Endometrioid adenocarcinoma arising from adenomyosis: Report and immunohistochemical analysis of an unusual case

Whether surgical procedure can improve the prognosis of endometrial cancer arising in adenomyosis (EC-AIA)? A systematic review and meta-analysis

PURPOSE

Endometrial cancer arising in adenomyosis (EC-AIA) is frequently detected accidentally following a general hysterectomy for adenomyosis. Whether supplemental lymphadenectomy in patients with EC-AIA can improve the survival outcome remains inconclusive. Herein, the authors summarized the data of patients with EC-AIA and further explored the impact of lymphadenectomy on the prognosis of these patients.

METHODS

Five electronic databases, namely MEDLINE, Web of Science, PubMed, Embase, and the Cochrane Library were employed for searching articles from inception to May 2023.

RESULTS

In total, 38 eligible studies enrolling 56 patients were included. Of these, 44 patients had a traceable prognosis. Kaplan-Meier curves demonstrated that patients who had undergone lymphadenectomy had a better progression-free survival (PFS) compared with those who had not undergone lymphadenectomy ( P =0.016), but there was no difference in overall survival. Univariable ( P =0.025, HR=0.25, 95% CI=0.08-0.84) and multivariable ( P =0.042, HR=0.13, 95% CI=0.020-0.930) Cox regression analyses revealed that lymphadenectomy was an independent protective factor for PFS.

CONCLUSION

For patients diagnosed with EC-AIA following hysterectomy for benign disease, further supplementary lymphadenectomy is recommended to improve PFS.

Ciliated Cell Variant of Endometrial Carcinoma in an Adenomyoma in Uterus

Ciliated cell variant of endometrioid adenocarcinoma (CCVEA) is an extremely rare tumor that has been seldom reported in the literature as low-grade endometrioid carcinoma with a favorable prognosis. CCVEA is characterized by neoplastic glands composed predominantly of ciliated cells with relatively little nuclear atypia. Recognition of the ciliated component is the key to the diagnosis of CCVEA but it can lead to diagnostic confusion with tubal metaplasia especially on endometrial biopsies. Herein, we report the case of a 56-year-old woman who presented with post-menopausal vaginal bleeding. Endometrial biopsy revealed extensive atypical complex endometrial hyperplasia composed predominantly of ciliated cells. The patient subsequently had a hysterectomy and bilateral salpingo-oophorectomy that revealed a large adenomyoma, adherent to the right ovary. The adenomyoma was extensively involved by CCVEA with some extension to the endometrial cavity. To the best of our knowledge, this is the first report of CCVEA that appears to arise in an adenomyoma.

Endometrial cancer arising from adenomyosis: Case report and literature review of MRI findings

Endometrial cancer arising from adenomyosis (EC-AIA) is extremely rare, and the typical magnetic resonance imaging (MRI) findings of EC-AIA have not been established. We report a case of EC-AIA that was detected preoperatively on MRI and conduct a literature review of the MRI findings of EC-AIA.

Endometrioid Adenocarcinoma Arising in Adenomyoma in a Woman with a Genital Prolapse - Case Report

BACKGROUND:

Endometrial cancer is the third-ranked genital malignancy in women and includes 3% of cancer deaths. There is a 2.8% chance of a woman developing endometrial cancer during her lifetime. Low-grade endometrioid adenocarcinomas are often seen along with endometrial hyperplasia, but high-grade endometrioid adenocarcinomas have more solid sheets of less-differentiated tumour cells, which are no longer organised into glands, often associated with surrounded atrophic endometrium.

