohistochemical expressions of actin and S-100 in the metaplastic squamous cells support the myoepithelial origin of squamous epithelium in the breast.     

宫颈癌及其癌前病变的凝集素受体分布

112 cases of normal, dysplastic and neoplastic cervical epithelium were studied with a panel of twelve various lectins and ABC technique. The results showed that: (1) ConA and WGA receptors were relative to Squamous epithelial origin of the Cervix. (2) PNA, UEA-1, BSL and PHA receptors correlated with the tumorigenicity of cervical squamous epithelium. (3) WGA receptor correlated with the cell differentiation of squamous carcinomas. (4) DBA receptor was related with tumor invasion. (5) ConA and SJA receptors were related to the tumorigenicity of columnar epithelium of the endocervical glands. (6) Applications of neuraminidase caused compositional changes of glycoconjugates in the receptors of normal, dysplastic and malignant cervical epithelium and this may be of some value in clinical practice.     

'Senescence-associated' beta-galactosidase activity in the upper gastrointestinal tract

Beta-galactosidase activity at pH 6 is associated in vitro with senescence and cellular death, but in vivo data are sparse. This study undertook firstly to map 'senescence-associated' beta-galactosidase activity (SAbetaG) at pH 6 in normal epithelia and mucosae of the upper gastrointestinal tract. As escape from senescence confers a proliferative advantage, a reduction in SAbetaG activity might be predicted in neoplasia and their precursors in vivo. This prediction was tested in metaplastic, dysplastic, and neoplastic epithelium of the upper gastrointestinal tract. Histochemical staining for SAbetaG was performed at pH 6 on cryostat sections of 350 endoscopic biopsies from sites including oesophagus, stomach, and duodenum of 46 patients: 28 with Barrett's oesophagus (two with adenocarcinoma), 15 with gastric adenocarcinoma, and three with oesophageal squamous cancer. A staining score (range 0-6) was assigned to epithelial cells in all mucosae and scores were calculated for surface (luminal), intermediate, and deep (basal) layers. The strongest SAbetaG activity was in surface luminal cells of normal duodenal mucosa (mean score 3.6+/-0.5; n=19), 'specialized' Barrett's mucosa (mean 2.2+/-0.12; n=105), and intestinal metaplasia in the stomach (mean 2.4+/-0.40; n=16). Squamous epithelium was consistently negative for SAbetaG activity. Low- and high-grade Barrett's dysplasia showed no decrease in SAbetaG activity, but reduced activity was seen in gastric and oesophageal adenocarcinomas (mean 1.24+/-0.29; n=17; p=0.012). In six gastric adenocarcinomas, there was no detectable activity. Whether SAbetaG is truly a marker of cellular senescence in vivo remains to be determined. Activity is low in mucosal proliferation compartments and increases with cellular differentiation, especially in native or metaplastic intestinal mucosae. SAbetaG activity persists in dysplastic mucosae but may show some reduction or loss in adenocarcinomas (p=0.0012). Loss of SAbetaG activity is not, therefore, an early event in glandular dysplasia-neoplasia of the upper gastrointestinal tract.     

Controversies of the cardiac mucosa and Barrett's oesophagus

Confusion regarding the diagnosis of Barrett's oesophagus exists because of a false dogma that cardiac mucosa is normally present in the gastro-oesophageal junctional region. Recent data indicate that the only normal epithelia in the oesophagus and proximal stomach are squamous epithelium and gastric oxyntic mucosa. When this fact is recognized, it becomes easy to develop precise histological definitions for the normal state (presence of only squamous and oxyntic mucosa), metaplastic oesophageal columnar epithelium (cardiac mucosa with and without intestinal metaplasia, and oxynto-cardiac mucosa), the gastro-oesophageal junction (the proximal limit of gastric oxyntic mucosa), the oesophagus (that part of the foregut lined by squamous and metaplastic columnar epithelium), reflux disease (the presence of metaplastic columnar epithelium), and Barrett's oesophagus (cardiac mucosa with intestinal metaplasia). It is also possible to assess accurately the severity of reflux which is directly proportional to the amount of metaplastic columnar epithelium, and the risk of adenocarcinoma which is related to the amount of dysplasia in intestinal metaplastic epithelium present within the columnar lined segment of the oesophagus. Histopathological precision cannot be matched by any other modality and can convert the confusion that exists regarding diagnosis of Barrett's oesophagus to complete lucidity in a manner that is simple, accurate, and reproducible.     

