Interobserver variability by pathologists in the distinction between cellular fibroadenomas and phyllodes tumors

Margin Width and Local Recurrence in Patients with Phyllodes Tumors of the Breast

BACKGROUND

Optimal surgical margin width for patients with phyllodes tumors (PTs) of the breast remains debated. The aim of this study was to assess the influence of margin width on long-term local recurrence risk.

PATIENTS AND METHODS

This was a single-institution retrospective review of patients with confirmed PT treated from 2008-2015. Margins were defined as positive (ink on tumor), narrow (no tumor at inked margin but < 10mm), or widely free (>/= 10mm). LR rates were estimated by the Kaplan-Meier method.

RESULTS

Among 117 female patients, histology included 55 (47%) benign, 29 (25%) borderline, and 33 (28%) malignant PT. Final margins were positive in 16 (14%), narrow in 32 (27%), widely free in 64 (55%), and unknown in 5 (4%) patients. Compared with margins > 10 mm, patients with positive and narrow margins had a higher LR risk [HR 10.57 (95% CI 2.48-45.02) and HR 5.66 (95% CI 1.19-26.99), respectively]. Among benign PTs, the 10-year LR-free rates were 100%, 94%, and 66% for widely negative, narrow, and positive margins, respectively (p = 0.056). For borderline/malignant PT, the 10-year LR-free rates were 93% and 57% for widely negative and narrow margins, respectively (p = 0.02), with no difference in LR between narrow and positive margin groups (p = 1.00).

CONCLUSIONS

For benign PTs, a margin of no ink on tumor appears sufficient to optimize local control. In patients with borderline or malignant PTs, achieving a wide surgical margin may remain important as narrower margins were associated with LR rates comparable to those with positive margins.

Retrospective analysis of core-needle and vacuum-assisted breast biopsies of B3 fibroepithelial lesions and correlation with results in subsequent surgical specimens

BACKGROUND

Fibroepithelial lesions (FEL) are a heterogeneous group of biphasic tumours that include fibroadenomas (FA) and the rare entity of benign phyllodes tumors (PT) as well as cases where distinction between these two entities is not possible. The histologic distinction between benign PT and cellular FA is still a diagnostic challenge, especially in core-needle biopsy (CNB) or vacuum-assisted biopsy (VAB). Guidelines are not clearly established regarding the management of FEL in CNB or VAB. In this study, we addressed the frequency of B3 FEL diagnosed in CNB or VAB and compared the final histopathological findings in the excision specimens to evaluate up- or downgrading.

METHODS

We identified 117 female patients with the preoperative diagnosis of FEL (B3), PT, or FEL in combination of pure epithelial B3 lesions in CNB or VAB. Clinico-pathological information as well as data on subsequent surgical excision were available for all patients.

RESULTS

PT was diagnosed in 9 (14.8%) and FEL (B3) in 52 (85.2%) cases. Additionally, 56 patients with FA in combination with an additional B3 lesion were identified. Most FEL (B3)/PT initial diagnoses were made in CNB (55.6% of PT; 84.6% of FEL). After the initial biopsy, 7 of 9 (77.8%) patients with initial diagnosis of benign or borderline PT in CNB/VAB and 40 of 52 (77.0%) patients with initial diagnosis of FEL (B3) in CNB/VAB underwent open excision (OE). 4 of 9 cases (44.4%) initially diagnosed as PT were verified, whereas 2 of 9 (22.2%) were downgraded to FA. 20 of 52 cases (38.5%) initially diagnosed as FEL (B3) were downgraded to FA, whereas 11 of 52 cases (21.2%) were diagnosed as benign or borderline PT. One FEL (B3) case was upgraded to malignant PT.

CONCLUSION

Most PT and FEL (B3) diagnoses on CNB/VAB underwent surgical removal. In the final pathological findings of cases classified primarily as FEL (B3), the majority were downgraded to FA, one quarter were upgraded to PT, and a small subset remained as combined FA/PT. In clinical daily practice, we recommend individualized decision-making considering different options (clinical follow-up or removal of the lesion depending on the whole context) in a multidisciplinary preoperative conference.

