Aberrant Cdx2 expression in endometrial lesions with squamous differentiation: important role of Cdx2 in squamous morula formation

Morules but Not Squamous Differentiation are a Reliable Indicator of CTNNB1 (β-catenin) Mutations in Endometrial Carcinoma and Precancers

Although collectively regarded as "squamous differentiation (SD)" in endometrial endometrioid carcinoma (EEC) and atypical hyperplasia/endometrioid intraepithelial neoplasia (AH/EIN), morules (often referred to as "squamous morules") and true SD may represent two distinct phenomena. Here, we explored the distinction between morules versus SD and investigated the association of morules and SD with CTNNB1 mutations. A total of 270 cases of EEC and AH/EIN were studied, including EEC with (n=36) or without (n=36) morules and AH/EIN with (n=80) or without (n=118) morules. Cases were analyzed by immunohistochemistry and selected cases (n=20) by targeted next-generation sequencing panel. Near-perfect agreement was found between morules and glandular β-catenin nuclear staining in AH/EIN and EEC. A strong positive association was found between morules and glandular β-catenin nuclear staining (P<0.0001, Φ=0.59 in AH/EIN; P<0.0001, Φ=0.85 in EEC). There was no association between (1) morules and glandular PAX2 or PTEN aberrant expression or (2) SD and aberrant expression of β-catenin, PAX2 or PTEN (Φ=0.09, β-catenin; Φ=0.16, PAX2; Φ=0.13, PTEN). CTNNB1 mutations were identified in all 20 selected morule-containing cases (100%). Next-generation sequencing was performed on 2 (preprogestin and postprogestin treatment) biopsies from 1 patient, revealing identical mutational profile in morules and glands. In conclusion, (1) SD and morules are distinct biological phenomena; (2) the presence of morules, but not SD, is a reliable indicator of CTNNB1 mutations in EEC and AH/EIN. Our findings demonstrate that SD and morules are distinct biological phenomena. Since morules but not SD are associated with β-catenin mutations, the distinction is clinically relevant and should be included in diagnostic reports.

Diagnostic Pitfalls Related to Morular Metaplasia in Endometrioid Carcinoma: An Underestimated Issue

Here, we present a case that highlights the crucial pitfalls related to the presence of morular metaplasia (MM) in endometrioid carcinoma, which are insufficiently recognized in the routine pathology practice. A 45-year-old woman underwent hysterectomy with rectosigmoidectomy due to a 11-cm mass involving uterus, right ovary, and rectosigmoid colon. Histologically, the lesion appeared as a predominantly solid carcinoma with a minor glandular component. Results of the first immunohistochemical analysis suggested a colorectal origin (PAX8-, CK7-, WT1-, hormone receptors-, and CDX2+ in the absence of mucinous features). Subsequent immunohistochemistry (nuclear β-catenin+, CD10+, and low ki67 in the solid areas) supported a diagnosis of endometrioid carcinoma with diffuse MM. This case remarks that morphological and immunohistochemical features of MM may conceal the glandular architecture and the typical immunophenotype of endometrioid carcinomas. Acknowledging the diagnostic issues related to MM appears crucial to avoid misdiagnosis and inappropriate patient management.

Adenocarcinoma NOS arising from accessory lacrimal glands: A case report and a review of the literature

Primary malignant epithelial tumours arising from accessory lacrimal glands (ALGs) are extremely rare, with only few cases reported in literature. They generally appear as gradually increasing masses of the upper or the lower eyelid. Only one case of primary adenocarcinoma or adenocarcinoma not otherwise specified (ACNOS) from ALGs has been reported in literature. Herein, we describe a case of ACNOS arising from ALGs with an atypical clinical presentation and review prior cases of ALGs epithelial malignancies reported in the literature. A 78-year-old man referred to our Ocular Oncology Unit for adjuvant therapy after the excision of a conjunctival tumour of the left eye with a histological diagnosis of squamous cell carcinoma. He underwent topical chemotherapy with MMC and during follow up he presented a multinodular iris mass in his left eye. The MRI of the orbit showed an ocular mass infiltrating orbital soft tissues of the inferior palpebral region with an involvement of the corresponding zygomatic cutis. We performed orbital exenteration and histological studies revealed an epithelial neoplasm with a solido-glandular growth pattern with lumens containing an eosinophilic material positive for PAS and PAS-D. The immunohistochemical findings confirmed the diagnosis of adenocarcinoma NOS from ALGs. Although ALGs epithelial malignancies are extremely uncommon, they should be considered in the differential diagnosis of ocular tumours. A vigilant approach towards these entities is required, since they can be clinically insidious and locally aggressive.

