Performance of breast fine needle aspiration as an initial diagnostic tool: A large academic hospital experience.

BACKGROUND: The clinical performance of the Yokohama reporting system for breast cytology remains uncertain. METHODS: In this study, we retrospectively evaluated 318 breast fine needle aspirations (FNABs) from Los Angeles County Hospital over a five-year period, analysing data for breast cytology, histology, and radiology. RESULTS: Among 318 breast FNAB cases, 78.3% (249/318) were benign and 5.3% (17/318) malignant. Of 83 cases with follow-up histology, 14.5% (12/83) were insufficient, 66.3% (55/83) were benign, and 16.9% (17/83) were malignant. Of 55 benign cases, 61.8% (34/55) were fibroadenoma and 9 (9/55, 16.4%) were fibrocystic changes. Two cases were diagnosed as "atypical" but confirmed "benign" on core needle biopsy (CNB). No "suspicious" cases were found. Seventeen malignant cases were confirmed by CNB, including 70.6% (12/17) invasive ductal carcinoma, 11.8% (2/17) invasive lobular carcinoma, and one malignant phyllodes tumour. Receptor studies on cell blocks of three malignant cases showed concordant results with CNB results. In addition, 82.2% (148/180) of lesions with Breast Imaging-Reporting and Data System (BI-RADS) scores of 2 or 3 were benign and 92.3% (12/13) BI-RADS score 5 lesions were malignant on FNAB. Finally, 90% (67/74) of BI-RADS 4a lesions were benign, and 97% (36/37) of fibroadenomas were BI-RADS score 4a. CONCLUSION: This, by far the largest U.S. breast cytology study, showed 93.3% sensitivity, 100% specificity, 100% positive predictive value, and 98.2% negative predictive value for breast FNAB. Women with breast lesions of BI-RADS score 3 or less have a low risk of malignancy; FNAB would contribute to the reduction of excisional biopsies. FNAB can be considered as an initial diagnostic tool for BI-RADS 4 mass/lesions and satellite lesions, as well as for triaging patients.

Enhancing the Pipeline of Pathologists in the United States.

The shortage of pathologists in the United States has been a topic of discussion for the past 2 decades. At the 2014 Association of Pathology Chairs (APC)/Program Directors Section (PRODS) meeting, a Pipeline Subcommittee (PSC) of the APC Advocacy Committee was formed with the charge of investigating ways to increase the number of highly qualified United States Medical Graduates entering into pathology. Several online surveys were developed to identify the strengths, weaknesses, opportunities, and threats to recruitment into pathology. Two general pipeline surveys were completed; one was issued in 2014 and is discussed in this article. In 2018, the Medical Education Working Group surveyed the Undergraduate Medical Education Directors Section on the state of undergraduate medical education for pathology; pipeline issues are included in this article from the 2018 survey. Medical schools that reported 2% to 5% or more of their graduates going into pathology were compared with schools where less than 1% went into pathology. About one-third of schools producing more pathology residents had Post-Sophomore Pathology Fellowships. Schools that had a faculty member on the curriculum committee that felt they had little or no control were more likely to have fewer graduates going into pathology. Schools having students view an autopsy as a requirement of graduation were more likely to produce graduates going into pathology. However, none of these characteristics achieved statistical significance. Continued incorporation of best practices for exposure of pathology as a medical specialty as well as outreach to students will be necessary for the future pipeline.

ACGME Milestones 2.0: why and what's new for cytopathology?

BACKGROUND: Primary stakeholders in the Accreditation Council for Graduate Medical Education (ACGME) Milestones Project are: ACGME, Residency Programs, Residents, Fellowship Programs, Fellows, and Certification Boards. The intent of the Milestones is to describe the educational and professional developmental trajectory of a trainee from the first stages of their postgraduate education through the completion of their clinical training. The Milestones 2.0 project includes changes made based on experience with Milestones 1.0. METHODS: The ACGME solicited volunteers to participate in the development of subspecialty Milestones 2.0. The workgroup was charged with reviewing/making any additions to the four "Harmonized Milestones", developing subspecialty specific milestones for the Patient Care and Medical Knowledge competencies, and creating a supplemental guide. The Milestones were finalized following review of input from an open comment period. RESULTS: The Cytopathology Milestones 2.0 will go into effect July 2021. They include additional subcompetencies in the 4 harmonized competency areas and cytopathology-specific edits to the patient care and medical knowledge subcompetencies. Although the number of subcompetencies has increased from 18 to 21, within each subcompetency, the number of milestone trajectories has decreased. Additionally, within each subcompetency, the wording has been streamlined. A supplemental guide was created and Milestones 1.0 were compared to 2.0; however, curriculum mapping has been left to programs to develop. CONCLUSIONS: The ultimate goal of the Cytopathology Milestones 2.0 is to provide better real-time documentation of the progress of cytopathology fellows. The expected outcome is to produce highly competent cytopathologists, improving the care they provide, regardless of the program at which they trained.