Squamous metaplasia of the prostate. An immunohistochemical study

Immunoperoxidase strains for prostate-specific antigen (PSA), prostatic acid phosphatase (PAcP), epithelial membrane antigen (EMA), and cytokeratins (MAK 6 and CK-KES) were performed on 1 case of squamous cell carcinoma of the prostate and on 13 cases of squamous metaplasia of prostatic epithelium in an effort to demonstrate prostatic origin of the neoplastic and metaplastic cells and to differentiate them from primary or metastatic well-differentiated squamous cell carcinoma. The authors found no specific staining of the metaplastic or neoplastic cells for PSA and only focal single cell PAcP positivity in three cases of squamous metaplasia. All cases showed strong staining of surrounding normal glandular epithelium for both antigens. In all but one case, both the metaplastic and glandular epithelium had positive results for MAK 6 and CK-KES. EMA was expressed strongly in ten cases, was weak or variable in two, and had negative results in two cases of squamous metaplasia. In only four cases did the glandular epithelium have positive results for EMA. The remaining cases showed no staining. PSA and PAcP marking, therefore, may not be useful for separating atypical squamous metaplasia from well-differentiated squamous cell carcinoma or even primary prostatic from metastatic squamous cell carcinoma. These findings suggest that although prostatic glandular epithelial cells retain their ability to express some prostate-associated antigens, this ability is greatly reduced, lost, or not developed in cells that undergo metaplasia into squamous cells or that develop into squamous cell carcinoma.     

Squamous cell metaplasia of the bladder urothelium. A retrospective study of 36 patients.

In a retrospective study of 28 women and eight men with squamous cell metaplasia in different parts of the bladder, including the trigone, no histopathological differences were observed among the regions. All the five (female) patients with parakeratosis had a concomitant invasive bladder tumour. Thirty-eight% of all the patients had a simultaneous neoplastic tumour. The metaplastic lesions were investigated for keratin in 13 patients, and all were positive. In seven out of eight patients, the urothelium adjacent to the squamous cell metaplasia was also positive for keratin, indicating a direct transformation of the urothelium to squamous cell epithelium. The metaplastic cells were investigated for oestrogen receptors in five men and five women, and all were negative, suggesting no relationship between estrogens and squamous cell metaplasia of the bladder. Squamous cell metaplasia in the bladder is not considered a premalignant condition. However, metaplasia and neoplastic tumours are often associated with chronic tissue damage, and the presence of metaplasia may give a warning of conditions that can also cause cancer.     

Karyometry of pseudostratified, metaplastic and dysplastic nasal epithelium by morphometry and stereology. 2. Automated image analysis (IBAS) of the basal layer of nickel workers

A mathematical model for the stereological analysis of parallel-oriented, spheroidal nuclei has been applied to the basal layers of respiratory, metaplastic and dysplastic nasal epithelia. Nuclear profiles seen on tissue sections were measured with an automatic image analyser (IBAS). Nuclear profile area distributions were used to assess possible polyploidies. The result are compared to the histopathological grading, consisting of pseudostratified (respiratory), cuboidal, mixed cuboidal/squamous, squamous, and dysplastic epithelia. The estimated nuclear axis lengths, volumes, surface areas and volume/surface ratios are, in the great majority of cases, significantly smaller in pseudostratified or cuboidal epithelium than in squamous metaplasia and dysplasia. Correspondingly, the numerical density of the nuclei is lower in the latter cases, in which is also noted a smaller nuclear eccentricity. No significant difference is found between the nuclei of squamous and dysplastic epithelia. There is a clear correlation between the mean profile areas and the stereologically estimated volumes of the nuclei. When classifying the mean profile areas into four classes, a progressive shift from the smaller towards the larger size classes is observed when passing from pseudostratified to dysplastic epithelia, through the different metaplastic stages. The nuclear profile area plots often show several peaks, even in some pseudostratified and cuboidal epithelia, probably reflecting polyploidy. There is a marked tendency towards larger profile areas in squamous metaplasia and dysplasia. One histopathologically typical dysplasia showed only small-sized nuclei and another had a notable contribution of those in its profile area plot, in contrast with all the other dysplasias and squamous metaplasias, which displayed practically no small nuclei. The possible implications of the existence of "small-sized-nuclei-dysplasias" are discussed. The literature dealing with nuclear volumes or DNA quantities in putative preneoplastic situations in reviewed. Our method adds some valuable objective criteria to those used in classical histopathological grading. It should be possible to apply this method to other epithelial tissues.     