Phyllodes Tumors of the Breast-Experience in a Tertiary Care Center

Phyllodes tumors (PTs) are rare neoplasms of the breast that are a challenge in clinical practice. Though mostly benign, they are notorious for local recurrence, requiring adjuvant treatments. This study was planned to report the clinicopathological features and outcomes of patients with PT treated at our center. Details of all patients who underwent surgery for PT in the last 6 years (December 2017-December 2023) were obtained from our prospectively maintained database. The demographic, clinical, radiological, pathological, and follow-up details were recorded and analyzed. Statistical analyses were carried out with Jamovi version 2.3.18. Out of 61 suspected PTs by triple assessment, 9 were excluded due to a non-phyllodes diagnosis on histopathology. We included 52 women with a mean age of 38.2 ± 11.0 years, most of whom were premenopausal (57.7%). BI-RADS 4 was the most common finding on radiological assessment (65.4%). Core needle biopsy (CNB) was the most frequently employed modality for histological diagnosis preoperatively (65.4% of cases). Wide local excisions (WLE) and mastectomies were done in 63.5% and 36.5% of patients, respectively. Benign, borderline, and malignant phyllodes constituted 67.3%, 15.4%, and 17.3% of tumors, respectively. Patients undergoing breast conservation surgery (BCS) had a significantly smaller mean tumor diameter than those who underwent a mastectomy (p < 0.001). Overall, the margin positivity rate was 34.6%. Patients undergoing mastectomy developed more local recurrence compared to WLE, although the difference was not significant (p = 0.400). The outcome following surgical excisions of large PTs in terms of margin positivity and local recurrence is the same, irrespective of whether BCS or mastectomy is done. A negative pathological margin width of > 1 mm appears acceptable. Malignant phyllodes with positive margins are associated with a higher rate of recurrence but positive margins in patients with other subtypes may not translate into recurrence, at least in the short term.

Accuracy and Comparison of Core Needle Biopsy Diagnoses With Excision Specimen for Diagnosing Fibroepithelial Lesions of the Breast

Background Core needle biopsy (CNB) for fibroepithelial lesions (FELs) of the breast is commonly encountered by histopathologists. The distinction between fibroadenoma (FA) and phyllodes tumor (PT) can be challenging due to overlapping histological features and the limited nature of CNB material.  Objective This study aimed to assess the accuracy of CNB diagnosis of FA and PT by comparing it with a diagnosis on subsequent surgical excision specimen. Materials and methods A total of 166 cases of FELs of the breast who underwent CNB and subsequent surgical excision between January 2001 and December 2020 were included in our study. All microscopy glass slides were reviewed, and diagnosis confirmed. Results While 125 (75%) cases based on CNB received a definitive diagnosis of either fibroadenoma or PT, the remaining 41 (25%) cases were better classified on excision specimens and were descriptively diagnosed as fibroepithelial lesions on CNB. Diagnoses on CNB and on subsequent excision specimens were concordant in 113 (90.4%) cases. Among 12 cases that were discordant, three cases diagnosed as FA on CNB were upgraded to PT on excision specimens. Nine cases diagnosed as PT on CNB were diagnosed as FA on excision specimens. These included conventional, cellular, juvenile, and complex FA types. Three PTs, which were reported as FA on CNB, measured 6, 12.5, and 17.5 cm in the greatest dimension. Among 23 cases of PT which were further categorized on CNB, tumor categories changed on excision specimens in three cases. The diagnostic accuracy of CNB diagnosis was 90.4%. Conclusion CNB diagnosis showed good accuracy. PT diagnosis should be strongly considered in all tumors measuring >5 cm, especially those exceeding 10 cm. Cellular, juvenile, and complex FAs can be misdiagnosed as PT on CNB. Correlation with clinical and radiological findings can be helpful in establishing correct diagnosis.

Precise diagnosis of breast phyllodes tumors using Raman spectroscopy: Biochemical fingerprint, tumor metabolism and possible mechanism

BACKGROUND

Breast fibroadenomas and phyllodes tumors are both fibroepithelial tumors with comparable histological characteristics. However, rapid and precise differential diagnosis is a tough point in clinical pathology. Given the tendency of phyllodes tumors to recur, the difficulty in differential diagnosis with fibroadenomas leads to the difficulty in optimal management for these patients.

METHOD

In this study, we used Raman spectroscopy to differentiate phyllodes tumors from breast fibroadenomas based on the biochemical and metabolic composition and develop a classification model. The model was validated by 5-fold cross-validation in the training set and tested in an independent test set. The potential metabolic differences between the two types of tumors observed in Raman spectroscopy were confirmed by targeted metabolomic analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