CASE REPORT:

We present an unusual case of endometrial adenocarcinoma arising in adenomyoma in 74-year old woman presented with genital prolapse, without other clinical symptoms. Ultrasound evaluation revealed endometrium with 4 mm-thickness and atrophic ovaries. The cervical smear was normal. The patient underwent a total vaginal hysterectomy. The histopathology of the anterior uterine wall revealed an intramural adenomyoma of 4 mm in which some endometrial glands with malignant transformation of well-differentiated endometrioid adenocarcinoma without infiltration in surrounding myometrium and lymphovascular invasion were present. The endometrium lining the uterine cavity was predominantly atrophic, and only one focus of simplex and complex hyperplasia was found, with cell-atypia. According to AJCC/FIGO 2010, the tumour was classified: pTNM = pT1B pNX pMX G1 R0 L0 V0 NG1, Stage I. On dismiss, the near-future oncological consultation was recommended.

CONCLUSION:

We would like to point out the rare occurrence of such type of malignancy and the importance of meticulous histopathology evaluation, even after reconstructive surgery for genital prolapse.

Women with adenomyosis are at higher risks of endometrial and thyroid cancers: A population-based historical cohort study

Objective

Both adenomyosis and endometriosis are characterized by the presence of ectopic endometrial glands and stroma and have been suggested to share some characteristics with malignant tumors. Although accumulating evidence indicates that endometriosis is associated with some cancer types, the cancer risks in patients with adenomyosis have been rarely examined. In this study, we investigated the relationship between adenomyosis and risks of common cancers.

Methods

This study included a cohort of 12,447 women with adenomyosis but not endometriosis, born in 1951–1984, and a cohort of 124,470 adenomyosis-free women matched by birth year. Their medical records (collected between 1996 and 2011) were obtained from the National Health Insurance Research Database of Taiwan. We first compared the distribution of cancer-free survival (CFS) between cohorts with and without adenomyosis. Subsequently, within the adenomyosis cohort, we examined whether time-to-onset of the identified cancer type was correlated with time-to-onset of adenomyosis. The Cox proportional hazards model was used to compare the distribution of CFS between the adenomyosis and adenomyosis-free cohorts and between the early- and late-diagnosed adenomyosis groups. For comparison, we further evaluated the cancer risks for a cohort of 10,962 women with endometriosis but not adenomyosis and a birth-year matched cohort of 109,620 endometriosis-free women.

Results

Compared with adenomyosis-free women, patients with adenomyosis had higher risks of endometrial and thyroid cancers, with estimated hazard ratios (HRs) (95% confidence interval) of 2.19 (1.51–3.16) and 1.70 (1.29–2.24), respectively. For both cancers, distributions of CFS were not significantly different between the early- and late-diagnosed adenomyosis groups. Furthermore, compared with endometriosis-free women, patients with endometriosis had higher risks of endometrial and ovarian cancers, with HRs of 1.89 (1.07–3.35) and 2.01 (1.27–3.16), respectively.

Conclusions

Women with adenomyosis are at higher risks of endometrial and thyroid cancers, while women with endometriosis are at higher risks of endometrial and ovarian cancers.

Malignant changes in adenomyosis in patients with endometrial adenocarcinoma: A case series

The aim of the study is to describe the clinical characteristics and prognosis of malignant transformation of adenomyosis in patients with endometrial cancer.In this retrospective descriptive study, the clinical data of patients with endometrial cancer (n = 127) who were admitted at our hospital between January 2006 and December 2013 were evaluated.Among the 127 patients with endometrial cancer, 24 patients had endometrial cancer concurrently with adenomyosis. Among these 24 patients, 3 were diagnosed with malignant transformation of adenomyosis. Postoperative pathological investigations in the cancer+adenomyosis group revealed endometrial adenocarcinoma of Grade I (n = 21) and II (n = 3). The patients with malignant transformation of adenomyosis were relatively younger than the other patients. In those 3 patients, both the estrogen and progesterone receptors were strongly expressed in eutopic endometrium and were weakly positive in ectopic endometrium.Although adenomyosis is usually benign, it might also be a precursor of malignant disease. As the incidence of adenomyosis malignant transformation is low, and its clinical manifestations are nonspecific, it may only be confirmed by postoperative pathological examination. Further investigations on larger sample size may provide additional data about prognosis of adenomyosis malignant transformation.

