Mammary Intraepithelial Neoplasia: A Translational Classification System for the Intraductal Epithelial Proliferations

Is it Time to Retire the Term of Low-Grade Ductal Carcinoma in Situ and Replace it With Ductal Neoplasia?

As the leading cause of cancer morbidity and the second leading cause of cancer mortality among women, breast cancer continues to remain a major global public health problem. Consequently, significant attention has been directed toward early breast cancer detection and prevention. As a result, the number of image-detected biopsies has increased, and minimally invasive diagnostic procedures have almost replaced open surgical biopsies. Therefore, pathologists are expected to provide more information with less tissue and diagnose increasing numbers of atypical proliferative breast lesions, in situ lesions, and small breast carcinomas. This is a difficult task, as reflected by continuous reports highlighting the challenges associated with morphologic distinction between atypical ductal hyperplasia and low-grade ductal carcinoma in situ. The current interobserver variability among pathologists to accurately define these two entities often leads to silent overdiagnosis and overtreatment. Up to now, there are no reproducible morphologic features and/or any reliable biomarkers that can accurately separate the above-mentioned entities. Despite these reports, patients diagnosed with low-grade ductal carcinoma in situ are subject to cancer therapy regardless of the fact that low-grade ductal carcinoma in situ is known to be an indolent lesion. Studies have shown that low and high-grade ductal carcinoma in situ are genetically different forms of breast cancer precursors; however, the term ductal carcinoma in situ is followed by cancer therapy regardless of the grade and biology of the tumor. In contrast, patients with the diagnoses of atypical ductal hyperplasia do not undergo cancer therapy. In the current article, attempts are made to highlight the continuous dilemma in distinction between atypical ductal hyperplasia and low-grade ductal carcinoma in situ. Going forward, we suggest that low-grade ductal carcinoma in situ be referred to as ductal neoplasia. This alternative terminology allows for different management and follow-up strategies by eliminating the word carcinoma.

"Borderline" epithelial lesions of the breast: what have we learned in the past three decades?

Atypical ductal hyperplasia (ADH), atypical lobular hyperplasia (ALH) and flat epithelial atypia (FEA) are common lesions mainly detected during mammographic screening. They are considered lesions at risk for the development of breast cancer, and they have been documented as non-obligate precursors of low grade in situ carcinomas. In a monumental work in 1991 Rosai gathered them as “borderline epithelial lesions”, and he described and demonstrated the subjectivity in their microscopic interpretation. Such subjectivity persists nowadays and limits considerably the diagnostic consistency. With his incredible ability to see, analyze and rationalize, Rosai introduced the concept of “mammary intraepithelial neoplasia (MIN) of either ductal or lobular type, followed by a grading system” which would have better represented the biological continuum between these lesions and benign and malignant lesions.

Quantitative nucleic features are effective for discrimination of intraductal proliferative lesions of the breast

Background:

Intraductal proliferative lesions (IDPLs) of the breast are recognized as a risk factor for subsequent invasive carcinoma development. Although opportunities for IDPL diagnosis have increased, these lesions are difficult to diagnose correctly, especially atypical ductal hyperplasia (ADH) and low-grade ductal carcinoma in situ (LG-DCIS). In order to define the difference between these lesions, many molecular pathological approaches have been performed. However, still we do not have a molecular marker and objective histological index about IDPLs of the breast.

Methods:

We generated full digital pathology archives from 175 female IDPL patients, including usual ductal hyperplasia (UDH), ADH, LG-DCIS, intermediate-grade (IM)-DCIS, and high-grade (HG)-DCIS. After total 2,035,807 nucleic segmentations were extracted, we evaluated nuclear features using step-wise linear discriminant analysis (LDA) and a support vector machine.