A total of 204 patients with formalin-fixed paraffin-embedded (FFPE) tissue samples, including 100 fibroadenomas and 104 phyllodes tumors were recruited from April 2014 to August 2021. All patients were randomly divided into the training cohort (n = 153) and the test cohort (n = 51). The Raman classification model could differentiate phyllodes tumor versus fibroadenoma with cross-validation accuracy, sensitivity, precision, and area under curve (AUC) of 85.58 % ± 1.77 %, 83.82 % ± 1.01 %, 87.65 % ± 4.22 %, and 93.18 % ± 1.98 %, respectively. When tested in the independent test set, it performed well with the test accuracy, sensitivity, specificity, and AUC of 83.50 %, 86.54 %, 80.39 %, and 90.71 %. Furthermore, the AUC was significantly higher for the Raman model than that for ultrasound (P = 0.0017) and frozen section diagnosis (P < 0.0001). When it came to much more difficult diagnosis between fibroadenoma and benign or small-size phyllodes tumor for pathological examination, the Raman model was capable of differentiating with AUC up to 97.45 % and 95.61 %, respectively. On the other hand, targeted metabolomic analysis, based on fresh-frozen tissue samples, confirmed the differential metabolites (including thymine, dihydrothymine, trans-4-hydroxy-l-proline, etc.) identified from Raman spectra between phyllodes tumor and fibroadenoma.

SIGNIFICANCE AND NOVELTY

In this study, we obtained the molecular information map of breast phyllodes tumors provided by Raman spectroscopy for the first time. We identified a novel Raman fingerprint signature with the potential to precisely characterize and distinguish phyllodes tumors from fibroadenoma as a quick and accurate diagnostic tool. Raman spectroscopy is expected to further guide the precise diagnosis and optimal treatment of breast fibroepithelial tumors in the future.

Management of Benign Phyllodes Tumors: A Dutch Population-Based Retrospective Cohort Between 1989 and 2022

BACKGROUND

Phyllodes tumors (PTs) are rare tumors of the breast. The current National Comprehensive Cancer Network (NCCN) guidelines recommend excision of benign PTs, accepting close or positive margins. Controversy about the optimal treatment for benign PTs remains, especially regarding the preferred margin width after surgical excision and the need for follow-up evaluation.

METHODS

A nationwide retrospective study analyzed the Dutch population from 1989 to 2022. All patients with a diagnosis of benign PT were identified through a search in the Dutch nationwide pathology databank (Palga). Information on age, year of diagnosis, size of the primary tumor, surgical treatment, surgical margin status, and local recurrence was collected.

RESULTS

The study enrolled 1908 patients with benign PT. The median age at diagnosis was 43 years (interquartile range [IQR], 34-52 years), and the median tumor size was 30 mm (IQR, 19-40 mm). Most of the patients (95%) were treated with breast-conserving surgery (BCS). The overall local recurrence rate was 6.2%, and the median time to local recurrence was 31 months (IQR, 15-61 months). Local recurrence was associated with bilaterality of the tumor (odds ratio [OR], 4.91; 95% confidence interval [CI], 2.95-28.30) and positive margin status (OR, 2.51; 95% CI 1.36-4.63). The local recurrence rate was 8.9% for the patients with positive excision margins and 4.0% for the patients with negative excision margins. Notably, for 27 patients (22.6%) who experienced a local recurrence, histologic upgrading of the recurrent tumor was reported, 7 (5.9%) of whom had recurrence as malignant lesions.

CONCLUSIONS

This nationwide series of 1908 patients showed a low local recurrence rate of 6.2% for benign PT, with higher recurrence rates following positive margins.

Comprehensive Clinical-Pathologic Assessment of Malignant Phyllodes Tumors: Proposing Refined Diagnostic Criteria

The latest World Health Organization classification of breast tumors recommends diagnosing malignant phyllodes tumors (MPTs) when all 5 morphologic features are present: permeative borders, marked stromal cellularity, marked stromal cytologic atypia, ≥10 mitoses per 10 high-power fields (HPF), and stromal overgrowth. We assessed the performance of this recommendation to capture MPTs and features predictive of distant metastasis in a multi-institutional retrospective study. Of 65 MPTs, most cases had at least focally permeative borders (58, 89%), with marked stromal cellularity in 40 (61.5%), marked atypia in 38 (58.5%), ≥10 mitoses per 10 HPF in 50 (77%), and stromal overgrowth in 56 (86%). Distant metastases were observed in 20 (31%) patients (median follow-up 24.5 mo, 1 to 204). Only 13 of 65 (20%) cases had all 5 morphologic features, while only 7 of 20 (35%) cases with distant metastases had all 5 features. In univariate analysis, only marked stromal atypia ( P =0.004) and cellularity ( P =0.017) were associated with decreased distant metastasis-free survival. In multivariate Cox regression, the combination of stromal overgrowth, marked stromal cellularity, and atypia (C-index 0.721, 95% CI: 0.578, 0.863) was associated with decreased distant metastasis-free survival. The current World Health Organization recommendation will miss a significant number of MPTs with distant metastases. We propose refined diagnostic criteria for MPTs: (1) stromal overgrowth combined with ≥1 feature(s) (marked cellularity, marked atypia, or ≥10 mitoses per 10 HPF), or (2) in the absence of stromal overgrowth, marked cellularity combined with ≥1 feature(s) (permeative borders, marked atypia, or ≥10 mitoses per 10 HPF).

