Imaging Characteristics of and Multidisciplinary Management Considerations for Atypical Ductal Hyperplasia and Flat Epithelial Atypia: Review of Current Literature

High-risk lesions of the breast are frequently encountered in percutaneous biopsy specimens. While benign, these lesions have historically undergone surgical excision due to their potential to be upgraded to malignancy. However, there is emerging evidence that a tailored management approach should be considered to reduce overtreatment of these lesions. Flat epithelial atypia (FEA) and atypical ductal hyperplasia (ADH) are two of the most commonly encountered high-risk lesions. FEA has been shown to have a relatively low rate of progression to malignancy, and some guidelines are now recommending observation over routine excision in select cases. Selective observation may be reasonable in cases where the target lesion is small and completely removed at biopsy and when there are no underlying risk factors, such as a history of breast cancer or genetic mutation or concurrent ADH. ADH has the highest potential upgrade rate to malignancy of all the high-risk lesions. Most society guidelines continue to recommend surgical excision of this lesion. More recently, some literature suggests that ADH lesions that appear completely removed at biopsy, involve limited foci (less than two or three) with no necrosis or significant atypia, manifest as a small group of mammographic calcifications, or demonstrate no enhancement at MRI may be reasonable for observation. Ultimately, management of all high-risk lesions must be based on a multidisciplinary approach that considers all patient, radiologic, clinical, and histopathologic factors. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

[Non-genetic indications for risk reducing mastectomies: Guidelines of the National College of French Gynecologists and Obstetricians (CNGOF)]

OBJECTIVE

To determine the value of performing a risk-reducting mastectomy (RRM) in the absence of a deleterious variant of a breast cancer susceptibility gene, in 4 clinical situations at risk of breast cancer.

DESIGN

The CNGOF Commission of Senology, composed of 26 experts, developed these recommendations. A policy of declaration and monitoring of links of interest was applied throughout the process of making the recommendations. Similarly, the development of these recommendations did not benefit from any funding from a company marketing a health product. The Commission of Senology adhered to the AGREE II (Advancing guideline development, reporting and evaluation in healthcare) criteria and followed the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method to assess the quality of the evidence on which the recommendations were based. The potential drawbacks of making recommendations in the presence of poor quality or insufficient evidence were highlighted.

METHODS

The Commission of Senology considered 8 questions on 4 topics, focusing on histological, familial (no identified genetic abnormality), radiological (of unrecognized cancer), and radiation (history of Hodgkin's disease) risk. For each situation, it was determined whether performing RRM compared with surveillance would decrease the risk of developing breast cancer and/or increase survival.

RESULTS

The Commission of Senology synthesis and application of the GRADE method resulted in 11 recommendations, 6 with a high level of evidence (GRADE 1±) and 5 with a low level of evidence (GRADE 2±).

CONCLUSION

There was significant agreement among the Commission of Senology members on recommendations to improve practice for performing or not performing RRM in the clinical setting.

Pitfalls and controversies in pathology impacting breast cancer management

Introduction: Breast cancer is a heterogeneous disease, at morphological, molecular, and clinical levels and this has significant implications for the diagnosis and management of the disease. The introduction of breast screening, and the use of small tissue sampling for diagnosis, the recognition of new morphological and molecular subtypes, and the increasing use of neoadjuvant therapies have created challenges in pathological diagnosis and classification.Areas covered: Areas of potential difficulty include columnar cell lesions, particularly flat epithelial atypia, atypical ductal hyperplasia, lobular neoplasia and its variants, and a range of papillary lesions. Fibroepithelial, sclerosing, mucinous, and apocrine lesions are also considered. Established and newer prognostic and predictive markers, such as immune infiltrates, PD-1 and PD-L1 and gene expression assays are evaluated. The unique challenges of pathology assessment post-neoadjuvant systemic therapy are also explored.Expert opinion: Controversies in clinical management arise due to incomplete and sometimes conflicting data on clinicopathological associations, prognosis, and outcome. The review will address some of these challenges.