Relationship between morular metaplasia and squamous differentiation in endometrial carcinoma

Morular metaplasia (MM) is a peculiar type of metaplastic change commonly observed in endometrial lesions, which is defined by the absence of overt squamous features and a characteristic immunophenotype. The nature of MM and its relationship with conventional squamous differentiation (SD) is still undefined. Here, we present a morphological and immunophenotypical study of cases with mixed MM/SD and conventional SD, providing new insights on this field. Twenty cases of endometrioid carcinoma (10 with mixed MM and SD and 10 with conventional SD) were assessed by immunohistochemistry for β-catenin, CD10, CDX2, ki67, p63, p40, estrogen receptor (ER), progesterone receptor (PR) and cytokeratins (CK) 5/6, 7, 8/18 and 19. In mixed MM/SD cases, SD was mostly located within the MM areas; several degrees of SD development were observed within MM, from cells with larger cytoplasm and prominent membrane, to overt SD with morular shape and ghost cell keratinization. In the MM→SD transition, there was progressive loss of nuclear β-catenin, CD10, CDX2 and CK8/18 expression, increase of CK5/6 and CK7 expression, and stable CK19 positivity. ER, PR and ki67/MIB1 expression was low-to-negative in both MM and SD. The squamous cell markers p63 and p40 were mostly expressed at the interfaces between MM and SD. Conventional SD cases showed direct transition from glandular epithelium to SD with a surface growth and no ghost cell keratinization; immunohistochemistry showed strong positivity for ER, PR and all CKs, basal positivity for p63, p40 and ki67/MIB1, negativity for nuclear β-catenin, CD10 and CDX2. In conclusion, MM appears as the precursor of a peculiar form of SD, which differs morphologically and immunophenotypically from conventional SD. Defining MM based on the absence of overt squamous might not be meaningful. Further studies are necessary to clarify the nature of MM.

Squamous differentiation portends poor prognosis in low and intermediate-risk endometrioid endometrial cancer

BACKGROUND

Endometrial cancer presents well-defined risk factors: myometrial invasion, histological subtype, tumor grade, lymphovascular space invasion (LVSI). Some low and intermediate-risk endometrioid endometrial cancer patients exhibited unexpected outcomes. This study aimed to investigate other clinical-pathological factors that might influence the recurrence rates of patients diagnosed with low and intermediate-risk endometrioid endometrial cancer.

METHODS

A case-control study from a cohort retrospective of 196 patients diagnosed with low and intermediate-risk endometrioid endometrial cancer at a single institution from 2009 to 2014 was conducted. Medical records were reviewed to compare clinical (race, smoking, menopause age, body mass index) and pathological (endometrioid vs endometrioid with squamous differentiation, tumor differentiation grade, tumor location, endocervical invasion, LVSI) features of patients with recurrence (case) and without recurrence (control) of disease. Three controls for each case were matched for age and staging.

RESULTS

Twenty-one patients with recurrence were found (10.7%), of which 14 were stage IA, and 7 were stage IB. In accordance, 63 patients without recurrence were selected as controls. There were no significant differences in any clinical characteristics between cases and controls. Among pathological variables, presence of squamous differentiation (28.6% vs. 4.8%, p = 0.007), tumor differentiation grade 2 or 3 (57.1% vs. 30.2%, p = 0.037) and presence of endocervical invasion (28.6% vs. 12.7%, p = 0.103) were associated with disease recurrence on a univariate analysis. On multivariable analysis, only squamous differentiation was a significant risk factor for recurrence (p = 0.031).