Entry of Graduates of US Pathology Residency Programs Into the Workforce: Cohort Data Between 2008 and 2016 Remain Positive and Stable.

The pathologist workforce in the United States is a topic of interest to the health-care community as a whole and to institutions responsible for the training of new pathologists in particular. Although a pathologist shortage has been projected, there has been a pervasive belief by medical students and their advisors that there are "no jobs in pathology." In 2013 and again in 2017, the Program Directors Section of the Association of Pathology Chairs conducted surveys asking pathology residency directors to report the employment status of each of their residents graduating in the previous 5 years. The 2013 Program Directors Section survey indicated that 92% of those graduating in 2010 had obtained employment within 3 years, and 94% of residents graduating in 2008 obtained employment within 5 years. The 2017 survey indicated that 96% of those graduating in 2014 had obtained employment in 3 years, and 97% of residents graduating in 2012 obtained positions within 5 years. These findings are consistent with residents doing 1 or 2 years of fellowship before obtaining employment. Stratification of the data by regions of the country or by the size of the residency programs does not show large differences. The data also indicate a high percentage of employment for graduates of pathology residency programs and a stable job market over the years covered by the surveys.

Report and Recommendations of the Association of Pathology Chairs' Autopsy Working Group.

Autopsy has been a foundation of pathology training for many years, but hospital autopsy rates are notoriously low. At the 2014 meeting of the Association of Pathology Chairs, some pathologists suggested removing autopsy from the training curriculum of pathology residents to provide additional months for training in newer disciplines, such as molecular genetics and informatics. At the same time, the American Board of Pathology received complaints that newly hired pathologists recently certified in anatomic pathology are unable to perform an autopsy when called upon to do so. In response to a call to abolish autopsy from pathology training on the one hand and for more rigorous autopsy training on the other, the Association of Pathology Chairs formed the Autopsy Working Group to examine the role of autopsy in pathology residency training. After 2 years of research and deliberation, the Autopsy Working Group recommends the following:Autopsy should remain a component of anatomic pathology training.A training program must have an autopsy service director with defined responsibilities, including accountability to the program director to record every autopsy performed by every resident.Specific entrustable activities should be defined that a resident must master in order to be deemed competent in autopsy practice, as well as criteria for gaining the trust to perform the tasks without direct supervision.Technical standardization of autopsy performance and reporting must be improved.The current minimum number of 50 autopsies should not be reduced until the changes recommended above have been implemented.

Identifying the Challenges of "Small" Pathology Residency Programs and Creating Collaborative Solutions.

The majority of pathology residency training programs in the United States are considered to be small training programs. Small training programs, regardless of specialty, encounter unique challenges that have been documented in the literature. With the implementation of the Next Accreditation System (NAS), and other Accreditation Council for Graduate Medical Education (ACGME) Common Program Requirements, adequate personnel and other resources are necessary. An online survey was conducted on the pathology program directors' section listserv to help identify characteristics and challenges of small pathology residency training programs. A discussion group on small pathology residency programs was held at the 2015 Association of Pathology Chairs/Program Directors annual meeting, where the results of the survey were discussed and small breakout groups followed the discussion of the survey. The results of the online survey and discussion groups are discussed in this paper.

The Pathologist Pipeline: Implications of Changes for Programs and Post-Sophomore Fellowships-Program Directors' Section Perspective.

A shortage of physicians in the United States has been long projected. Because of predictions of retirement among the aging pathology workforce, there is an anticipated shortage of pathologist as well. To address the pathology workforce shortage among pathologists, the Association of Pathology Chairs assembled a subcommittee of the Association of Pathology Chairs Advocacy Committee to explore ways to identify the strengths, weaknesses, opportunities, and threats to the pathology workforce. One opportunity to encourage strong candidates to pursue pathology as a career is to explore possibility to revisit advanced credit for the post-sophomore fellowship. A survey that was designed to understand the post-sophomore fellowship training better was distributed on the listserv of the Program Directors Section of the Association of Pathology Chairs. A review of the literature on post-sophomore fellowship programs is presented in light of the findings from this survey. Many post-sophomore fellowship programs are run similar to a first-year resident experience, although programs show great diversity in curriculum, including some programs that focus on research. Post-sophomore fellowships attract medical students to the area of pathology and tend to end up in academic and research positions. A second survey of program directors served as an opinion poll of challenging issues that affect residency training. From the second opinion poll, most program directors feel that residents can use additional training to improve the outcome of our future pathologists.