Results:

High diagnostic accuracy (81.8–99.3%) was achieved between pathologists’ diagnoses and two-group LDA predictions from nucleic features for IDPL discrimination. Grouping of nuclear features as size and shape-related or intranuclear texture-related revealed that the latter group was more important when distinguishing between normal duct, UDH, ADH, and LG-DCIS. However, these two groups were equally important when discriminating between LG-DCIS and HG-DCIS. The Mahalanobis distances between each group showed that the smallest distance values occurred between LG-DCIS and IM-DCIS and between ADH and Normal. On the other hand, the distance value between ADH and LG-DCIS was larger than this distance.

Conclusions:

In this study, we have presented a practical and useful digital pathological method that incorporates nuclear morphological and textural features for IDPL prediction. We expect that this novel algorithm is used for the automated diagnosis assisting system for breast cancer.

Intraductal proliferative lesions of the breast-terminology and biology matter: premalignant lesions or preinvasive cancer?

Morphological criteria for the diagnosis of intraductal proliferative lesions of the breast have been an object of research and much controversy, and its terminology is rather confusing. Knowledge of the molecular aspects of this disease probably necessitates further research to clarify if these entities can be identified as breast cancer precursors or as a malignant preinvasive disease. These issues are of great interest not only for their biological implications, but also to the clinician who must understand the disease and direct therapies. Molecular studies have shown that epitheliosis (usual ductal hyperplasia) is not monoclonal, while malignant lesions (atypical ductal hyperplasia, flat epithelial atypia, low-grade and high-grade intraductal carcinoma) constantly show these characteristics. These malignant lesions, classified with a DIN grading system (ductal intraepithelial neoplasia), are not obligate precursors of invasive ductal carcinoma and do not represent different evolving grades in a linear model of cancerogenesis. Breast cancerogenesis probably has different pathways with different morphologic precursors.

Protein biomarkers for breast cancer prevention

Protein biomarkers suitable for the prevention of breast cancer must be extremely sensitive, easily detectable and highly correlated with the disease. They should be expressed in the reversible phase of carcinogenesis. Among the large number of candidate tumour-associated proteins, those related to the oestrogen/chorionic gonadotropin/insulin pathway seem to be of most interest because these can be causally implicated. They presumably are the first to express differently and are open to hormonal treatments. The biomarkers that give information on membrane receptor-modulated signal transduction should be considered as well. Up to now, only tamoxifen has shown some preventive activity, suggesting that the oestrogen pathway is useful indeed. Fenretinide and recombinant human chorionic gonatotropin (hCG) are also promising. But the financial requirements and the very long assessment periods largely prevent current research. This is precisely why we badly need to give priority to molecular biology research, in particular in the protein compartment There is widespread belief that advanced proteomics together with increased informatics can provide specific combinations of disease-related expression profiles that could identify high-risk groups with much more reliability and allow us to monitor preventive strategies.

Combined E-cadherin and high molecular weight cytokeratin immunoprofile differentiates lobular, ductal, and hybrid mammary intraepithelial neoplasias

The terminal duct-lobular unit is the origin of 2 distinct variants of intraepithelial neoplasia traditionally separated into ductal and lobular types based on a combination of cytologic and architectural features. In general, distinction of the fully developed or classic lobular intraepithelial neoplasia (LIN) from various grades of ductal intraepithelial neoplasia (DIN) is not a problem. An increasing number of lesions that appear to have intermediate, overlapping ductal and lobular features are being sent to us for consultation because of the distinctly different clinical implication of the 2 diagnoses. We have separated and designated these as MIN (mammary intraepithelial neoplasia, not otherwise specified), whereas others have categorized them into either a definitive ductal or lobular subtype. The recent findings that LIN lacks immunoreaction for E-cadherin coupled with significantly diminished to absent expression of the high molecular weight (HMW) cytokeratins in more than 90% of grade 1b or higher DIN prompted us to evaluate intraepithelial neoplasias for a possibly more precise immunohistochemical categorization. One hundred and ten examples of intraepithelial neoplasias, consisting of 40 classic LIN, 20 unequivocal DIN 1c to DIN 3 (ductal carcinoma in situ), and 50 MIN, were acquired from the files of the Armed Forces Institute of Pathology. These specimens were tested with an antibody to E-cadherin and with antibody 34ssE12 reactive against HMW cytokeratins 1, 5, 10 and 14. All samples of LIN showed complete absence of reactivity with anti-E-cadherin, whereas all cases of DIN displayed a positive immunoreaction. In contrast, the DIN lesions displayed little or no reactivity with 34ssE12, whereas the lobular lesions showed cytoplasmic reactivity, often in a distinct perinuclear pattern. Twenty-three of the morphologically indeterminate cases could be classified as either ductal or lobular based on the immunoprofile, and 27 demonstrated an immunoprofile that differed from either typical DIN or classic LIN. Among the 27 MIN, 11 were negative for both markers (negative hybrids), whereas 16 were positive for both markers (positive hybrids). These 2 antibodies in combination are extremely useful in distinguishing lobular and ductal lesions and clarifying the nature of some of the morphologically intermediate cases. Also, they have confirmed the presence of a group of intraepithelial lesions (MIN) with not only overlapping morphologic features, but also immunoprofiles distinctly different from either DIN or LIN. These MIN lesions may reflect either a transient stage in the development of DIN and LIN (the immediate post-stem cell stage) or a plastic group in transition from one type to the other. This group needs further evaluation for better understanding of its significance, pattern of progression, and behavior.