CONCLUSION

Our data suggest that squamous differentiation may be an adverse prognostic factor in patients with low and intermediate-risk endometrioid endometrial cancer, that showed a 5.6-fold increased risk for recurrence.

Benign and Premalignant Lesions of the Endometrium

In this review, we highlight the benign and premalignant lesions of the endometrium that the pathologist may encounter in daily practice. We begin by detailing our current understanding of excess estrogen in the progression of endometrial neoplasia. We outline the currently accepted terminology to be used when evaluating proliferative endometrial lesions, while highlighting their key features. Attention is then turned to the molecular underpinnings of neoplastic progression and how this can be exploited with immunohistochemical stains when appropriate. Finally, we discuss types of metaplasia and their associations, including so-called papillary proliferations of the endometrium.

Two Cases of Sinonasal Non-Intestinal-Type Adenocarcinoma with Squamoid Morules Expressing Nuclear β-Catenin and CDX2: A Curious Morphologic Finding Supported by Molecular Analysis

Sinonasal non-intestinal-type adenocarcinoma (non-ITAC) is a rare, morphologically diverse neoplasm of the head and neck. Squamoid morular metaplasia has recently been reported as an occasional finding in non-ITAC. Interestingly, these squamoid morules often show aberrant expression of CDX2 as well as nuclear expression of β-catenin, similar to other tumors that show this type of metaplasia, but the underlying mechanism responsible for this finding is not completely understood. We present two cases of low-grade non-ITAC with squamoid morules coexpressing CDX2 and nuclear β-catenin by immunohistochemistry, both of which were found to harbor a mutation in CTNNB1, the gene encoding β-catenin. This finding provides support that an alteration in the β-catenin pathway, including mutations in the β-catenin gene itself, is responsible for this recently described morphologic phenomenon in non-ITAC.

Histopathologic Features of Colorectal Adenoma and Adenocarcinoma Developing Within Inflammatory Polyps in Miniature Dachshunds

Biopsy samples of colorectal polyps were collected and examined from 67 Miniature Dachshund dogs (including 35 cases with an additional biopsy). Histopathologic diagnoses of the initial biopsy samples were "inflammatory polyp" in 52 cases (78%), "adenoma" in 10 cases (15%), and "adenocarcinoma" in 5 cases (8%). Eight of 10 cases (80%) diagnosed as adenoma also had inflammatory polyp lesions in the same specimen. A second biopsy was performed in 25 cases (48%) initially diagnosed with inflammatory polyp. Pathologic diagnoses for the second biopsy were inflammatory polyp in 11 cases (44%), adenoma in 9 cases (36%), and adenocarcinoma in 5 cases (20%). The number of beta-catenin-positive nuclei in epithelial cells was significantly higher in adenoma (46%) and adenocarcinoma (75%) as compared with inflammatory polyp (6%). Normal epithelial cells and hyperplastic goblet cells in inflammatory polyps showed homogeneous positive cytoplasmic immunoreactivity for adenomatous polyposis coli (APC) antigen. However, APC expression was decreased in areas of intense nuclear beta-catenin expression in adenoma and adenocarcinoma lesions. Foci of cytokeratin 5/6-positive squamous cell-like neoplastic cells showed intense beta-catenin nuclear expression that was similar to squamous morules described in human colorectal tumors. The results of the present study suggest that the inflammatory polyp in Miniature Dachshunds is a progressive disease that may develop into adenoma and/or adenocarcinoma. In addition, immunohistochemical findings suggest that aberrations of APC and beta-catenin expression may be involved in tumor development within the inflammatory polyp lesions.

Pyloric Gland Adenoma of Gallbladder: A Review of Diagnosis and Management

Neoplastic polypoid mucosal lesions of the gallbladder are increasingly being reported in cholecystectomy specimens. However, due to the absence of unified terminology and reporting criteria, the body of scientific evidence on their classification, prognosis, and management is scarce and sometimes controversial. While they have different histomorphologic features (gastric foveolar, gastric pyloric gland, biliary, and intestinal), a significant immunohistochemical overlap exists which highlights their mixed cell lineage with a dominant cell type in each, establishing the subcategory. Because of many shared attributes, intracholecystic papillary-tubular neoplasm (ICPN) has been introduced as an umbrella terminology. ICPNs of the pyloric subtype are lesions larger than 1 cm, as most of the smaller ones are clinically insignificant and represent polypoid hyperplasia rather than a true neoplasm. In this review, we will focus on the pyloric gland adenomas as the most frequent histologic subtype of ICPNs.