Endometrial cancer arising in adenomyosis versus endometrial cancer coexisting with adenomyosis: are these two different entities?

PURPOSE

While adenomyosis is one of the most common benign histologic findings in hysterectomy specimens of endometrial cancer, demographics of endometrial cancer arising in adenomyosis (EC-AIA) has not been well elucidated. The aim of this study is to evaluate histopathological findings and disease-free survival (DFS) of EC-AIA in comparison to endometrial cancer coexisting with adenomyosis (EC-A).

METHODS

EC-AIA cases were identified via a systematic literature search (n = 46). EC-A cases were identified from a historical cohort that underwent hysterectomy-based surgical staging in two institutions (n = 350). Statistical comparisons of the two groups were based on univariate and multivariate analyses.

RESULTS

The EC-AIA group was significantly older than the EC-A group (58.9 versus 53.8, p = 0.002). As to tumor characteristics, 63.6% of EC-AIA cases reported tumor within the myometrium without endometrial extension. The EC-AIA group was significantly associated with more non-endometrioid histology (23.9 versus 14.8%; p = 0.002) and deep myometrial tumor invasion (51.6 versus 19.4%; p < 0.001) than EC-A. Tumor grade, stage, and nodal metastasis risk were similar (all, p > 0.05). In a univariate analysis, the EC-AIA group had a significantly decreased DFS compared to EC-A (5-year rates, 72.2 versus 85.5%, p = 0.001). After controlling for age, histology, tumor grade, and stage, EC-AIA remained an independent prognostic factor associated with decreased DFS compared to EC-A (adjusted-hazard ratio 2.87, 95% confidence interval 1.44-5.70, p = 0.031).

CONCLUSION

Our study demonstrated that EC-AIA has distinct tumor characteristics and a poorer survival outcome compared to EC-A. This suggests a benefit of recognition of this unique entity as an aggressive variant of endometrial cancer.

Tumor Characteristics and Survival Outcome of Endometrial Cancer Arising in Adenomyosis: An Exploratory Analysis

BACKGROUND

Endometrial cancer arising in adenomyosis (EC-AIA) is a rare entity of endometrial cancer, and its clinical significance has not been well studied. This study aimed to examine the tumor characteristics and survival outcomes of EC-AIA.

METHODS

An exploratory analysis was performed to compare EC-AIA and historical control cases. For this study, EC-AIA cases were identified via a systematic literature search using PubMed/MEDLINE with entry keywords "endometrial cancer OR uterine cancer" AND "adenomyosis" (n = 46). The control group comprised consecutive non-EC-AIA cases from four institutions that had hysterectomy-based surgical staging (n = 1294). Patient demographics, pathology results, and survival outcomes were evaluated between the two groups.

RESULTS

The EC-AIA group was significantly older than the control group (58.9 vs. 55.3 years; P = 0.032). In terms of tumor characteristics, 56.5% of the EC-AIA cases showed tumor within the myometrium without endometrial extension, and the EC-AIA group was significantly more likely to have tumors with more than 50% myometrial invasion (51.6 vs. 26.6%; P = 0.002) and serous/clear cell histology (22.2 vs. 8.2%, P = 0.002) while less likely to express estrogen receptor (14.3 vs. 84.6%; P < 0.001). Grade and stage distributions were similar (P > 0.05). In the univariate analysis, the EC-AIA group had a significantly poorer disease-free survival than the control group (5-year rate: 71.4 vs. 80.6%; P = 0.014). In the multivariate analysis, with control for age, ethnicity, histology, grade, and stage, EA-CIC remained an independent prognostic factor for decreased disease-free survival (adjusted hazard ratio, 3.07; 95% confidence interval 1.55-6.08; P = 0.001).

CONCLUSIONS

The study suggested that endometrial cancer arising in adenomyosis may be an aggressive variant of endometrial cancer.