Evolution of the Pathology Residency Curriculum: Preparing for a Positive Future.

The required medical knowledge and skill set for the pathologist of 2020 are different than in 2005. Pathology residency training curriculum must accordingly change to fulfill the needs of these ever-changing requirements. In order to make rational curricular adjustments, it is important for us to know the current trajectory of resident training in pathology-where we have been, what our actual current training curriculum is now-to understand how that might change in anticipation of meeting the needs of a changing patient and provider population and to fit within the evolving future biomedical and socioeconomic health-care setting. In 2013, there were 143 Accreditation Council for Graduate Medical Education-accredited pathology residency training programs in the United States, with approximately 2400 residents. There is diversity among residency training programs not only with respect to the number of residents but also in training venue(s). To characterize this diversity among pathology residency training programs, a curriculum survey was conducted of pathology residency program directors in 2013 and compared with a similar survey taken almost 9 years previously in 2005 to identify trends in pathology residency curriculum. Clinical pathology has not changed significantly in the number of rotations over 9 years; however, anatomic pathology has changed dramatically, with an increase in the number of surgical pathology rotations coupled with a decline in stand-alone autopsy rotations. With ever-expanding medical knowledge that the graduating pathology resident must know, it is necessary to (1) reflect upon what are the critical need subjects, (2) identify areas that have become of lesser importance, and then (3) prioritize training accordingly.

Diagnosis of Basal-Like Breast Cancer Using a FOXC1-Based Assay.

BACKGROUND: Diagnosis of basal-like breast cancer (BLBC) remains a bottleneck to conducting effective clinical trials for this aggressive subtype. We postulated that elevated expression of Forkhead Box transcription factor C1 (FOXC1) is a simple and accurate diagnostic biomarker for BLBC. METHODS: Accuracy of FOXC1 expression in identifying BLBC was compared with the PAM50 gene expression panel in gene expression microarray (GEM) (n = 1992) and quantitative real-time polymerase chain reaction (qRT-PCR) (n = 349) datasets. A FOXC1-based immunohistochemical (IHC) assay was developed and assessed in 96 archival formalin-fixed, paraffin-embedded (FFPE) breast cancer samples that also underwent PAM50 profiling. All statistical tests were two-sided. RESULTS: A FOXC1-based two-tier assay (IHC +/- qRT-PCR) accurately identified BLBC (AUC = 0.88) in an independent cohort of FFPE samples, validating the accuracy of FOXC1-defined BLBC in GEM (AUC = 0.90) and qRT-PCR (AUC = 0.88) studies, when compared with platform-specific PAM50-defined BLBC. The hazard ratio (HR) for disease-specific survival in patients having FOXC1-defined BLBC was 1.71 (95% CI = 1.31 to 2.23, P < .001), comparable to PAM50 assay-defined BLBC (HR = 1.74, 95% CI = 1.40 to 2.17, P < .001). FOXC1 expression also predicted the development of brain metastasis. Importantly, unlike triple-negative or Core Basal IHC definitions, a FOXC1-based definition is able to identify BLBC in both ER+ and HER2+ patients. CONCLUSION: A FOXC1-based two-tier assay, by virtue of being rapid, simple, accurate, and cost-effective may emerge as the diagnostic assay of choice for BLBC. Such a test could substantially improve clinical trial enrichment of BLBC patients and accelerate the identification of effective chemotherapeutic options for this aggressive disease.

Cytopathology fellowship milestones.

The American Society of Cytopathology has provided guidelines for goals and objectives for cytopathology fellows. There are 90 Accreditation Council for Graduate Medical Education-accredited cytopathology fellowship training programs in the United States, each with its own unique curriculum designed to achieve these goals and objectives. The Accreditation Council for Graduate Medical Education cytopathology fellowship milestones were developed to ensure some uniformity in the outcomes of the various skill sets and competencies expected of a graduating cytopathology fellow. The rationale, development, and details of the cytopathology fellowship milestones are described herein.