Diagnostic immunohistochemistry in gynaecological neoplasia: a brief survey of the most common scenarios

Immunohistochemistry is a valuable adjunct in routine gynaecological pathology. The molecular revolution has redesigned knowledge of gynaecological cancers and refined histological classification. The direct consequence has been the progressive introduction of new immunostainings for diagnostic and classification purposes. Hence, we review the routine diagnostic use of immunohistochemistry in the field of gynaecological neoplasia. We reviewed the immunomarkers useful in gynaecological pathology according to literature revision, our personal experience and research findings. We discuss the application of immunohistochemistry to reach the most accurate diagnosis in morphologically equivocal cases of gynaecological pathology and present the appropriate panel of immunomarkers in the most common scenarios of gynaecological pathology. This short review provides an updated overview of the essential immunohistochemical markers currently used in the diagnostics of gynaecological malignancies along with their molecular rationale.

CDX2 immunostaining in primary and metastatic germ cell tumours of the testis

Objective To evaluate the immunohistochemical staining pattern of caudal type homeobox 2 (CDX2) protein in germ cell tumours (GCTs) of the testis. Methods This study reassessed archival tissue samples collected from patients diagnosed with primary and metastatic testicular GCTs for CDX2 immunoreactivity using standard immunohistochemical techniques. Positive nuclear immunostaining was evaluated with regard to both the staining intensity and the extent of the staining. Results Tissue sections from primary and metastatic testicular GCTs ( n = 104), germ cell neoplasia in situ (GCNis) ( n = 5) and benign testicles ( n = 15) were analysed. The GCNis and benign testicular tissues showed no immunoreactivity for CDX2. Strong and diffuse staining of CDX2 was demonstrated only in the mature colonic epithelium of teratomas in both primary and metastatic GCTs. CDX2 positivity in other tumours (one pure yolk sac tumour, one yolk sac component of a mixed GCT and one pure seminoma) was infrequent, and was only weak and focal. Conclusions CDX2 immunostaining should be interpreted based on both the staining intensity and the extent of staining so as not to cause misdiagnosis. Teratomas with colonic-type epithelium should be considered in the differential diagnosis if a metastatic tumour with an unknown primary shows prominent CDX2 immunostaining.

Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site

CONTEXT

-Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes.

OBJECTIVES

-To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features.

DATA SOURCES

-Literature review, the authors' practice experience, and authors' research.

CONCLUSIONS

-With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls.

Squamous morula formation in colorectal adenoma: Immunohistochemical and molecular analyses

Little is known about the squamous morular component (SMC) in colorectal neoplasms because of its rarity. The aim of the present study is to elucidate the morphological, immunohistochemical and genetic characteristics of SMCs in colorectal adenomas. Five colorectal adenomas having SMCs were resected from five patients endoscopically. On immunohistochemical examination (four cases), all SMCs were positive for cytokeratin 5/6 in their cytoplasm and positive for β-catenin in their cytoplasm and nuclei. A nuclear positivity of p63 was detected in one SMC. All SMCs were negative for p53, chromogranin A, synaptophysin and NCAM. There was no Ki-67 expression in any of the SMCs. We detected none of mutations of β-catenin, KRAS and BRAF by microdissection and polymerase chain reaction-direct sequence in any of the four examined SMCs. SMCs are a rare but problematic finding in colorectal adenomas. Using immunohistochemistry for β-catenin, cytokeratin 5/6, Ki-67, p53, chromogranin A, synaptophysin and NCAM can facilitate the diagnosis of these peculiar cell nests.