Columnar cell lesions of the breast: a practical review for the pathologist

Background

Columnar cell lesions (CCLs) of the breast are characterized by the substitution of regular layer of cuboid epithelial by columnar cells covering the terminal duct lobular units (TDLUs). It also comprises a spectrum of lesions characterized by enlarged TDLUs with variably dilated acini lined by columnar epithelial cells, ranging from one or two layers of benign epithelium to stratified epithelium with atypia. With the increasing use of mammography screening scans in the last 30 years, columnar cell lesions (CCLs) have been diagnosed more frequently, often associated with microcalcifications and abnormal calcifications, requiring breast biopsies. This literature review presents the historical development of this entity description, with many terminologies, the CCLs categories, differential diagnoses, immunohistochemical profile and genetic alterations, reproducibility and clinical implications. In addition it discusses the significance of flat epithelial atypia (FEA), a CCL with low-grade cytological atypia.

Practical considerations

FEA are a frequent finding in breast biopsies and should be a warning sign for other possible entities within the lesion area. Since CCLs are an increasingly recognized entity in the diagnostic spectrum of breast proliferative lesions, proper training or tutorials are advisable for general pathologists in order to teach them how to identify CCLs with confidence. Intraductal proliferations with architectural complexities such as cribriform patterns, rigid cellular bridges, and true micropapillary pattern should not fall into the FEA category and are best classified as atypical ductal hyperplasia (ADH) or ductal carcinoma in situ (DCIS).

Conclusions

Among CCLs, FEA actually receives more attention due to atypia involved. FEA has been considered a non-obligate pre-neoplastic lesion and progression of these lesions to invasive cancer has been reported as increasingly low (2–7%). Therefore, controversy to the management of those lesions still remains and further intervention is restricted to cases with other premalignant lesions (ADH, DCIS) or in radiologic-pathologic disagreement.

Isolated Flat Epithelial Atypia on Core Biopsy Specimens Is Associated With a Low Risk of Upgrade at Excision

OBJECTIVES

We present a retrospective review of 111 breast core biopsy specimens with flat epithelial atypia (FEA) and corresponding excision to better understand rates of upgrade following this diagnosis.

METHODS

In total, 252 breast core biopsy specimens were identified. Cases were excluded if biopsy slides or excision results were unavailable, for ipsilateral carcinoma or other findings warranting excision, or biopsy performed for indications other than mammographically detected calcifications. Coincident atypical lobular hyperplasia was not excluded. Diagnoses were confirmed by breast pathologists, and mammographic images were reviewed.

RESULTS

Ultimately, 111 biopsy specimens with FEA were included. In subsequent excisions, one (1%) of 111 showed invasive carcinoma, 20 (18%) atypical ductal hyperplasia, 20 (18%) lobular neoplasia, 31 (28%) FEA, and 39 (35%) no atypical findings.

CONCLUSIONS

FEA on core biopsy specimens is associated with a low rate of upgrade to invasive carcinoma. Close follow-up may be a reasonable alternative to excision for isolated FEA on core needle biopsy specimens.

Flat epithelial atypia in directional vacuum-assisted biopsy of breast microcalcifications: surgical excision may not be necessary

The aim of this study was to analyze the clinicopathological features of patients with flat epithelial atypia, diagnosed in directional vacuum-assisted biopsy targeting microcalcifications, to identify upgrade rate to in situ ductal or invasive breast carcinoma, and determine factors predicting carcinoma in the subsequent excision. We retrospectively evaluated the histological, clinical, and mammographic features of 69 cases from 65 women, with directional vacuum-assisted biopsy-diagnosed flat epithelial atypia with or without atypical ductal hyperplasia or atypical lobular hyperplasia, which underwent subsequent surgical excision. The extent and percentage of microcalcifications sampled by directional vacuum-assisted biopsy were evaluated by mammography. All biopsy and surgical excision slides were reviewed. The age of the women ranged from 40 to 85 years (mean 57 years). All patients presented with mammographically detected microcalcifications only, except in one case that had associated architectural distortion. Extent of calcifications ranged from <1 cm (n = 47), 1-3 cm (n = 15) to > 3 cm (n = 6), and no measurement (n = 1). A mean of 11 cores (range 6-25) was obtained from each lesion. Post-biopsy mammogram revealed >90% removal of calcifications in 81% of cases. Pure flat epithelial atypia represented nearly two-thirds of directional vacuum-assisted biopsy specimens (n = 43, 62%), while flat epithelial atypia coexisted with atypical ductal hyperplasia (18 cases, 26%), or atypical lobular hyperplasia (8 cases, 12%). Upon excision, none of the cases were upgraded to in situ ductal or invasive breast cancer. In one case, however, an incidental, tubular carcinoma (4 mm) was found away from biopsy site. Excluding this case, the upgrade rate was 0%. Our study adds to the growing evidence that diagnosis of flat epithelial atypia on directional vacuum-assisted biopsy for microcalcifications as the only imaging finding is not associated with a significant upgrade to carcinoma on excision, and therefore, excision may not be necessary. Additionally, excision may not be necessary for flat epithelial atypia with atypical ductal hyperplasia limited to ≤2 terminal duct-lobular units, if at least 90% of calcifications have been removed on biopsy.