Selective pathology fellowships: diverse, innovative, and valuable subspecialty training.

CONTEXT: Although selective pathology fellowships have a long-standing history of developing trainees with advanced expertise in specific areas of pathology other than those of the American Board of Pathology-certified subspecialties, the widespread interest in this training continues to grow. OBJECTIVE: To describe the historical background and current status of selective pathology fellowships, and to provide examples of 3 programs. In addition, Accreditation Council for Graduate Medical Education (ACGME)-accredited programs and nonaccredited programs in Selective Pathology are compared. DATA SOURCES: ACGME data banks and publicly available online materials were used. Program directors of the fellowships examples in this paper provided program-specific information. Additionally, an online survey of the program directors and program coordinators of ACGME-accredited programs and nonaccredited programs in selective pathology was performed. CONCLUSIONS: There are currently 76 ACGME-accredited selective pathology programs. The programs are distributed between 3 major categories: surgical pathology, focused anatomic pathology, and focused clinical pathology. Although the vast majority of programs are concerned that their funding source may be cut in the next 3 years, most programs will not change the number of fellowship positions in their programs. Program requirements devoted specifically and solely to selective pathology have been developed and are in effect. The value of this training is recognized not only by pathologists, but by clinicians as well, in both academia and private practice. Importantly, the diversity and innovation inherent in selective pathology allow these programs to adeptly address new subspecialty areas and technologic advances in the current and evolving practice of pathology.

The pathology milestones and the next accreditation system.

CONTEXT: In the late 1990s, the Accreditation Council for Graduate Medical Education developed the Outcomes Project and the 6 general competencies with the intent to improve the outcome of graduate medical education in the United States. The competencies were used as the basis for developing learning goals and objectives and tools to evaluate residents' performance. By the mid-2000s the stakeholders in resident education and the general public felt that the Outcomes Project had fallen short of expectations. OBJECTIVE: To develop a new evaluation method to track trainee progress throughout residency using benchmarks called milestones. A change in leadership at the Accreditation Council for Graduate Medical Education brought a new vision for the accreditation of training programs and a radically different approach to the evaluation of residents. DATA SOURCES: The Pathology Milestones Working Group reviewed examples of developing milestones in other specialties, the literature, and the Accreditation Council for Graduate Medical Education program requirements for pathology to develop pathology milestones. The pathology milestones are a set of objective descriptors for measuring progress in the development of competency in patient care, procedural skill sets, medical knowledge, practice-based learning and improvement, interpersonal and communication skills, professionalism, and systems-based practice. CONCLUSIONS: The milestones provide a national standard for evaluation that will be used for the assessment of all residents in Accreditation Council for Graduate Medical Education-accredited pathology training programs.

Anatomic and clinical pathology boot camps: filling pathology-specific gaps in undergraduate medical education.

CONTEXT: The Liaison Committee on Medical Education began an initiative to change medical education across the United States in the early 2000s. With the explosion in medical science knowledge, the need arose to teach selected fundamental information both in a contextual and in an active learning manner. OBJECTIVE: To identify ways to address gaps in training and knowledge that became apparent following implementation of learner-centered teaching methods, with devotion of more time to Internet-based learning and less emphasis on face-to-face lecture time. There was a dramatic departure from or de-emphasis of many traditional courses, such as embryology, gross anatomy, microscopic anatomy, and pathology, to the integration of these sciences into system-based active learning courses. This change in medical school curricula produces a medical graduate who hopefully thinks differently but certainly lacks subject-specific knowledge for a variety of medical specialties. DATA SOURCES: Pathology residency programs have developed "boot camps" for the initial months of residency training both to provide the necessary foundation of pathology-specific medical science and to introduce basic skills and processes required for practice of anatomic pathology and laboratory medicine. The College of American Pathologists Graduate Medical Education Committee sent a questionnaire out on the Program Directors Section Listserv; the results are discussed and 3 boot camp programs are described. CONCLUSIONS: Boot camps have 2 purposes: (1) to teach or strengthen knowledge required to practice pathology and (2) to introduce basic skills and processes that will be used during the practitioner's career.

Phlegmonous gastritis in a patient with myeloid sarcoma: a case report.