A Subset of Sinonasal Non-Intestinal Type Adenocarcinomas are Truly Seromucinous Adenocarcinomas: A Morphologic and Immunophenotypic Assessment and Description of a Novel Pitfall

While sinonasal intestinal type adenocarcinoma (ITAC) is defined by an intestinal phenotype, non-intestinal type adenocarcinoma (non-ITAC) is traditionally viewed as a diagnosis of exclusion, despite previous implication of a seromucinous phenotype and similarity to sinonasal seromucinous hamartomas (SSH). We performed a comparison of clinicopathologic and immunophenotypic features of ITAC, non-ITAC and SSH using traditional discriminatory markers and new markers of seromucinous differentiation. Twenty-three non-ITAC, 17 ITAC, and 5 SSH were retrieved (1987-2014). As expected, ITAC occurred predominantly in the nasal cavity in elderly patients (mean age 65 years) with a striking male predilection (15:2). Regardless of grade/subtype, all ITAC were invariably CK20 and CDX2 positive, and many (11/15) showed some CK7 positivity. Non-ITAC occurred in younger individuals (mean age 51 years) with a slight female predilection (male to female ratio: 10:13) and showed diverse morphologic patterns and grades, some with morphologic similarity to SSH. SSH occurred in younger individuals (mean age 33 years). Non-ITAC and SSH were invariably CK7 positive and CK20 negative, however, 4/22 non-ITAC and 2/5 SSH showed squamoid morular metaplasia that aberrantly expressed CDX2 and co-expressed nuclear β-catenin. Markers of seromucinous differentiation (S100, DOG1, and SOX10) were essentially absent in ITAC, but present to varying degrees in the majority of non-ITAC and all SSH. Thus, the term 'seromucinous adenocarcinoma' is the more appropriate designation for non-ITAC. Squamoid morules in non-ITAC and SSH may be an immunophenotypic pitfall given the aberrant CDX2 expression.

Use of immunohistochemistry in the diagnosis of miscellaneous and metastatic tumors of the uterine corpus and cervix

Uncommon tumors in the uterus present diagnostic challenges. In some cases, the tumor subtype is usually seen outside the gynecologic tract and the possibility of a uterine primary is not considered. In other cases, histologic overlap with more common uterine tumors leads to potential misdiagnosis. Finally, metastatic carcinoma may involve the uterus and cervix. Rarely, symptoms related to the uterine metastasis may precede diagnosis of an extrauterine primary. Without the proper clinical context, the possibility of a missed diagnosis is increased. One must first be aware of these possibilities, but immunoperoxidase studies are often necessary to confirm the diagnosis. In this review, unusual and metastatic tumors involving the uterine corpus and cervix and immunoperoxidase studies used to diagnosis such tumors are discussed.

Among sinonasal tumors, CDX-2 immunoexpression is not restricted to intestinal-type adenocarcinomas

Intestinal-type adenocarcinoma (ITAC) is a rare form of sinonasal cancer characterized by an association with exposure to industrial dusts, aggressive clinical behavior, and histologic/immunophenotypic similarity to tumors of the gastrointestinal tract. ITAC is sometimes very poorly differentiated and difficult to distinguish from other sinonasal neoplasms, particularly in a limited biopsy. CDX-2 and cytokeratin 20 are consistently immunoreactive in ITAC and as a result, these immunostains are often used to support the diagnosis. However, CDX-2 and cytokeratin 20 have not been tested on a broad range of sinonasal tumors, so their specificities remain unknown. Immunohistochemistry for CDX-2 and cytokeratin 20 was performed on 6 sinonasal ITACs as well as 176 non-intestinal-type sinonasal neoplasms. CDX-2 and cytokeratin 20 were positive in all 6 cases of ITAC. CDX-2 immunoexpression was also observed in 17 of 176 (10 %) non-intestinal-type tumors including 6 of 16 (38 %) sinonasal undifferentiated carcinomas, 8 of 81 (10 %) squamous cell carcinomas (including 5 of 39 non-keratinizing variants), 2 of 20 (10 %) salivary-type adenocarcinomas, and 1 of 2 (50 %) small cell carcinomas. In contrast, among non-intestinal types of sinonasal tumors, cytokeratin 20 was only focally observed in 1 of 176 non-intestinal tumors (a non-keratinizing squamous cell carcinoma). All cases of non-intestinal surface-derived adenocarcinoma and esthesioneuroblastoma were negative for both markers. Both CDX-2 and cytokeratin 20 are highly sensitive for the diagnosis of sinonasal ITAC, but cytokeratin 20 is more specific. CDX-2 staining may be observed in other high grade tumor types, especially sinonasal undifferentiated carcinoma and non-keratinizing squamous cell carcinoma. As a result, in the setting of a poorly differentiated sinonasal carcinoma the diagnosis of ITAC should not be based on CDX-2 immunoexpression alone. Clear-cut glandular differentiation and cytokeratin 20 immunoexpression are more reliable features.