Multicolor immunofluorescence reveals that p63- and/or K5-positive progenitor cells contribute to normal breast epithelium and usual ductal hyperplasia but not to low-grade intraepithelial neoplasia of the breast

We contend that knowledge about the cellular composition of normal breast epithelium is a prerequisite for understanding proliferative breast disease. Against this background, we used multicolor immunofluorescence to study normal breast epithelium and two types of intraepithelial proliferative breast lesion for expression of the p63, basal keratin K5, glandular keratin K8/18, SMA, ER-alpha, and Ki67. We studied eight normal breast epithelium samples, 12 cases of usual ductal hyperplasia, and 33 cases of low-grade intraepithelial neoplasia (9 flat epithelial atypia, 14 low-grade ductal carcinoma in situ and 10 cases of lobular neoplasia). Usual ductal hyperplasia showed striking similarity to normal luminal breast epithelium including p63+ and/or K5+ luminal progenitor cells and the full spectrum of luminal progeny cells. In normal breast epithelium and usual ductal hyperplasia, expression of ER-alpha was associated with lack of expression of the proliferation antigen Ki67. In contrast, we found in both types of low-grade intraepithelial neoplasia robust expression of keratin K8/18 and a positive association between ER-alpha and Ki67 expression. However, these lesions were consistently negative for p63 and/or K5. Our observational study supports the view that usual ductal hyperplasia and low-grade intraepithelial neoplasia are different entities rather than part of a spectrum of the same disease. We propose a new operational model of cell differentiation that may serve to better understand correlations between normal breast epithelium and proliferative breast diseases. From our data we conclude that p63+ and/or K5+ progenitor cells contribute to maintenance of normal epithelium and usual ductal hyperplasia, but not to low-grade intraepithelial neoplasia of the breast.

Does flat epithelial atypia have rounder nuclei than columnar cell change/hyperplasia? A morphometric approach to columnar cell lesions of the breast

Columnar cell lesions of the breast encompass columnar cell change/hyperplasia (CCC/CCH) and flat epithelial atypia (FEA). These have attracted researchers because emerging data suggest that FEA may represent the earliest histologically detectable non-obligate precursor of breast cancer. However, it is occasionally difficult to distinguish FEA from CCC/CCH because of similar histology. Although the nuclei of FEA are frequently described as relatively round compared with those of CCC/CCH, there are few morphometric studies to support this statement. The aim of this study was to provide objective data as to the nuclear shape in columnar cell lesions. As a shape descriptor, we adopted ellipticity that is defined by the formula 2b/2a, where a is the length of the long axis of the ellipse and b is the length of the short axis. Contrary to circularity, ellipticity reflects the overall configuration of an ellipse irrespective of surface irregularity. Our image analysis included generating whole slide images, extracting glandular cell nuclei, measuring nuclear ellipticity, and superimposing graded colors based on execution of results on the captured images. A total of 7917 nuclei extracted from 22 FEA images and 5010 nuclei extracted from 13 CCC/CCH images were analyzed. There was a significant difference in nuclear roundness between FEA and CCC/CCH with mean ellipticity values of 0.723 and 0.679, respectively (p < 0.001, Welch's t test). Furthermore, FEA with malignancy had significantly rounder nuclei than FEA without malignancy (p < 0.001). Our preliminary results suggest that nuclear ellipticity is a key parameter in reproducibly classifying columnar cell lesions of the breast.