The Risks for Ovarian, Endometrial, Breast, Colorectal, and Other Cancers in Women With Newly Diagnosed Endometriosis or Adenomyosis: A Population-Based Study

OBJECTIVE

Recent studies report a link between endometriosis and ovarian cancer (OC). Using a population-based cohort study to confirm the association between endometriosis and cancer is desirable. We thus examined the magnitude of the risks of OC, endometrial cancer (EC), breast cancer, colorectal cancer (CRC), and other cancers in women with newly diagnosed endometriosis or adenomyosis (internal endometriosis).

METHODS/MATERIALS

Women older than 20 years with claims data between 2003 and 2005 were identified from the Longitudinal Health Insurance Dataset containing 1 million individuals randomly sampled from the National Health Insurance Research Database. Those with preexisting malignancies, hysterectomy, or oophorectomy were excluded. The endometriosis cohort (n = 2266, including 768 cases of pure adenomyosis) and comparison cohort (n = 9064), formed by 1:4 matching, were followed up until incidence cancer, dropout, or December 31, 2008. Outcome measures included cancer incidence and adjusted hazard ratio by Cox model adjusted for age group, comorbidities, and endometriosis medication use.

RESULTS

With 9842 person-years of follow-up in endometriosis cohort and 36,274 person-years of follow-up in comparison cohort, there were increased risks of all cancers (adjusted hazard ratio, 1.8; 95% confidence interval, 1.4-2.4), OC (4.56, 1.72-12.11), and EC (4.05, 1.20-13.66). The ovarian endometriosis group was associated with increased risk of subsequent OC (4.37, 1.07-17.83). The adenomyosis group was strongly associated with both OC (5.50, 1.95-15.50) and EC (5.13, 1.36-19.40). Increased risk of subsequent CRC was observed in women with adenomyosis with coexistent endometriosis at other sites (13.04, 2.21-77.04). However, no statistically significant increased risk of breast or other cancers was observed.

CONCLUSIONS

Having limitations such as lacking of parity information which may affect the magnitude of risk estimates, this study demonstrates that ovarian endometriosis has a 4-fold increased risk of OC. Adenomyosis may associate with a 4- to 5-fold increased risk of OC and EC, and unexpectedly, a 13-fold increased risk of CRC.

Significance of adenomyosis on tumor progression and survival outcome of endometrial cancer

BACKGROUND

To examine the effects of adenomyosis on tumor progression and survival outcome of endometrial cancer patients.

METHODS

This is a retrospective study examining stage I-IV endometrial cancer patients who underwent hysterectomy-based surgical staging (n = 571), and endometrial hyperplasia patients who underwent hysterectomy (n = 213). Clinical demographics, histopathological factors, and survival outcomes were analyzed based on the presence or absence of adenomyosis.

RESULTS

Among the endometrial cancer cohort, adenomyosis was observed in 47.5 % of cases and was significantly associated with lower grade (grade 1-2 tumors, 81.2 vs. 73.3 %; p = 0.028), earlier stage (stage I disease, 74.8 vs. 64.3 %; p = 0.023), and lower likelihood of deep myometrial invasion (19.2 vs. 28.2 %; p = 0.039) and cervical invasion (13.7 vs. 21.2 %; p = 0.024) than those without adenomyosis. In survival analysis, endometrial cancer coexisting with adenomyosis was associated with a significantly better disease-free survival (5-year rate, 89.2 vs. 78.2 %; p < 0.001) and overall survival (91.8 vs. 83.9 %; p = 0.004) after hysterectomy. In multivariate analysis, controlling for other significant variables in univariate analysis, presence of adenomyosis remained an independent prognostic factor associated with decreased risk of disease recurrence after surgery (hazard ratio [HR] 0.53; 95 % confidence interval [CI] 0.30-0.92; p = 0.023). Endometrial hyperplasia had a significantly increased incidence of adenomyosis when compared with type I endometrial cancer (grade 1-2 endometrioid adenocarcinoma, n = 411) on multivariate analysis (62.9 vs. 48.9 %; HR 1.88; 95 % CI 1.32-2.69; p < 0.001).