Molecular oncogenesis of craniopharyngioma: current and future strategies for the development of targeted therapies

Craniopharyngiomas are benign intracranial tumors that arise in the suprasellar and intrasellar region in children and adults. They are associated with calcification on neuroimaging, endocrinopathies, vision problems, and recurrence following subtotal resection. Molecular studies into their genetic basis have been limited, and therefore targeted medical therapies for this tumor have eluded physicians. With the discovery of aberrant Wnt/β-catenin pathway signaling in the pathogenesis of the most common subtype of craniopharyngioma (adamantinomatous), the identification of candidate genes and proteins implicated in this cascade provide attractive targets for future therapies. The recent development of a genetically engineered animal model of this tumor may also serve as a platform for evaluating potential therapies prior to clinical trials in humans. Advances in understanding the molecular pathogenesis of tumor recurrence have also been made, providing clues to develop adjuvant and neoadjuvant therapies to couple with tumor resection for optimal response rates. Finally, advances in genomic technologies and next-generation sequencing will underlie the translation of these genetic and molecular studies from the bench to clinical practice. In this review, the authors present an analysis of the molecular oncogenesis of craniopharyngioma and current directions in the development of novel therapies for these morbid, yet poorly understood brain tumors.

CDX-2 expression in malignant germ cell tumors of the testes, intratubular germ cell neoplasia, and normal seminiferous tubules

CDX-2 is a caudal-type homeobox gene, encoding a transcription factor that plays an important role in proliferation and differentiation of intestinal epithelial cells. The utility of antibodies to CDX2 in the identification of adenocarcinomas of the gastrointestinal tract, particularly colorectal adenocarcinomas, in both primary and metastatic settings is well established. It is well-known that patients with testicular tumors may occasionally lack an obvious palpable mass. However, the expression of CDX2 in malignant germ cell tumors of the testes which have metastatic potential has not been previously studied in a large series. A tissue microarray was constructed from 52 malignant germ cell tumors of the testes including: 29 cases of classic seminoma, 8 cases of embryonal carcinoma, 8 cases of yolk sac tumor, 4 cases of malignant teratoma, 2 cases of choriocarcinoma, and 1 case of spermatocytic seminoma. Ten cases of intratubular germ cell neoplasia and seven cases of benign testicles with normal seminiferous tubules were also included in tissue microarray. Immunohistochemical stains for CDX2 was performed and analyzed. Only nuclear staining was considered positive. Positive expression of CDX2 was identified in 2/2 cases (100 %) of choriocarcinoma, 4/8 cases (50 %) of teratoma, 3/8 cases (38 %) of embryonal carcinoma, 3/8 cases (38 %) of yolk sac tumor, and 1/29 cases (3 %) of classic seminoma. CDX2 was negative in all cases of intratubular germ cell neoplasia, normal seminiferous tubules, and the only case of spermatocytic seminoma. The role of CDX-2 in the differentiation of intestinal/enteric epithelial cells may contribute to the formation of trophoblastic, glandular, villous, or cystic structures in germ cell tumors of the testes. This study suggests that the expression of CDX2 in a variety of malignant germ cell tumors of the testes may be a potential pitfall in metastatic tumors of unknown primary, which are thought to be of gastrointestinal/colorectal origin but are actually from a clinically occult testicular tumor.

