Upgrade rate of percutaneously diagnosed pure flat epithelial atypia: systematic review and meta-analysis of 1,924 lesions

European guidelines for the diagnosis, treatment and follow-up of breast lesions with uncertain malignant potential (B3 lesions) developed jointly by EUSOMA, EUSOBI, ESP (BWG) and ESSO

INTRODUCTION

Breast lesions of uncertain malignant potential (B3) include atypical ductal and lobular hyperplasias, lobular carcinoma in situ, flat epithelial atypia, papillary lesions, radial scars and fibroepithelial lesions as well as other rare miscellaneous lesions. They are challenging to categorise histologically, requiring specialist training and multidisciplinary input. They may coexist with in situ or invasive breast cancer (BC) and increase the risk of subsequent BC development. Management should focus on adequate classification and management whilst avoiding overtreatment. The aim of these guidelines is to provide updated information regarding the diagnosis and management of B3 lesions, according to updated literature review evidence.

METHODS

These guidelines provide practical recommendations which can be applied in clinical practice which include recommendation grade and level of evidence. All sections were written according to an updated literature review and discussed at a consensus meeting. Critical appraisal by the expert writing committee adhered to the 23 items in the international Appraisal of Guidelines, Research and Evaluation (AGREE) tool.

RESULTS

Recommendations for further management after core-needle biopsy (CNB) or vacuum-assisted biopsy (VAB) diagnosis of a B3 lesion reported in this guideline, vary depending on the presence of atypia, size of lesion, sampling size, and patient preferences. After CNB or VAB, the option of vacuum-assisted excision or surgical excision should be evaluated by a multidisciplinary team and shared decision-making with the patient is crucial for personalizing further treatment. De-escalation of surgical intervention for B3 breast lesions is ongoing, and the inclusion of vacuum-assisted excision (VAE) will decrease the need for surgical intervention in further approaches. Communication with patients may be different according to histological diagnosis, presence or absence of atypia, or risk of upgrade due to discordant imaging. Written information resources to help patients understand these issues alongside with verbal communication is recommended. Lifestyle interventions have a significant impact on BC incidence so lifestyle interventions need to be suggested to women at increased BC risk as a result of a diagnosis of a B3 lesion.

CONCLUSIONS

These guidelines provide a state-of-the-art overview of the diagnosis, management and prognosis of B3 lesions in modern multidisciplinary breast practice.

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.

Isolated Flat Epithelial Atypia: Upgrade Outcomes After Multidisciplinary Review-Based Management Using Excision or Imaging Surveillance

Objective

To compare flat epithelial atypia (FEA) upgrade rates after excision versus surveillance and to identify variables associated with upgrade.

Methods

This single-institution retrospective study identified isolated FEA cases determined by percutaneous biopsy from April 2005 through July 2022 with excision or ≥2 years surveillance. All cases were recommended for excision or surveillance based on multidisciplinary discussion of clinical, imaging, and pathologic variables with emphasis on sampling adequacy and significant atypia. Truth was determined by pathology at excision or the absence of cancer on surveillance. Upgrade was defined as cancer occurring ≤2 cm from the biopsy site. Demographic, imaging, and biopsy variables were compared between those that did and did not upgrade.

Results

Among 112 cases of isolated FEA, imaging findings included calcifications in 81.3% (91/112), MRI lesions in 11.6% (13/112), and distortions or masses in 7.1% (8/112). Excision was recommended in 12.5% (14/112) and surveillance in 87.5% (98/112) of cases. Among those recommended for excision, 28.6% (4/14) of cases were upgraded, all to ductal carcinoma in situ. In those recommended for surveillance, 1.0% (1/98) were upgraded to invasive cancer. Overall, FEA had a 4.5% (5/112) upgrade rate, and 2.7% (3/112) also developed cancer >2 cm from the FEA. There were no significant differences in demographic, imaging, and biopsy variables between those that did and did not upgrade to cancer.

Conclusion

Multidisciplinary management of isolated FEA distinguishes those at higher risk of upgrade to cancer (28.6%) in whom surgery is warranted from those at low risk of upgrade (1.0%) who can be managed non-operatively.