Versican core protein aids in the diagnosis and grading of breast phyllodes tumor

Phyllodes tumors (PTs) are biphasic fibroepithelial lesions that occur in the breast. Diagnosing and grading PTs remains a challenge in a small proportion of cases, due to the lack of reliable specific biomarkers. We screened a potential marker versican core protein (VCAN) through microproteomics analysis, validated its role for the grading of PTs by immunohistochemistry, and analyzed the correlation between VCAN expression and clinicopathological characteristics. Cytoplasmic immunoreactivity for VCAN was identified in all benign PT samples, among which 40 (93.0 %) showed VCAN-positive staining in ≥50 % of tumor cells. Eight (21.6 %) borderline PT samples showed VCAN-positive staining in ≥50 % of the cells with weak to moderate staining intensity, whereas 29 samples (78.4 %) showed VCAN-positive staining in <50 % of the cells. In malignant PTs, 16 (84.2 %) and three (15.8 %) samples showed VCAN-positive staining in <5 % and 5-25 % of stromal cells, respectively. Fibroadenomas showed a similar expression pattern to benign PTs. Fisher's exact test showed that the percentages of positive cells (P < .001) and staining intensities (P < .001) of tumor cells were significantly different between the five groups. VCAN positivity was associated with tumor categories (P < .0001) and CD34 expression (P < .0001). The expression of VCAN gradually decreases as the tumor categories increases, following recurrence. To the best of our knowledge, our results are the first in the literature to reveal that VCAN is useful for diagnosing and grading PTs. The expression level of VCAN appeared to be negatively associated with PT categories, suggesting that dysregulation of VCAN may be involved in the tumor progression of PTs.

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.

Gene Expression Profiling of Fibroepithelial Lesions of the Breast

Fibroepithelial lesions of the breast (FELs) are a heterogeneous group of neoplasms exhibiting a histologic spectrum ranging from fibroadenomas (FAs) to malignant phyllodes tumors (PTs). Despite published histologic criteria for their classification, it is common for such lesions to exhibit overlapping features, leading to subjective interpretation and interobserver disagreements in histologic diagnosis. Therefore, there is a need for a more objective diagnostic modality to aid in the accurate classification of these lesions and to guide appropriate clinical management. In this study, the expression of 750 tumor-related genes was measured in a cohort of 34 FELs (5 FAs, 9 cellular FAs, 9 benign PTs, 7 borderline PTs, and 4 malignant PTs). Differentially expressed gene analysis, gene set analysis, pathway analysis, and cell type analysis were performed. Genes involved in matrix remodeling and metastasis (e.g., MMP9, SPP1, COL11A1), angiogenesis (VEGFA, ITGAV, NFIL3, FDFR1, CCND2), hypoxia (ENO1, HK1, CYBB, HK2), metabolic stress (e.g., UBE2C, CDKN2A, FBP1), cell proliferation (e.g., CENPF, CCNB1), and the PI3K-Akt pathway (e.g., ITGB3, NRAS) were highly expressed in malignant PTs and less expressed in borderline PTs, benign PTs, cellular FAs, and FAs. The overall gene expression profiles of benign PTs, cellular FAs, and FAs were very similar. Although a slight difference was observed between borderline and benign PTs, a higher degree of difference was observed between borderline and malignant PTs. Additionally, the macrophage cell abundance scores and CCL5 were significantly higher in malignant PTs compared with all other groups. Our results suggest that the gene-expression-profiling-based approach could lead to further stratification of FELs and may provide clinically useful biological and pathophysiological information to improve the existing histologic diagnostic algorithm.

Recurrence is Not Associated with Margin Status in Phyllodes Tumor

BACKGROUND

Phyllodes tumor (PT) is a rare fibroepithelial neoplasm of the breast. The proper extent of resection is still under debate. This study aimed to investigate the optimal surgical margin to prevent recurrence after surgery for PT and to evaluate risk factors for local recurrence (LR).

METHODS

Retrospective analysis of a prospective cohort database was performed. Patients who underwent curative surgery for PT at Seoul National University Bundang Hospital between July 2003 and February 2022 were reviewed.