Phlegmonous gastritis is a rare acute bacterial infection of the gastric wall with an extremely high mortality rate. Early diagnosis is crucial for immediate treatment that could improve the outcomes. Here we report a case in which a patient with underlying chronic myelomonocytic leukemia was diagnosed with phlegmonous gastritis on biopsy. This 57-year-old man presented with shortness of breath and intermittent upper quadrant abdominal pain for 4 days. Laboratory tests showed markedly increased white blood cell. A diagnosis of chronic myelomonocytic leukemia was made based on a peripheral blood smear and flow cytometry. Gastric biopsy showed suppurative inflammation in the submucosal region, prompting the diagnosis of phlegmonous gastritis. The patient was given empirical antibiotic treatment, and the white blood cell decreased dramatically. Surgical intervention was discussed but deferred. Despite continued antibiotics treatment, the patient died. The limited autopsy confirmed the diagnosis of phlegmonous gastritis. Immunohistochemical studies further revealed the occurrence of myeloid sarcoma that involved the gastrointestinal tract.

Unmethylated E-cadherin gene expression is significantly associated with metastatic human prostate cancer cells in bone.

BACKGROUND: The concurrent determination of methylation status of E-cadherin gene and E-cadherin protein expression remains scant in metastatic prostate cancer cells in bone, the most prevalent site for metastatic growth. Therefore, the study was undertaken to ascertain the methylation status of E-cadherin gene, a most frequent and known epigenetic mechanism of its regulation, and the protein expression in prostate tissue biopsy specimen. METHODS: The methylation of E-cadherin gene was determined by methylation specific-PCR and the protein expression by immunohistochemical method in the consecutive sections of each prostate tissue biopsy specimen. RESULTS: The unmethylated E-cadherin gene and homogeneous E-cadherin protein expression was significantly associated with BPH as compared to the primary prostate carcinoma (Fisher's Exact P < 0.001). A significant association was observed between the concurrent methylated gene and markedly reduced expression of the protein in the primary prostate cancer cells as compared to the BPH cells, suggesting methylation-dependent regulation of the gene expression in these cases. In contrast to the primary cancer, a highly significant increase in the frequency of metastatic prostate cancer cells in bone exhibited the concurrent expression of unmethylated gene and homogeneous protein (Fisher's Exact P < 0.001). CONCLUSIONS: The study clearly demonstrated a significant association of the concurrent expression of unmethylated E-cadherin gene and E-cadherin protein with metastatic prostate cancer cells in bone, and that its expression may have a role in the intercellular adhesion in the formation of metastatic lesions in bone.

Overexpression of E-cadherin and beta-catenin proteins in metastatic prostate cancer cells in bone.

BACKGROUND: The expression of E-cadherin in the intercellular adhesion of metastatic prostate cancer cells in bone, which is the most prevalent site of metastatic growth, remains elusive. METHODS: The aim of the study was to compare the concurrent membranous expression of E-cadherin and beta-catenin proteins, the state which is known to be associated with the cellular adhesion function of E-cadherin, in prostate biopsy tissue specimens by immunohistochemical staining method. The expression patterns of E-cadherin or beta-catenin were classified as homogeneous (most cells exhibiting positively), heterogeneous (a few scattered patches of cells with positivity) or negative. RESULTS: Benign prostate hyperplasia cells exhibited homogeneous expression of both E-cadherin and beta-catenin in 9 of 11 (82%), whereas the primary prostate cancer cells were homogeneously positive for both proteins only in 4 of 22 (18%) of the cases. The results are similar to those reported in literature. However, in contrast to the primary cancer, a significantly increased frequency of the metastatic prostate cancer cells in bone exhibited homogeneous expression of E-cadherin and beta-catenin in 12 of 17 (71%) of the cases. A statistically significant association was observed between the overexpression of both proteins and the metastatic prostate cancer cells in bone (Fisher's exact P < 0.001). CONCLUSIONS: The result of the study demonstrated for the first time that the membranous overexpression of E-cadherin and beta-catenin are significantly associated with the metastatic prostate cancer cells in bone and that the high frequency of expression suggest their involvement in the intercellular adhesion of the metastatic cells in bone.

Telomerase and markers of cellular proliferation are associated with the progression of cervical intraepithelial neoplasia lesions.