Third International Consensus Conference on lesions of uncertain malignant potential in the breast (B3 lesions)

The heterogeneous group of B3 lesions in the breast harbors lesions with different malignant potential and progression risk. As several studies about B3 lesions have been published since the last Consensus in 2018, the 3rd International Consensus Conference discussed the six most relevant B3 lesions (atypical ductal hyperplasia (ADH), flat epithelial atypia (FEA), classical lobular neoplasia (LN), radial scar (RS), papillary lesions (PL) without atypia, and phyllodes tumors (PT)) and made recommendations for diagnostic and therapeutic approaches. Following a presentation of current data of each B3 lesion, the international and interdisciplinary panel of 33 specialists and key opinion leaders voted on the recommendations for further management after core-needle biopsy (CNB) and vacuum-assisted biopsy (VAB). In case of B3 lesion diagnosis on CNB, OE was recommended in ADH and PT, whereas in the other B3 lesions, vacuum-assisted excision was considered an equivalent alternative to OE. In ADH, most panelists (76%) recommended an open excision (OE) after diagnosis on VAB, whereas observation after a complete VAB-removal on imaging was accepted by 34%. In LN, the majority of the panel (90%) preferred observation following complete VAB-removal. Results were similar in RS (82%), PL (100%), and FEA (100%). In benign PT, a slim majority (55%) also recommended an observation after a complete VAB-removal. VAB with subsequent active surveillance can replace an open surgical intervention for most B3 lesions (RS, FEA, PL, PT, and LN). Compared to previous recommendations, there is an increasing trend to a de-escalating strategy in classical LN. Due to the higher risk of upgrade into malignancy, OE remains the preferred approach after the diagnosis of ADH.

Dimorphic cells: a common feature throughout the low nuclear grade breast neoplasia spectrum

Columnar cell lesions (CCLs) are recognized precursor lesions of the low nuclear grade breast neoplasia family. CCLs are cystic enlarged terminal duct lobular units with monotonous (monoclonal) columnar-type luminal cells. CCLs without atypia are regarded as benign and CCLs with atypia as true precursor lesions with clonal molecular changes, a certain progression risk, and an association with more advanced lesions. However, reproducibility of designating atypia in CCL is not optimal, and no objective markers of atypia have been identified, although 16q loss seems to be associated with atypical CCLs. Dimorphic ("pale") cell populations have been described in low nuclear grade ductal carcinoma in situ (DCIS) but not in CCLs and atypical ductal hyperplasia (ADH). Therefore, we searched for pale cells in CCL (N = 60), ADH (N = 41), and DCIS grade 1 (N = 84). Diagnostic criteria were derived from the WHO, and atypia was designated according to the Schnitt criteria. Pale cells occurred in 0% (0/30), 73% (22/30), 56% (23/41), and 76% (64/84) of CCLs without atypia, CCLs with atypia, ADH, and DCIS grade 1, respectively. Pale cells expressed ERα, E-cadherin and p120 and variably cyclin D1, and lacked expression of CK5 and p63. In conclusion, dimorphic "pale" cells occur throughout the low nuclear grade progression spectrum, increasing in frequency with progression. Interestingly, CCL lesions without atypia do not seem to bear showed pale cells, indicating that the presence of pale cells may serve as a diagnostic morphological feature of atypia in CCLs.

[B3 lesions of the breast: histological, clinical, and epidemiological aspects : Update]

B3 lesions of the breast are a heterogeneous group of lesions with uncertain malignant potential encompassing a broad spectrum of histologically distinct alterations that often pose challenging decisions if diagnosed on the preoperative core or vacuum biopsies. B3 lesions are mostly detected due to mammographic calcifications or mass lesions and, in most cases, encompass a spectrum of atypical lesions such as atypical ductal hyperplasia, classic lobular neoplasia, flat epithelial atypia, papillomas, fibroepithelial tumors, and rarely other lesions such as mucocele-like lesions, atypical apocrine lesions, and rare stromal proliferations. The use of immunohistochemical stains (estrogen receptors, basal cytokeratin, myoepithelial markers, and stromal marker panel) is useful in the differentiation of these lesions and allowing proper classification. Regarding clinical management of B3 lesions, the radiological-pathological correlation of the given entity plays the most important key element for the proper next diagnostic and therapeutic step.

Are Columnar Cell Lesions the Earliest Non-Obligate Precursor in the Low-Grade Breast Neoplasia Pathway?

Columnar cell lesions (CCLs) of the breast comprise a spectrum of morphologic alterations of the terminal duct lobular unit involving variably dilated and enlarged acini lined by columnar epithelial cells. The World Health Organization currently classifies CCLs without atypia as columnar cell change (CCC) and columnar cell hyperplasia (CCH), whereas flat epithelial atypia (FEA) is a unifying term encompassing both CCC and CCH with cytologic atypia. CCLs have been increasingly recognized in stereotactic core needle biopsies (CNBs) performed for the assessment of calcifications. CCLs are believed to represent the earliest non-obligate precursor of low-grade invasive breast carcinomas as they share molecular alterations and often coexist with entities in the low-grade breast neoplasia pathway. Despite this association, however, the risk of progression of CCLs to invasive breast carcinoma appears low and may not exceed that of concurrent proliferative lesions. As the reported upgrade rates of pure CCL/FEA when identified as the most advanced high-risk lesion on CNB vary widely, the management of FEA diagnosed on CNB remains controversial. This review will include a historical overview of CCLs and will examine histologic diagnostic criteria, molecular alterations, prognosis and issues related to upgrade rates and clinical management.