Skin calcium-binding protein in squamous metaplasia of human uterine cervix

The distribution of skin calcium-binding protein in squamous cell metaplasia of human endocervix, in normal human skin, and in ovarian cancer was determined by the immunofluorescence technique. A rabbit antiserum specific to rat SCaBP was characterized by Ouchterlony immunodiffusion and by immunoprecipitation of 125I-labeled SCaBP. The specificity of antibody labeling was demonstrated by using preimmune rabbit serum and SCaBP antiserum competitively absorbed with purified SCaBP. In normal human skin SCaBP was found exclusively in the basal layer cell cytoplasm. This protein was not detected in normal columnar epithelium of endocervix. Epithelial tissues in the zone of transition between the cylindrical epithelium of the endocervical mucosa and the stratified squamous epithelium of the exocervix were obtained from 14 patients with a wide variety of squamous cell metaplasia. In the early stage of metaplasia SCaBP was detected exclusively in the cytoplasm of reserve undifferentiated cells. In the terminal stage of metaplasia the SCaBP was present only in the basal cell layer. SCaBP was found in several layers of dysplastic tissue, and this distribution appeared to be related to the loss of normal maturation of the epithelium. SCaBP was also present in squamous cell carcinoma of endocervix especially in the least differentiated regions of the tumor. No SCaBP was detected in any ovarian cancer cells. These findings are potentially useful as a means of early detection of squamous metaplasia and of distinguishing premalignant anaplastic lesions from those that are benign and nonproliferative. In addition, the presence of SCaBP in tumors derived from metaplastic epithelia and its absence in the ovarian cancer indicate that immunohistochemical search for this protein might be of value in tumors in which an epidermoid origin is a possibility.     

Proliferation and number of Clara cell 10-kDa protein (CC10)-reactive epithelial cells and basal cells in normal, hyperplastic and metaplastic bronchial mucosa

Clara cell 10-kDa protein (CC10) is an inhibitor of phospholipase A2 and binds to phosphatidylinositol. It may therefore interfere with intracellular signal transduction. Bronchial CC10-reactive cells have been described by several authors. In contrast to the bronchiolar CC10-containing Clara cell, which is a progenitor cell of terminally differentiated airway epithelium, the role of bronchial CC10-reactive cells remains to be elucidated. We assessed the number of bronchial CC10-reactive cells in relation to cytokeratin (CK) expression and proliferative activity in normal, hyperplastic and squamous metaplastic epithelium. Sixty-five human bronchial mucosal specimens were investigated immunohistochemically for CK expression (CK7, CK13 and CK5/6), proliferative activity (MIB-1) and number of CC10-reactive epithelia. The proliferation fraction of CC10-reactive cells was assessed with double staining for MIB-1 and CC10. The proliferation index of the epithelium differed significantly between normal, hyperplastic and metaplastic epithelium. The number of CC10-reactive cells was inversely related to the epithelial proliferation. Bronchial CC10-reactive cells showed no proliferative activity as assessed using immunohistochemical double staining for CC10 and MIB-1. In contrast to normal and hyperplastic epithelium, squamous metaplasia disclosed CK5/6 in all epithelial layers, a loss of CK7 and a gain of CK13. We conclude that CC10-reactive cells have no progenitor role in the bronchial mucosa. However, because the proliferative activity is inversely related to the number of CC10-reactive cells, the CC10 protein may play a role in the regulation of epithelial repair. Squamous metaplasia most likely originates from basal cells.     

Epidermoid cyst of the spleen: a cytokeratin profile with comparison to other squamous epithelia

The stratified squamous epithelium of a splenic epidermoid cyst was studied with a battery of monoclonal antibodies to cytokeratin (CK) proteins. CKs 10 and 11 were found in the suprabasal layers of the stratified squamous epithelium, while staining for CK 13 was focal or diffuse throughout. CKs 18 and 19 decorated individual squamous cells or stained the entire thickness of the epithelium. These results were compared with those previously obtained by us in stratified squamous epithelia of ovarian mature cystic teratoma, fetal epidermis, adult epidermis and squamous metaplasia in a peritoneal cyst. From these comparisons it emerges that the epidermoid splenic cyst is either of teratomatous derivation or originates from inclusion of fetal squamous epithelium. Squamous metaplasia of mesothelium or inclusions of mature squamous epithelium appears to be an unlikely source of origin of these cysts.     

Ultrastructural characteristics of carcinogen-induced nondysplastic changes in tracheal epithelium

Nondysplastic hypotrophic and metaplastic epithelial alterations induced by dimethylbenz(a)anthracene in isogenic tracheal transplants were studied by light and electron microscopy 3--24 months after cessation of a 4-week carcinogen exposure. Hypotrophic epithelium observed at all time points was characterized by the presence of nonciliated cells that adopted either cuboidal or squamous shapes, forming simple or bistratified epithelia. Most of these cells, as well as some metaplastic cells, exhibited features of mucin-secreting cells. The metaplastic epithelia showed nonkeratinizing squamous metaplasia, closely related to transitional metaplasia, and keratinizing squamous metaplasia, which presented either an atrophic or an acanthotic epithelium. Although many of these epithelia showed morphologic features of normal stratified epithelia, several nonkeratinizing squamous metaplasias and acanthotic keratinizing squamous metaplasias exhibited some irregularities, probably representing very early atypical ultrastructural features (ie, perinuclear concentration of tonofilament bundles, the presence of dark and clear basal epithelial cells, interruptions and alterations of the basal lamina). These features were not observed in a group of early squamous metaplasias studied for comparative purposes 2 weeks after cessation of dimethylbenz(a)anthracene exposure, which were characterized by a combination of degenerative phenomena and increased cell proliferation.     