CDX2 as a marker for intestinal differentiation: Its utility and limitations

CDX2 is a nuclear homeobox transcription factor that belongs to the caudal-related family of CDX homeobox genes. The gene encoding CDX2 is a nonclustered hexapeptide located on chromosome 13q12-13. Homeobox genes play an essential role in the control of normal embryonic development. CDX2 is crucial for axial patterning of the alimentary tract during embryonic development and is involved in the processes of intestinal cell proliferation, differentiation, adhesion, and apoptosis. It is considered specific for enterocytes and has been used for the diagnosis of primary and metastatic colorectal adenocarcinoma. CDX2 expression has been reported to be organ specific and is normally expressed throughout embryonic and postnatal life within the nuclei of epithelial cells of the alimentary tract from the proximal duodenum to the distal rectum. In this review, the authors elaborate on the diagnostic utility of CDX2 in gastrointestinal tumors and other neoplasms with intestinal differentiation. Limitations with its use as the sole predictor of a gastrointestinal origin of metastatic carcinomas are also discussed.

Endometrial carcinomas: a review emphasizing overlapping and distinctive morphological and immunohistochemical features

This review focuses on the most common diagnostic pitfalls and helpful morphologic and immunohistochemical markers in the differential diagnosis between the different subtypes of endometrial carcinomas, including: (1) endometrioid versus serous glandular carcinoma, (2) papillary endometrioid (not otherwise specified, villoglandular and nonvillous variants) versus serous carcinoma, (3) endometrioid carcinoma with spindle cells, hyalinization, and heterologous components versus malignant mixed müllerian tumor, (4) high-grade endometrioid versus serous carcinoma, (5) high-grade endometrioid carcinoma versus dedifferentiated or undifferentiated carcinoma, (6) endometrioid carcinoma with clear cells versus clear cell carcinoma, (7) clear cell versus serous carcinoma, (8) undifferentiated versus neuroendocrine carcinoma, (9) carcinoma of mixed cell types versus carcinoma with ambiguous features or variant morphology, (10) Lynch syndrome-related endometrial carcinomas, (11) high-grade or undifferentiated carcinoma versus nonepithelial uterine tumors. As carcinomas in the endometrium are not always primary, this review also discusses the differential diagnosis between endometrial carcinomas and other gynecological malignancies such as endocervical (glandular) and ovarian/peritoneal serous carcinoma, as well as with extra-gynecologic metastases (mainly breast and colon).

Immunohistochemistry in the distinction between primary and metastatic ovarian mucinous neoplasms: Table 1

The distinction between a primary and metastatic mucinous carcinoma within the ovary may be problematic. In most cases, the distinction can be made by careful pathological examination encompassing both the gross and microscopic findings and taking into account the distribution of the disease. However, immunohistochemistry may be of value in certain scenarios. In this review, I discuss the value of markers in the distinction between primary ovarian mucinous neoplasms and metastatic mucinous carcinomas from the colorectum, appendix, pancreas, biliary tract, stomach and cervix, the most common primary sites which give rise to metastatic mucinous carcinoma within the ovary. There is a significant degree of immunophenotypic overlap between primary ovarian mucinous neoplasms and metastatic mucinous carcinomas from the gastrointestinal tract, especially the upper gastrointestinal type; this is because most primary ovarian mucinous carcinomas and borderline tumours are of so-called intestinal or enteric type and exhibit some degree of positivity with enteric markers. Mullerian type primary ovarian mucinous neoplasms also exist and exhibit distinct immunohistochemical differences to the more common intestinal type.

High-Grade Endometrial Carcinomas

High-grade endometrial carcinomas are a heterogeneous group of clinically aggressive tumors. They include FIGO grade 3 endometrioid carcinoma, serous carcinoma, clear cell carcinoma, undifferentiated carcinoma, and malignant mixed Müllerian tumor (MMMT). Epidemiologic, genetic, biologic prognostic and morphologic differences between these entities are striking in prototypic cases, yet substantial overlap exists and diagnostic criteria and therapeutic approaches that account for the group's diversity are currently insufficient. FIGO grade 3 endometrioid carcinoma demonstrates solid, trabecular or nested growth and may resemble poorly differentiated squamous cell carcinoma. Endometrioid glandular differentiation is usually focally present. Serous carcinoma usually displays papillary architecture but glandular and solid patterns may predominate. Tumor cells typically display diffuse and severe atypia. Clear cell carcinoma should be diagnosed by recognizing characteristic papillary or tubulocystic architecture with cuboidal tumor cells showing atypical but uniform nuclei. Cells with clear cytoplasm are frequently but not always present. On the other hand, clear cells may be encountered in endometrioid and serous carcinomas. Immunohistochemical stains for p53, p16, ER, PR, mib-1, hepatocyte nuclear factor 1β and pan-cytokeratin can be helpful in classifying these high-grade carcinomas. They should be used in concert with thorough morphologic examination, as part of a rational panel of markers and only in specific circumstances. Although these tumors may appear clinically and even morphologically similar, demographic and epidemiologic features as well as patterns of spread and treatment modalities differ.