RESULTS

Of the 439 patients included, 285 were benign, 129 were borderline, and 25 were malignant. There was no statistically significant difference in 5-year disease-free survival (DFS) between margin-negative and margin-involved patients (87.3% vs. 85.1%, p = 0.081). When patients were classified into groups, according to margin status, as conventional (≥ 1 cm from tumor), close (< 1 cm from tumor), or involved, 5-year DFS rates were also similar (100% vs. 86.9% vs. 85.1%, p = 0.170). In subgroup analysis for different histologic grades, 5-year DFS was not affected by margin involvement. In univariate analysis, large tumor size (> 5 cm; hazard ratio [HR] 2.857, p = 0.028) and infiltrative tumor border (HR 3.096, p = 0.012) were independent risk factors for LR. Further multivariate analysis found both factors to be prognostic.

CONCLUSIONS

Recurrence was not significantly influenced by margin status in all histological grades. In benign and borderline tumors, local excision without wide surgical margins could be sufficient, and watchful waiting could be an option for patients with positive margins after initial surgery.

Fibroepithelial Lesion Spectrum: A Case Report Documenting a Possible Transformation to a Malignant Phyllodes Tumor

We discuss the radiological-pathological aspects of a rare case of transformation of a presumed fibroadenoma (FA) to a malignant phyllodes tumor (PT) and review the literature. Phyllodes tumors often show heterogeneous histologic features with some areas indistinguishable on core needle biopsy. A core biopsy is often a small representation of a larger lesion. As such, a complete excisional biopsy is often needed for a definitive pathologic diagnosis. Careful clinical and imaging correlation and follow-up are necessary, even in a benign fibroepithelial lesion (FEL).

Refining the classification of breast phyllodes tumours

Phyllodes tumours of the breast are uncommon fibroepithelial neoplasms that pose recurrent classification challenges, in large part due to the multiple histological parameters of stromal hypercellularity and atypia, stromal mitotic count, stromal overgrowth and tumour borders, that are used for grading. While the World Health Organization (WHO) Classification of Breast Tumours provides recommendations on diagnostic features, defining criteria are not always applied in routine practice. Lack of concordance among pathologists in typing and grading further underscores the classification difficulties, especially in the borderline category. Although there has been significant molecular information on phyllodes tumours in recent years which has been diagnostically helpful, it has not been translated into daily clinical practice. In order to refine the classification of phyllodes tumours into one that is simple yet comprehensive, reproducible and prognostically precise, a multipronged approach is needed that leverages on global contributions of the International Fibroepithelial Consortium, support by the International Collaboration on Cancer Classification and Research (IC³ R) in amalgamating evidence translation, and guidance from the International Collaboration on Cancer Reporting (ICCR) for standardised reporting. It is hoped that the evidence generated can be used towards refining the classification of phyllodes tumours for the future.

Spindle Cell Lesions of the Breast: A Diagnostic Algorithm

CONTEXT.—

Spindle cell lesions of the breast represent a broad spectrum of entities, ranging from nonneoplastic reactive conditions to high-grade malignant tumors. The wide range makes breast spindle cell lesions a diagnostic pitfall.

OBJECTIVE.—

To review the classification of spindle cell lesions of the breast, including clinical features, morphologic characteristics, and the role of immunohistochemistry as well as molecular tools in assisting the differential diagnosis. A diagnostic algorithm will be proposed.

DATA SOURCES.—

Literature and personal experience are the sources for this study.

CONCLUSIONS.—

Spindle cell lesions of the breast can be classified as biphasic or monophasic, with the former including both spindle cell and epithelial components, and the latter including only spindle cell elements. Each category is further subclassified as low or high grade. In the biphasic low-grade group, fibroadenoma and benign phyllodes tumor are the most common lesions. Other uncommon lesions include hamartoma, adenomyoepithelioma, and pseudoangiomatous stromal hyperplasia. In the biphasic high-grade group, borderline/malignant phyllodes tumor and biphasic metaplastic carcinoma are the main lesions to consider. In the monophasic low-grade group, reactive spindle cell nodule, nodular fasciitis, myofibroblastoma, fibromatosis, and fibromatosis-like metaplastic carcinoma have to be considered. In the monophasic high-grade group, the possible lesions are monophasic spindle cell metaplastic carcinoma, primary breast sarcoma, and metastases. Awareness of the clinical history and careful evaluation of any epithelial differentiation (with a large immunohistochemical panel) are crucial in the distinction.