Beyond tamoxifen new endpoints for breast cancer chemoprevention, new drugs for breast cancer prevention

Although tamoxifen appears to markedly reduce breast cancer risk in women with a prior diagnosis of atypical hyperplasia or in situ carcinoma, it is not clear what other groups of women receive substantial benefit. Major breast chemoprevention priorities are to (1) develop new agents that (a) have fewer side effects, (b) are effective in ER--as well as tamoxifen-resistant precancerous tissue, and (c) are compatible with hormone therapy; and (2) develop efficient clinical strategies including prognostic and predictive morphologic and molecular biomarkers. Breast tissue may be repeatedly sampled for evidence of intraepithelial neoplasia by fine needle aspiration, ductal lavage, or needle biopsy to select candidates at highest short-term risk as well as to monitor response in small proof of principle studies prior to a large cancer incidence trial. Molecular marker expression may also be used to select a cohort most likely to respond to a particular agent. A large number of new agents are attractive as potential prevention agents and some are already in clinical prevention testing. Compounds which should be effective in ER + precancerous tissue but may have a better side-effect profile include new selective estrogen receptor modulators which lack uterine estrogen agonist activity, isoflavones, aromatase inactivators/inhibitors for postmenopausal women, and gonadotropin-releasing hormone regimens for premenopausal women. Retinoids, rexinoids, and deltanoids may be efficacious in ER+ tissue resistant to tamoxifen. Agents which should theoretically have activity in ER- or ER+ precancerous tissue include polyamine synthesis inhibitors, tyrosine kinase inhibitors, combined demethylating agents and histone deacetylase inhibitors, as well as metalloprotease and angiogenesis inhibitors. Sample Phase I and Phase II clinical trial designs are reviewed using modulation of molecular markers and breast intraepithelial neoplasia as the major endpoints.

Breast cancer chemoprevention: beyond tamoxifen

A large number of new potential chemoprevention agents are available that target molecular abnormalities found in estrogen receptor (ER)-negative and/or ER-positive precancerous breast tissue and have side effect profiles that differ from tamoxifen. Classes of agents currently undergoing evaluation in clinical prevention trials or those for which testing is planned in the near future include new selective ER modulators, aromatase inactivators/inhibitors, gonadotrophin-releasing hormone agonists, monoterpenes, isoflavones, retinoids, rexinoids, vitamin D derivatives, and inhibitors of tyrosine kinase, cyclooxygenase-2, and polyamine synthesis. New clinical testing models will use morphological and molecular biomarkers to select candidates at highest short-term risk, to predict the response to a particular class of agent, and to assess the response in phase II prevention trials. If validated, morphological and molecular markers could eventually replace cancer incidence as an indicator of efficacy in future phase III trials.