Negative loop electrosurgical excision procedure (LEEP) following cervical biopsy diagnosis of high grade squamous intraepithelial lesion

Context: Loop Electrosurgical Excision Procedure (LEEP) is commonly performed after cervical biopsy diagnosis of high grade squamous intraepithelial lesion (HSIL/CIN2 or CIN 3). Histological and immunohistochemical assessments are made to differentiate reactive and metaplastic changes from dysplastic changes. A Human Papillomavirus (HPV) test is used for prognostic assessment after conization. Objective: We retrospectively reviewed cases where the cervical biopsy showed HSIL but the LEEP specimen was negative for high grade dysplasia. Our aim was to determine the cause of miscorrelation. Data: IRB approval was obtained and a search was made of all LEEP specimens received during 2018. We reviewed 25 of 137 LEEP specimens that did not correlate with the diagnosis of HSIL rendered on the cervical biopsy. These were from women between 25 to 54 years. All cases had positive high-risk HPV with 80% being non16/18 subtype. On review, 8/25 had HSIL with the remainder of cases falling short of HSIL diagnosis. Follow up cytology with HPV test after the LEEP procedure was negative in all but one case of LSIL with persistent non-16/18 HPV. Conclusion: The study highlights the diagnostic difficulties of distinguishing HSIL from immature squamous metaplasia. The practical implication is that in cases with non-16/18 high risk HPV which have thin epithelium and fall short of definite morphologic criteria of HSIL, presence of immature squamous metaplasia should be carefully evaluated. The specific role of CK7 and CK17 which highlight squamocolumnar junctional cells and metaplastic cells, respectively, needs to be explored in these cases.     

Expression of epithelial membrane and 3-fucosyl-N-acetyllactosamine antigens in cervix uteri with particular reference to adenocarcinoma in situ.

The staining patterns obtained with antiepithelial membrane antigen (anti-EMA) and the monoclonal antibody to 3-fucosyl-N-acetyllactosamine (AGF 4:48) in the uterine cervix in intraepithelial and invasive neoplasia were compared to determine a possible role in differential diagnosis of reactive and neoplastic conditions. Both early invasive and in situ adenocarcinoma stained equally intensely with both agents and both antibodies stained diffusely tubal metaplasia, endometrial lined glands, and even occasional areas of normal endocervical mucosa. It is concluded that these agents are unlikely to be of use in the routine histological differentiation of glandular and squamous cervical dysplasia or neoplasia, but immunostaining with anti-EMA may help differentiate between reactive and metaplastic changes in endocervical glands and adenocarcinoma in situ.     

Expression of cyclin D1 in normal, metaplastic, hyperplastic endometrium and endometrioid carcinoma suggests a role in endometrial carcinogenesis

CONTEXT: Endometrioid carcinoma is often preceded by characteristic histopathologic lesions known as endometrial hyperplasia. Estrogen appears to be involved in the development of endometrioid carcinoma. Other mechanisms of endometrial carcinogenesis include mutations in p53 and PTEN tumor suppressor genes and overexpression of cyclin D1. However, the pattern of cyclin D1 expression is not well defined in normal, hyperplastic, neoplastic, and metaplastic endometrium. DESIGN: Cyclin D1 immunohistochemical analysis was used to evaluate 108 fixed, paraffin-embedded endometrial biopsy specimens and uterine resections obtained from 108 patients. Specimens included proliferative and secretory endometria, simple and complex hyperplastic lesions, and endometrioid adenocarcinoma. Normal and metaplastic surface epithelia were also evaluated independently of glandular morphologic features. RESULTS: Cyclin D1 was significantly overexpressed in glands with complex hyperplasia and endometrioid adenocarcinoma compared with proliferative or secretory endometrium and simple hyperplasia. Significant overexpression was also noted in papillary, syncytial, and squamous metaplasias compared with normal surface epithelium or epithelium with tubal metaplasia. CONCLUSION: Overexpression of cyclin D1 increases from normal endometrium to hyperplasia and carcinoma, suggesting that it may play a role in endometrial carcinogenesis. Overexpression of cyclin D1 in endometrial glands was independent from overexpression of cyclin D1 in surface metaplastic epithelium.