Morphological features of 52 cases of breast phyllodes tumours with local recurrence

Typical phyllodes tumours (PTs) of the breast are fibroepithelial neoplasms characterised histologically by stromal hypercellularity and leaf-like structures. However, morphological changes may be atypical in some cases, increasing the difficulty of diagnosis and the likelihood of misdiagnosis. To provide more morphological clues for pathological diagnosis of PTs, we retrospectively analysed 52 PT cases with typical morphological features after recurrence, and summarized the clinicopathological characteristics of the paired primary tumours. We found five special histological features in the primary tumours distinct from classic PTs, namely (1) PTs with epithelioid feature (three cases); (2) PTs with gland-rich feature (eight cases); (3) PTs with fibroadenoma-like feature (20 cases); (4) PTs with myxoid fibroadenoma-like feature (five cases); and (5) PTs with pseudohemangiomatoid stromal hyperplasia–like feature (four cases). All the features can exist independently, and a few cases displayed more than two distinctive features at the same time. In this cohort of recurrent PTs, all the primary tumours were absent of recognisable stromal hypercellularity and leaf-like structures that are the critical diagnostic criteria of PTs; however, they showed some other non-classic characteristics which may provide significant clues for the diagnosis of PTs. Particularly, tumours with epithelioid feature displayed high grade at earlier stages, tumours with fibroadenoma-like feature were most likely to be confused with classical fibroadenomas, and tumours with myxoid feature were prone to be neglected because of their hypocellularity.

Malignant phyllodes tumor of the breast: a systematic review

Phyllodes tumors (PT) are fibroepithelial neoplasms of the breast showing a peculiar leaf-like appearance. They account for 0.3 to 1% of all primary breast tumors and 2.5% of all fibroepithelial breast tumors. PT are classified into benign, borderline and malignant based upon their stromal morphology with a distribution of 60%, 20%, and 20%, respectively. Malignant PT of the breast constitute an uncommon challenging group of fibroepithelial neoplasms. They have a relatively high tendency to recur, although distant metastasis is uncommon, and nearly exclusive to malignant PT. Adequate surgical resection remains the standard approach to achieve maximal local control. Giant malignant PT are rare and a pose a diagnostic dilemma for pathologists, especially when comprised of sarcomatous elements. This review highlights the morphological features of PT detected in cytology and histology specimens and discusses diagnostic pitfalls and differential diagnosis.

Artificial intelligence modelling in differentiating core biopsies of fibroadenoma from phyllodes tumor

Breast fibroepithelial lesions (FEL) are biphasic tumors which consist of benign fibroadenomas (FAs) and the rarer phyllodes tumors (PTs). FAs and PTs have overlapping features, but have different clinical management, which makes correct core biopsy diagnosis important. This study used whole-slide images (WSIs) of 187 FA and 100 PT core biopsies, to investigate the potential role of artificial intelligence (AI) in FEL diagnosis. A total of 9228 FA patches and 6443 PT patches was generated from WSIs of the training subset, with each patch being 224 × 224 pixel in size. Our model employed a two-stage architecture comprising a convolutional neural network (CNN) component for feature extraction from the patches, and a recurrent neural network (RNN) component for whole-slide classification using activation values from the global average pooling layer in the CNN model. It achieved an overall slide-level accuracy of 87.5%, with accuracies of 80% and 95% for FA and PT slides respectively. This affirms the potential role of AI in diagnostic discrimination between FA and PT on core biopsies which may be further refined for use in routine practice.

An integrative ultrasound-pathology approach to improve preoperative phyllodes tumor classification: A pilot study

OBJECTIVE

Preoperative diagnosis of phyllodes tumor (PT) is challenging, core-needle biopsy (CNB) has a significant rate of understaging, resulting in suboptimal surgical planification. We hypothesized that the association of imaging data to CNB would improve preoperative diagnostic accuracy compared to biopsy alone.

METHODS

In this retrospective pilot study, we included 59 phyllodes tumor with available preoperative imaging, CNB and surgical specimen pathology.

RESULTS

Two ultrasound features: tumor heterogeneity and tumor shape were associated with tumor grade, independently of CNB results. Using a machine learning classifier, the association of ultrasound features with CNB results improved accuracy of preoperative tumor classification up to 84%.

CONCLUSION

An integrative approach of preoperative diagnosis, associating ultrasound features and CNB, improves preoperative diagnosis and could thus optimize surgical planification.