The mammary pathology of genetically engineered mice: the consensus report and recommendations from the Annapolis meeting

NIH sponsored a meeting of medical and veterinary pathologists with mammary gland expertise in Annapolis in March 1999. Rapid development of mouse mammary models has accentuated the need for definitions of the mammary lesions in genetically engineered mice (GEM) and to assess their usefulness as models of human breast disease. The panel of nine pathologists independently reviewed material representing over 90% of the published systems. The GEM tumors were found to have: (1) phenotypes similar to those of non-GEM; (2) signature phenotypes specific to the transgene; and (3) some morphological similarities to the human disease. The current mouse mammary and human breast tumor classifications describe the majority of GEM lesions but unique morphologic lesions are found in many GEM. Since little information is available on the natural history of GEM lesions, a simple morphologic nomenclature is proposed that allows direct comparisons between models. Future progress requires rigorous application of guidelines covering pathologic examination of the mammary gland and the whole animal. Since the phenotype of the lesions is an essential component of their molecular pathology, funding agencies should adopt policies ensuring careful morphological evaluation of any funded research involving animal models. A pathologist should be part of each research team.

Is centralized histopathology review necessary for screen-detected breast lesions?

To address quality requirements for breast pathology in the Australian screening programme, one breast cancer Screening and Assessment Service initiated a process of central pathologic review of all lesions detected through the service. The aim of this study was to measure concordance between the initial and review pathology, and to assess the merit of routine review. Concordance was measured by observed agreement and the kappa statistic for 267 women with 273 lesions. Concordance was excellent for the four classification schemes examined, good for the identification of benign lesions and hyperplasia, and excellent for the identification of DCIS or invasive carcinoma. For the sub-categorization of hyperplasias and invasive carcinomas concordance was good, but was poor for the sub-typing of DCIS. Initial and review concordance was acceptable, suggesting that disagreement among pathologists may not present a major impediment to the provision of dependable diagnoses. Full case review is unnecessary for benign lesions or invasive carcinoma, but should be maintained for DCIS and hyperplasias.

Use of keratin 35betaE12 as an adjunct in the diagnosis of mammary intraepithelial neoplasia-ductal type--benign and malignant intraductal proliferations

A variety of studies have investigated the role of low molecular weight (LMW) and high molecular weight (HMW) cytokeratin (CK) expression in the normal breast and invasive breast carcinomas. A few studies with small numbers of cases have addressed this issue in intraductal proliferations of the breast. This study investigates the expression of these CKs in a large series of ductal intraepithelial neoplasias of the breast. We examined 150 ductal carcinomas in situ (DCIS), 35 cases of intraductal hyperplasia (IDH), and 15 cases of atypical intraductal hyperplasia (AIDH). Immunohistochemistry was performed using monoclonal antibodies against CK-34betaE12 (HMW CK), CK-8, and CK-19 (LMW CK) on formalin-fixed, paraffin-embedded tissue. The intensity (0, +1, +2, +3) and percentage of positive intraductal cells (0-100%) were multiplied to obtain a score from 0 to 300. The immunoprofiles of IDH, AIDH, and DCIS were categorized into four groups showing negative or low (0-60), moderate (61-100), high (101-200), and very high (201-300) scores. All cases of IDH showed an intensely positive reaction (high to very high scores) for CK-34betaE12. In contrast, 90% of the DCIS showed a negative or only focal and weak reaction (negative or low score) for this antigen. The remaining 10% of DCIS showed a positive immunoreaction for CK-34betaE12 with moderate to high scores. All cases of florid IDH and 96% of cases of DCIS expressed CK-8 intensely with high to very high scores. Although CK-19 was strongly expressed in 97% of cases of IDH (high to very high scores), a very high score was also found in 80% of cases of DCIS that were positive for CK-19. Of the 15 AIDHs, 80% had a negative or only focal reaction (negative or low score) for CK-34betaE12 and the remaining 20% had a moderate to high score for this antigen. Although CK-8 was strongly positive in 87% of cases of AIDH (high to very high scores), only 53.5% of AIDHs showed intense positivity for CK-19. The present study clearly shows that the immunoprofile of IDH is different from DCIS as far as HMW CK is concerned. Although florid IDH is characterized by a diffuse and intense immunoreaction for HMW CK, the lack of or only weak positivity for HMW CK (CK-34betaE12) is, in most cases, a hallmark of ductal carcinoma in situ. The immunoprofile of AIDH is very similar to that of DCIS. The expression of CK-8 and CK-19 is not useful in separating the various categories of ductal intraepithelial proliferations of the breast. We recommend the use of CK-34betaE12 as an adjunct in the diagnosis of a variety of problematic intraductal proliferations of the breast.