CONCLUSIONS

Adenomyosis appears to be associated with less aggressive tumor behavior of endometrial cancer, suggesting that it may have inhibitory effects on the progression of this disease.

Small primary adenocarcinoma in adenomyosis with nodal metastasis: a case report

Background

Malignant transformation of adenomyosis is a very rare event. Only about 30 cases of this occurrence have been documented till now.

Case presentation

The patient was a 57-year-old woman with a slightly enlarged uterus, who underwent total hysterectomy and unilateral adnexectomy. On gross inspection, the uterine wall displayed a single nodule measuring 5 cm and several small gelatinous lesions. Microscopic examination revealed a common leiomyoma and multiple adenomyotic foci. A few of these glands were transformed into a moderately differentiated adenocarcinoma. The endometrium was completely examined and tumor free. The carcinoma was, therefore, considered to be an endometrioid adenocarcinoma arising from adenomyosis. Four months later, an ultrasound scan revealed enlarged pelvic lymph nodes: a cytological diagnosis of metastatic adenocarcinoma was made.

Immunohistochemical studies showed an enhanced positivity of the tumor site together with the neighbouring adenomyotic foci for estrogen receptors, aromatase, p53 and COX-2 expression when compared to the distant adenomyotic glands and the endometrium. We therefore postulate that the neoplastic transformation of adenomyosis implies an early carcinogenic event involving p53 and COX-2; further tumor growth is sustained by an autocrine-paracrine loop, based on a modulation of hormone receptors as well as aromatase and COX-2 local expression.

Conclusion

Adenocarcinoma in adenomyosis may be affected by local hormonal influence and, despite its small size, may metastasize.

Very Early Stage Adenocarcinoma Arising from Adenomyosis in the Uterus

OBJECTIVE

Malignant transformations of adenomyosis in premenopausal women with normal endometrium are extremely rare. We report a case of adenocarcinoma arising from an adenomyotic focus in the uterus, which was found unexpectedly in a woman undergoing myomectomy for adenomyosis.

CASE REPORT

A 47-year-old premenopausal woman presented with massive vaginal bleeding and anemia. She was admitted and underwent myomectomy under the initial diagnosis of uterine leiomyoma. Microscopic studies revealed endometrioid adenocarcinoma, which was a malignant transformation of a focus of adenomyosis in the surgical specimen. A total hysterectomy and bilateral salpingo-oophorectomy with pelvic and para-aortic lymphadenectomy was then performed. Pathologic studies showed no residual tumors in the entire resected specimen except for the previous lesion. The endometrium had normal thickness with mild proliferative activity throughout the cavity. There was no atrophic or hyperplastic change in the whole endometrium. The adenocarcinoma was present exclusively in the myometrium, and a transition between the carcinoma and the adenomyotic glands was observed.

CONCLUSION

This case report presents evidence that adenocarcinoma may a rise de novo from an adenomyotic lesion in the uterus.

[Adenomyosis: update on a frequent but difficult diagnosis]

Adenomyosis is a frequent entity, with difficult diagnosis, often obtained by pathological analysis performed after hysterectomy. This condition can cause abnormal uterine bleeding and dysmenorrhea, frequent reasons for consultation and hysterectomy. The development of ultrasonographic and magnetic resonance imaging techniques allow preoperative diagnosis. They also permit the use of hysteroscopic techniques for conservative uterine surgery, and have brought diagnosis and management of this disease to the front of the scene. This article reviews the pathological description of the disease, its epidemiology, clinical presentations, useful and necessary explorations, etiopathogeny and available therapies.