MED12 exon 2 and TERT promoter mutations in primary and recurrent breast fibroepithelial lesions

The genetic alterations in the recurrent breast fibroepithelial tumors are poorly understood. In the present study, we aimed to investigate mediator protein complex subunit 12 (MED12) exon 2 and telomerase reverse transcriptase (TERT) promoter mutations in a series of primary and recurrent fibroepithelial tumors. Sanger sequencing for MED12 exon 2 and TERT promoter was performed in 26 pairs of primary and recurrent fibroepithelial tumors (19 pairs of phyllodes tumors and seven pairs of fibroadenomas). The relationship between the genotypes and clinicopathological variables was also analyzed. MED12 mutation was identified in 19 primary tumors (12 phyllodes tumors and 7 fibroadenomas) and 17 recurrences (14 phyllodes tumors and three fibroadenomas). Most recurrent phyllodes tumors retained the original MED12 variants (17/19). Six recurrent fibroadenomas showed different MED12 variants from their paired primary tumors (6/7). TERT promoter mutation was identified in 13 primary phyllodes tumors (13/19) and 15 recurrent phyllodes tumors (15/19). However, it was only identified in one primary fibroadenoma (1/7). Recurrent phyllodes tumors often retained the original MED12 and TERT promoter mutations, while recurrent fibroadenomas often acquired new MED12 mutations. Our findings suggest that recurrent phyllodes tumors may be "true recurrence," and TERT mutant "benign fibroepithelial tumors" should be treated as phyllodes tumors.

Genetic differences between benign phyllodes tumors and fibroadenomas revealed through targeted next generation sequencing

Breast fibroepithelial lesions are biphasic tumors which comprise the common benign fibroadenomas (FAs) and the rarer phyllodes tumors (PTs). This study analyzed 262 (42%) conventional FAs, 45 (7%) cellular FAs, and 321 (51%) benign PTs contributed by the International Fibroepithelial Consortium, using a previously curated 16 gene panel. Benign PTs were found to possess a higher number of mutations, and higher rates of cancer driver gene alterations than both groups of FAs, in particular MED12, TERT promoter, RARA, FLNA, SETD2, RB1, and EGFR. Cases with MED12 mutations were also more likely to have TERT promoter, RARA, SETD2, and EGFR. There were no significant differences detected between conventional FAs and cellular FAs, except for PIK3CA and MAP3K1. TERT promoter alterations were most optimal in discriminating between FAs and benign PTs. Our study affirms the role of sequencing and key mutations that may assist in refining diagnoses of these lesions.

Correlations of morphological features and surgical management with clinical outcome in a multicentre study of 241 phyllodes tumours of the breast

AIMS

Phyllodes tumours (PTs) represent an unusual but complex group of breast lesions with a tendency to recur locally and, less commonly, metastasise. On core biopsies, their appearances can be difficult to discriminate from those of other fibroepithelial lesions, which may compromise their surgical management. The aims of this study were to assess the preoperative diagnosis of PTs and to evaluate the impacts of surgical management and morphological features on their behaviour.

METHODS AND RESULTS

We combined datasets from three centres over two decades, including core biopsies, excision specimens, and follow-up. Core biopsy results were compared with final excision specimens. The relationships of surgical procedure and morphological features with local recurrence (LR) and metastasis were assessed. Two hundred and forty-one PTs were studied. Core biopsy resulted in a diagnosis of possible or definite PT in 76% of cases. Malignant tumours were more likely to be larger, occurred at an older age, and were surgically more challenging, with difficulties being encountered in achieving negative margins. There were 12 cases (5%) that showed LR alone, and another six cases (2.5%) that had distant metastases. Morphological features associated with adverse outcome were grade of PT, increased mitotic counts, necrosis, infiltrative margins, stromal atypia, and heterologous components. Both LR and metastatic behaviour correlated with larger size and distance to margins.

CONCLUSIONS

Our results suggest that excision margins have a significant impact on LR of PT, whereas metastatic behaviour is influenced by tumour biology. We add to the evidence base on histological features of tumours that contribute to long-term outcomes of PT patients.

Fibroepithelial Lesions (FELs) of the Breast: Is Routine Excision Always Necessary?

BACKGROUND

When needle core biopsies (NCBs) of the breast reveal fibroepithelial lesions (FELs), excision is often performed to rule out a phyllodes tumor (PT), despite low malignancy rates. Consequently, the natural history of observed FELs is not well described. We analyzed the malignancy risk in excised FELs and the natural history of FELs undergoing active surveillance (AS).

METHODS

We retrospectively studied the pathology and imaging records of 215 patients with FELs (n = 252) diagnosed on NCB. Incidence of growth was determined by Kaplan-Meier method.