Premalignant breast lesions: role for biological markers in predicting progression to cancer

Biological markers associated with in situ carcinoma and atypical intraductal hyperplasia in the breast are examined to help in identifying a subgroup of premalignant lesions whose natural history may be influenced by epigenetic factors. The biomarkers may be used as indices in clinical trials aiming to assess the effect of weight reduction, dietary intervention or hormone replacement therapy on the risk of progression to invasive breast cancer. In the current state of knowledge, the expression of oestrogen receptors, p53, bcl-2 and HER-2 neu oncogenes and the Ki-67 index of proliferative activity, are the most useful biomarkers for this purpose. In situ carcinoma of the breast manifests a variety of morphological phenotypes with specific biological characteristics. There is evidence that only a proportion of premalignant lesions are committed to progression to invasive cancer while other lesions undergo spontaneous regression at the time of the menopause. Cross-cultural studies suggest that it is the late-stage epigenetic promoting factors which are responsible for the high incidence of postmenopausal breast cancer in Western women. Obesity in middle life and the Western diet favour the development of hyperinsulinaemic insulin resistance, and the metabolic-endocrine effects of its concomitants may promote mammary carcinogenesis around the time of the menopause and increase the incidence of invasive cancer after the menopause. Because biomarker changes in premalignant lesions are nearer in time to these promoting influences, they could provide intermediate endpoints for testing the hypothesis.

Perimenopausal weight gain and progression of breast cancer precursors

This review examines evidence that weight gain in the years leading up to the menopause can contribute to a woman's risk of postmenopausal breast cancer and may involve perimenopausal stimulation of growth in cancer precursor lesions. We used the Medline database since 1980 to examine studies that assessed the association between increased risk of postmenopausal breast cancer and perimenopausal weight gain or abdominal fat accumulation. This review examines possible mechanisms by which the endocrine-metabolic concomitants of hyperinsulinemia may act as late-stage promoters of mammary carcinogenesis. It was found that, in obese postmenopausal women with breast cancer, excess weight is likely to have been gained before menopause. In Western women, evidence of abdominal obesity associated with hyperinsulinemia increases progressively after the age of 40. Weight gain in the years leading up to the menopause mainly involves abdominal obesity which is associated with insulin resistance, increased free estrogen levels, and imbalance in sex steroids levels. These endocrine-metabolic changes are likely to inhibit the tendency for cancer precursor lesions to regress at the menopause and may lead to late-stage promotion of mammary carcinogenesis.

Models for early chemoprevention trials in breast cancer

Several models are being explored for use in the phase I and phase II evaluation of breast cancer chemoprevention agents. The short-term DCIS/small invasive cancer model is probably best used in late phase I trials in conjunction with agents likely to have activity in the progression phase of neoplastic development in addition to activity in earlier phases. The core biopsy or FNA hyperplasia models may be best used with drugs that are likely to have activity primarily in the promotion phase of neoplastic development and that are suitable for longer duration trials lasting several months to years. Morphology currently is the key surrogate endpoint biomarker for assessing efficacy in phase II trials. Other biomarkers that may undergo modulation will have to be validated, in that modulation will have to be shown to be directly related to decreased cancer risk in subsequent phase III trials. Only then can they be considered as validated surrogate endpoint biomarkers and used as stand-alone efficacy markers in phase II trials. Despite accrual challenges and technologic hurdles, interest in phase I and phase II chemoprevention trials is high.