Role of cytology in fibroadenoma with clinging carcinoma

Fibroadenoma is the most common benign breast tumor in adolescent girls and young women with a peak incidence in the second and third decades of life. Carcinoma arising within a fibroadenoma is rare and is usually discovered incidentally. We describe a case of clinging type of ductal carcinoma in situ (DCIS) arising within a fibroadenoma. Clinging carcinoma, a variant of DCIS is an under recognized entity. Diagnosis of DCIS is made based on architecture and cytology. This case report highlights the role of fine needle aspiration cytology in the diagnosis of this entity coexisting in a fibroadenoma.

Morphological parameters of flat epithelial atypia (FEA) in stereotactic vacuum-assisted needle core biopsies do not predict the presence of malignancy on subsequent surgical excision

Flat epithelial atypia (FEA) may represent the earliest precursor of low-grade breast cancer and often coexists with more advanced atypical proliferative breast lesions such as atypical ductal hyperplasia (ADH) and lobular intraepithelial neoplasia (LIN). The present study aims to investigate the association between morphological parameters of FEA and presence of malignancy at surgical excision (SE) and the clinical significance of the association of FEA with ADH and/or LIN. This study included 589 cases of stereotactic 11-gauge vacuum-assisted needle core biopsy (VANCB), reporting a diagnosis of FEA, ADH or LIN with subsequent SE from 14 pathology departments in Italy. Available slides were reviewed, with 114 (19.4 %) showing a malignant outcome at SE. Among the 190 cases of pure FEA, no statistically significant association emerged between clinical-pathological parameters of FEA and risk of malignancy. Logistic regression analyses showed an increased risk of malignancy according to the extension of ADH among the 275 cases of FEA associated with ADH (p = 0.004) and among the 34 cases of FEA associated with ADH and LIN (p = 0.02). In the whole series, a statistically significant increased malignancy risk emerged according to mammographic R1-R3/R4-R5 categories (OR = 1.56; p = 0.04), extension (OR = 1.24; p = 0.04) and grade (OR = 1.94; p = 0.004) of cytological atypia of FEA. The presence of ADH was associated with an increased malignancy risk (OR = 2.85; p < 0.0001). Our data confirm the frequent association of FEA with ADH and/or LIN. A diagnosis of pure FEA on VANCB carries a 9.5 % risk of concurrent malignancy and thus warrants follow-up excision because none of the clinical-pathological parameters predicts which cases will present carcinoma on SE.

Phosphatidylinositol-3-kinase pathway mutations are common in breast columnar cell lesions

The phosphatidylinositol-3-kinase pathway is one of the most commonly mutated pathways in invasive breast carcinoma, with PIK3CA mutations in ∼25% of invasive carcinomas, and AKT1 mutations in up to 5%. Ductal carcinoma in situ, and benign papillomas harbor similar mutations. However, activating point mutations in breast columnar cell lesions have been infrequently studied. Twenty-three breast resection specimens containing columnar cell lesions were identified; 14 with associated invasive carcinoma or carcinoma in situ. DNA extracts were prepared from formalin-fixed paraffin-embedded tissue and screened for a panel of point mutations (321 mutations in 30 genes) using a multiplex PCR panel with mass-spectroscopy readout. PIK3CA mutations were identified in 13/24 columnar cell lesions (54%) and 3/8 invasive carcinomas (37%). The mutation status of columnar cell lesions and associated carcinoma was frequently discordant. Of the 14 cases, only 5 demonstrated the same genotype in matched samples of columnar cell lesions and carcinoma (4 wild type, 1 PIK3CA H1047R). Interestingly, five patients had mutations in columnar cell lesions with wild-type carcinoma; two patients had different point mutations in columnar cell lesions and carcinoma. Only three cases had wild-type columnar cell lesion and mutated carcinoma. The 50% PIK3CA mutation prevalence in columnar cell lesions is greater than reported in most studies of invasive breast cancer. Further, columnar cell lesions and carcinoma were frequently discordant for PIK3CA/AKT1 mutation status. These findings raise interesting questions about the role of PIK3CA/AKT pathway in breast carcinogenesis, and the biologic/precursor potential of columnar cell lesions.