CDX2 Expression in Yolk Sac Component of Testicular Germ Cell Tumors

CDX2 has been detected in the majority of colorectal adenocarcinoma cases and may be useful in determining the sites of origin of tumors. In this study, the authors evaluated CDX2 expression in germ cell tumors (GCTs) by immunohistochemistry. Forty cases of testicular GCTs and 8 cases of metastatic GCTs were retrieved for study. In the 40 cases of testicular GCTs, 13 were pure seminomas and 27 mixed GCTs. Yolk sac tumor (YST) was identified by morphology and glypican 3 staining in 20 testicular mixed GCTs. Of these 20 cases, 8 cases showed 1+ positivity for CDX2. Other primitive components of GCTs were negative. For the 6 cases of metastatic mixed GCT with YST, 4 cases were positive, 2+ in 2 cases and 1+ in 2 cases. The positivity of CDX2 in GCTs warrants including YST in the differential diagnosis of adenocarcinoma of unknown origin.

Pathologic evaluation of unknown primary cancer

The pathologic approach to metastases of unknown primary cancer (UPC) is stepwise and uses the clinical context, morphology, and, where necessary, immunohistochemistry (IHC). This review covers the initial approach to a UPC biopsy; the diagnosis of malignancy and broad tumor typing into carcinoma, melanoma, lymphoma, or sarcoma; and further subtyping of carcinoma into germ cell (broadly included), squamous, neuroendocrine, and solid organ including liver and renal, and adenocarcinomas. Finally, for adenocarcinoma, the prediction of primary tumor site, including lung, pancreas, stomach, colon, ovary, prostate, and breast, is discussed. For each tumor type, the morphologic features are presented alongside established useful IHC markers, with a description of their staining patterns and common diagnostic dilemmas. Optimal tissue handling and IHC interpretation, quality assurance, and limitations also are discussed. The target readership is oncologists, but other clinicians and trainee pathologists also may find the content of use.

Aberrant expression of an "intestinal marker" Cdx2 in pyloric gland adenoma of the gallbladder

The aim of this study was to survey Cdx2 expression in pyloric gland adenoma (PGA) of the gallbladder. We reviewed 29 PGA cases, ten (34.4%) and seven (24.1%) of which showed intestinal metaplasia (IM) and squamous morule (SM), respectively. The immunostaining for Cdx2, beta-catenin, MUC5AC, MUC2, MUC6, and M-GGMC-1 was performed and scored (0 = negative, 1+ = <10%, 2+ = 10% to <30%, 3+ = 30% to <50%, 4+ = 50% to <70%, 5+ = 70-100%). Although its scores were relatively low (1+ or 2+), Cdx2 was frequently expressed in 27 cases (93.1%). Not only goblet and/or Paneth cells were positive but also non-IM cells in PGAs, as opposed to the lack of staining in the background mucosa. Cdx2 scores were not correlated with those of IM (p = 0.485) and MUC2 (p = 0.868). Of note, Cdx2 was positive in foci of SM in all seven cases, and there was a significant difference in Cdx2 scores between PGAs with and without SM. Furthermore, the p value of scores between Cdx2 and beta-catenin was 0.051, and both mean labeling indices (LIs) were correlated (r = 0.736). With Cdx2, higher morular LIs than glandular LIs were observed (p = 0.001). Finally, we concluded that aberrant Cdx2 expression in PGAs is closely associated with nuclear beta-catenin expression and SM in contrast with IM.