The expression of the catalytic subunit of telomerase protein (human telomerase reverse transcriptase [hTERT]), which is associated with telomerase activity, was evaluated as a potential marker of the high-grade premalignant cervical intraepithelial neoplasia (CIN 2/3) lesions. For comparison, cases of normal cervical squamous mucosa, low-grade CIN1 lesion, and cervical squamous cell carcinoma were included. The hTERT expression was also compared with Ki-67 and topoisomerase II-alpha (TPII-alpha) to determine the proliferative activity of the hTERT-positive dysplastic cells by a quantitative immunohistochemical staining method and was classified as follows: negative, 5% or less; moderate, 6% to 50%; or high, greater than 50% of the positive cells. The hTERT-positive cells were detected in a patchy pattern in the lower parabasal layers and in much of the basal layer in normal squamous mucosa. A similar frequency of Ki-67- or TPII-alpha-positive cells was observed, with the exception of the basal layer cells that were mostly negative. It is worthy to note that the recognizable intact basal layer cells in cases of CIN lesions were also consistently positive for the expression of hTERT, but rarely for Ki-67 or TPII-alpha. The expression of hTERT was detected in a less patchy pattern at a high or moderate percentage of the dysplastic epithelial cells each in 28.5% of cases of CIN1 lesions. A similar frequency, high and moderate percentage combined, of the TPII-alpha-positive dysplastic cell was also observed. In contrast, a high percentage of the hTERT-positive dysplastic cells were detected as diffuse basal or full-length thickness in 87.5% or 95% of cases of CIN2 or CIN3, respectively. A similar frequency of Ki-67 or TPII-alpha expression was observed in the dysplastic cells of CIN3 lesions. The pattern of hTERT-positive malignant cells in squamous cell carcinoma and dysplastic cells in the high-grade CIN lesions, to a greater extent, and dysplastic cells in the low-grade CIN lesion, to a lesser extent, was distinct from that of the normal cervical squamous mucosa. The results suggest that the progressive increase in the hTERT expression, together with the proliferative activity of the dysplastic epithelial cells of the high-grade CIN lesions, represents an early genetic abnormality in cervical pathogenesis.

The autopsy as a performance measure and teaching tool.

A survey of pathology training programs about current operations and attitudes revealed that the autopsy is underused in medical student and pathology resident teaching, is inadequately reported, often does not have a dedicated faculty, is not championed by pathologists or clinicians, is not valued as a performance measure, and is barely used as a resource for medical research. The autopsy can be reestablished as a teaching tool and performance measure, but this will require that the autopsy be recognized as a credible and valuable medical procedure. The autopsy must then be funded; and new sources of both volume and funding, such as incorporating autopsies into payment schedules, into clinical trials, and in pay-for-performance initiatives, must be solicited. Once there is reimbursement for autopsies, pathologists, clinicians, and health care administrators will embrace the autopsy as a new source of revenue and as a valid measure of physician, hospital, and health system performance. Pathologists and the pathology specialty societies must take the lead in the reestablishment of the autopsy and must, at the same time, encourage innovations such as centralization, greater use of Pathology Assistants, and application of molecular techniques. New tools for using the autopsy in medical student teaching should be embraced, and the role of the autopsy in pathology residency programs must be reevaluated.

Overexpression of E-cadherin protein in metastatic breast cancer cells in bone.

AIM: The aim of the present study was to evaluate E-cadherin, whose expression remains poorly understood in the intercellular adhesion of metastatic breast cancer cells in bone, the most prevalent site for metastatic growth. MATERIALS AND METHODS: An immunohistochemical staining method was used for the localization of E-cadherin protein in tissue biopsy specimens of normal breast (n = 9) and well- (n = 8), moderately (n = 8) or poorly (n = 14) differentiated invasive primary breast cancer and metastatic breast cancer in bone (n = 17). The expression patterns of E-cadherin were classified as homogeneous (most cells exhibiting positivity), heterogeneous (a few scattered patches of cells with positivity) or negative (cells with undetectable positivity). RESULTS: Normal breast epithelial cells showed homogeneous overexpression of E-cadherin in all cases. A progressive and statistically significant reduction of E-cadherin expression was detected in the histologically well- to moderately to poorly differentiated breast cancer cells (p < 0.001). The clumps of invasive primary breast cancer cells in CD-31-positive blood vessels exhibited E-cadherin expression. Moreover, as compared to the poorly differentiated breast cancer cells, a significantly increased frequency of the metastatic breast cancer cells in bone exhibited homogeneous expression of E-cadherin in 15 out of 17 and heterogeneous expression in the remaining 2 cases (McNemar Exact p < 0.001). This is the first demonstration of membranous overexpression of E-cadherin on metastatic breast cancer cells in bone; the high frequency of its expression may have a role in the intercellular adhesion of metastatic cells in bone.