Invasive adenocarcinoma arising from uterine adenomyosis involving the rectosigmoid colon

We describe a rare case of invasive endometrioid adenocarcinoma arising from uterine adenomyosis involving the rectosigmoid colon. At laparotomy the uterus was densely adherent to the rectosigmoid colon. The final pathologic study of surgical specimens revealed intact endometrium and endometrioid adenocarcinoma scattered diffusely throughout the posterior myometrium with direct invasion into the rectosigmoid colon. There were numerous adenomyotic foci around the carcinoma. This case emphasizes the fact that biopsy findings from a uterus with adenocarcinoma arising from adenomyosis can be false negative. Physicians should keep in mind the possible existence of malignancies arising from adenomyosis when uterine malignancies are clinically suspected but histologic evaluation fails to confirm the diagnosis.

[Endometrioid adenocarcinoma arising from adenomyosis. A case report and literature review]

In spite of many references to carcinoma arising from endometriosis, there are few documented cases in the literature of endometrioid adenocarcinoma developed in association with adenomyosis. We report a case of endometrioid adenocarcinoma arising from adenomyosis. Carcinogenic and prognostic factors as well as the therapeutic consequences of this unusual situation are discussed. The use of hormonal replacement therapy by patients with a prior history of adenomyosis is also examined.

Endometrial Carcinoma in Adenomyosis:Assessment of Myometrial Invasion on T2-Weighted Spin-Echo and Gadolinium-Enhanced T1-Weighted Images

OBJECTIVE

The aim of our study was to compare T2-weighted and contrast-enhanced dynamic T1-weighted images with histologic findings in assessing the depth of myometrial invasion by endometrial carcinoma in adenomyosis.

MATERIALS AND METHODS

We retrospectively reviewed the MRIs of 11 patients who had a total of 12 lesions of endometrial carcinoma within adenomyosis. T2-weighted and contrast-enhanced dynamic T1-weighted images were compared with the histologic findings separately. We assessed the extent of myometrial invasion by endometrial carcinomas. The depth of myometrial invasion seen on MRI was classified as stage S (superficial invasion), stage D (deep invasion), or undetectable. The staging accuracies of each sequence were assessed. The tumor-myometrium contrast-to-noise ratios were calculated for each sequence.

RESULTS

The histologic specimens revealed that myometrial invasion was deep in seven of 12 lesions and superficial in five. On T2-weighted images the depth of invasion was underestimated in two lesions and impossible to determine in five lesions. On dynamic T1-weighted images the depth of invasion was overestimated in one lesion and underestimated in one lesion. The staging accuracy on dynamic T1-weighted images (83%) was significantly higher than that on T2-weighted images (42%). The contrast-to-noise ratio was significantly higher on dynamic T1-weighted studies during the early phase (mean +/- SD, 2.68 +/- 0.94) than it was on T2-weighted studies (1.74 +/- 1.05) and during the delayed phase (2.01 +/- 0.86).

CONCLUSION

When adenomyosis coexists with endometrial cancer at the same site on T2-weighted images, contrast-enhanced dynamic T1-weighted imaging improves the accuracy of staging.

The role of CD10 staining in distinguishing invasive endometrial adenocarcinoma from adenocarcinoma involving adenomyosis

Adenomyosis may be involved by endometrial adenocarcinoma, but in contrast to true myometrial invasion, the depth of an adenomyotic focus involved by carcinoma does not alter pathologic tumor staging. Therefore, distinction from carcinoma invading myometrium is clinically relevant. We hypothesized that CD10, a marker of non-neoplastic and neoplastic endometrial stroma, would highlight the stromal component of adenomyotic foci and be useful in this distinction. Thirty-nine cases of endometrial adenocarcinoma were analyzed and divided into three groups: I, invasive endometrial adenocarcinoma (n = 14); II, endometrial adenocarcinoma involving adenomyosis but without myometrial invasion (n = 18); and III, adenomyosis involved by endometrial adenocarcinoma with concomitant invasive component (n = 7). All cases of adenomyosis involved by endometrial adenocarcinoma demonstrated CD10 expression in the stromal cells of adenomyotic foci. Eleven of 21 cases (52%) of invasive adenocarcinoma also showed CD10 expression, at least focally, in cells immediately surrounding the infiltrating glands. Of these, two cases (from Group III) also had associated adenomyotic involvement by carcinoma. The remaining cases of invasive carcinoma were negative for CD10. Therefore, presence of CD10 staining immediately surrounding neoplastic glands does not equate with involvement of adenomyosis by endometrial adenocarcinoma. In contrast, absence of CD10 expression excludes involvement of adenomyosis by adenocarcinoma.