Application of the British National Health Service Breast Cancer Screening Programme classification in 226 breast core needle biopsies: correlation with resected specimens

A retrospective study correlating the diagnosis made on core needle breast biopsy (CNB) with the diagnosis made on the final surgical specimen was done using the British National Health Service Breast Cancer Screening Programme (NHSBSP) classification for CNB on 226 patients during a period of 15 months. Statistical analysis was used to evaluate sensitivity, specificity, and positive and negative predictive values of the NHSBSP diagnostic categories. Cohen κ was used to evaluate the agreement between the diagnosis on CNB and the final pathologic diagnosis in "clinically positive cases." Finally, a comparative analysis between the CNB method and fine needle aspiration biopsy was made. The distribution of our cases for each diagnostic category reflects the literature guidelines, with minor differences in the B2 and B4 groups. Statistical data about the patients' follow-up revealed a small number of false-negative cases in the B1 and B2 categories and no false-positive cases in the B4 and B5 groups. Uncertain malignant lesions (B3 category) were divided into 3 major areas (papillary lesions, fibroepithelial proliferations with cellular stroma, and intraepithelial atypical lesions such as ductal intraepithelial neoplasia grade 1/lobular intraepithelial neoplasia grade 1). Of the 29 patients in the B3 category, 26 underwent surgery. Cohen κ analysis showed a strong statistical correlation (κ = 0.77; Z = 4.3; significance >1.96; α = .05) between CNB diagnosis and surgical pathology final results in the subgroup of high-risk patients (diagnosis, ≥ductal intraepithelial neoplasia grade 1 on CNB). Global diagnostic power of CNB in all 226 cases revealed high sensitivity (88.3%) and slightly lower specificity (72.8%). In 42 "doubtful" cases, synchronous fine needle aspiration biopsy and CNB were performed, showing a complementary role in the diagnostic phase of breast lesions. Core needle breast biopsy represents the criterion standard method in the diagnostic phase of many breast tumors; the NHSBSP classification is a useful reporting system that provides a good standardization of the pathologic diagnosis and provides a clear guideline for the correct management of the patient.

All atypia diagnosed at stereotactic vacuum-assisted breast biopsy do not need surgical excision

The necessity of excision is debatable when atypia are diagnosed at stereotactic vacuum-assisted breast biopsy (microbiopsy). Among the 287 surgical excisions performed at Institut Bergonié from 1999 to 2009, we selected a case-control study group of 151 excisions; 52 involving all the diagnosed cancers and 99 randomly selected among the 235 excisions without cancer, following atypical microbiopsy (24 flat epithelial atypia; 50 atypical ductal hyperplasia; 14 lobular neoplasia; 63 mixed lesions). Mammographical calcification (type, extension, complete removal) and histological criteria of epithelial atypia (type, number of foci, size/extension), topography and microcalcification extension at microbiopsy were compared according to the presence or absence of cancer at excision. Factors associated with cancer at excision were Breast Imaging Reporting and Data System (BI-RADS5) lesions, large and/or multiple foci of mammographical calcifications, histological type, number, size and extension of atypical foci. Flat epithelial atypia alone was never associated with cancer at excision. BI-RADS5, atypical ductal hyperplasia (alone or predominant) and >3 foci of atypia were identified as independent pejorative factors. There was never any cancer at excision when these pejorative factors were absent (n=31). Presence of one (n=59), two (n=23) or three (n=14) factors was associated with cancer in 24, 15 and 13 cases with an odds ratio=5.8 (95% CI: 3-11.2) for each additional factor. We recommend that mammographical data and histological characteristics be taken into account in the decision-making process after diagnosis of atypia on microbiopsy. With experienced senologists and strict histological criteria, some patients could be spared surgery resulting in significant patient, financial and time advantages.