Adenocarcinomas arising from uterine adenomyosis: a report of four cases

Adenocarcinomas arising from adenomyosis uteri are rare. This study reports four such cases and characterizes them clinically and microscopically. In all four patients, the endometrial cytology was negative, and MR imaging and ultrasound sonography did not detect the tumors preoperatively. The histological subtypes of the four tumors were endometrioid (one grade 1, one grade 3), serous, and clear cell. In three cases, the adenocarcinomas were present exclusively in the myometrium, and a transition between the carcinomas and the adenomyotic glands was observed in all cases. The eutopic endometrium was normal except in one case in which there was a small focus of invasive carcinoma. In two of four cases, pelvic or paraaortic lymph node metastases were present. In the carcinomas, ER immunoreactivity was not found in any tumor and PR positivity was found in only one tumor. In contrast, p53 immunopositivity was found in three of four carcinomas. Adenocarcinomas arising from adenomyosis are difficult to diagnose preoperatively, and their aggressive behavior in some cases seems to be related to the histological subtype.

Endometrioid carcinoma of the uterine corpus: a review of its pathology with emphasis on recent advances and problematic aspects

This review considers the pathologic features of endometrioid carcinoma of the uterine corpus, which accounts for approximately 80% of endometrial adenocarcinomas, with an emphasis on its histologic features, recent advances, and problematic aspects. In addition to typical endometrioid carcinoma, the variants of endometrioid carcinoma covered include secretory carcinoma, villoglandular endometrioid carcinoma, endometrioid carcinoma with small nonvillous papillae, endometrioid carcinomas with microglandular and sertoliform patterns, and endometrioid carcinomas with metaplastic changes. These changes include a variety of different appearances of squamous epithelia (ranging from mature and keratinizing to immature with only subtle evidence of a squamous nature), clear cells, surface changes resembling syncytial metaplasia or microglandular hyperplasia, ciliated cells, oxyphilic cells, and spindled epithelial cells (sarcomatoid carcinoma). The last is one of several variants that may cause a biphasic appearance, all of which should be distinguished from the malignant müllerian mixed tumor. Rare findings in endometrioid carcinomas include hyalinization, psammoma bodies, and foci of stromal metaplasia such as osteoid. Unusual growth patterns of endometrioid carcinomas include involvement of adenomyosis, the "diffusely" infiltrating pattern of myoinvasion, and a previously unemphasized pattern of myoinvasion with "pinched off" glands that may be cystic or have a pseudovascular appearance, often with a myxoid stromal reaction. Other aspects of endometrioid carcinoma discussed are its immunoprofile, grading, cervical involvement (including a hitherto undescribed "burrowing" pattern of extension within the cervix that can result in underdiagnosis of stage IIB disease), carcinoma arising in the lower uterine segment, carcinoma arising in polyps and adenomyomas, carcinoma in young women, tamoxifen-related carcinoma, associated ovarian endometrioid carcinoma, and peritoneal keratin granulomas. Finally, the differential diagnosis of endometrioid carcinoma is briefly considered with a section on benign mimics, including curettage-related changes, menstrual changes, adenomyosis-related problems, metaplastic changes, atypical polypoid adenomyoma, radiation atypia, and papillary proliferations, and a section on metastatic colonic carcinoma.