RESULTS

Of 252 FELs, 80% were immediately excised and 20% underwent AS. Of the excised FELs, 198 (98%) were benign: fibroadenoma (FA) or benign breast tissue in 137 (68%), benign PT in 59 (29%), or LCIS in 2 (1%). Borderline PT or malignant lesions were found in 4 (2%). On ultrasound, malignant and borderline PTs were larger than benign lesions [median 3.9 vs 1.3 cm, p = 0.006]. Fifty FELs underwent AS, with a median follow-up of 17 (range 2-79) months. The majority remained stable or decreased in size: at 2 years, only 35% increased in volume by ≥ 50%. Of those tumors undergoing AS that were later excised (n = 4), all were benign.

CONCLUSIONS

Almost all FELs (98%) were benign on surgical excision, and the majority undergoing AS remained stable, with benign pathology if later excised. Most FELs on NCB can be safely followed with US, with surgery reserved for patients with FELs that are large, symptomatic, or growing. This could spare most women with FELs unnecessary surgery.

Expression of lymphoid enhancer-binding factor 1 in breast fibroepithelial lesions

Phyllodes tumors (PTs) are rare epithelial-mesenchymal tumors of the breast with malignant potential. Here, we evaluate the nuclear expression of lymphoid enhancer-binding factor 1 (LEF-1), a transcription factor downstream of Wnt/β-catenin signaling, in fibroepithelial lesions of the breast. Excised fibroepithelial lesions of the breast were retrospectively reviewed, blinded to the original diagnosis, and classified according to World Health Organization (WHO) criteria. A tissue microarray (TMA) was composed with two representative cores from each case, including 24 benign lesions, 11 borderline phyllodes, and 8 malignant PTs. β-Catenin, LEF-1, p120, and E-cadherin immunohistochemistry was performed on the TMA, and staining was quantified. The malignant/borderline PTs showed higher stromal LEF-1 expression than benign tumors (P < 0.001). Stromal cells expressed LEF-1 in 100% (16/16 of core TMA) of malignant phyllodes, compared with 73% (16/22) borderline and 27% (13/48) benign tumors. The average LEF-1 H-score was 24.9, 6.1, and 1.5 for malignant, borderline, and benign tumors, respectively. Nuclear expression of β-catenin in the stromal component was more often seen in malignant than in borderline and benign tumors (44% versus 32% and 23%, respectively). Nine TMA cores of malignant tumors without nuclear β-catenin staining demonstrated LEF-1 expression. Both LEF-1 and nuclear β-catenin showed expression in the majority of borderline/malignant PTs suggesting a biological progression of Wnt/β-catenin pathway activation in the stromal component from benign to malignant tumors. Inhibitors for the Wnt/β-catenin pathway may provide alternative treatment options in the future for malignant or metastatic PTs.

Fibroadenomas: a multidisciplinary review of the variants

Fibroadenomas are the most common benign breast lesions in women. Hormonal activities, particularly an increase in oestrogenic activity, have an important role in the aetiology of fibroadenomas. They are commonly detected incidentally. Most fibroadenomas have similar imaging findings and these lesions can be defined as simple fibroadenomas (SFAs). However, due to different histopathologic characteristics and components, variants of fibroadenomas have been described. These variants include; juvenile, giant, complex, myxoid, cellular, and hyalinised fibroadenomas. The diagnoses of these variants are important. They have different clinical behaviours, potential for malignant transformation, and treatment strategies. We present imaging findings of SFAs and other variants of fibroadenomas. To our knowledge, there is no review in which imaging findings of all fibroadenoma variants are presented together.

Core needle biopsy diagnosis of fibroepithelial lesions of the breast: a diagnostic challenge

Fibroepithelial lesions (FEL) of the breast are biphasic neoplasms consisting of proliferative epithelial and stromal components and include fibroadenoma, phyllodes tumour and periductal stromal tumour. Core needle biopsy (CNB) is a commonly used diagnostic modality for investigation of breast lesions. As the accurate diagnosis of FEL requires integrated assessment of both epithelial and stromal components, this may create problems in small biopsies with limited sampling. In this review, common problems encountered in CNB of FEL are discussed, including establishing a diagnosis of borderline/malignant phyllodes tumour in a biopsy consisting of malignant spindle cells, differentiating phyllodes tumour from fibroadenoma on CNB, grading of phyllodes tumour of intermediate histological grade and assessment of periductal stromal tumours. The approaches are detailed systematically based on histology, immunohistochemistry and molecular characterisation. This comprehensive approach may aid in dealing with the overlapping histological appearance of FEL and sampling limitations of CNB.

Histopathologic, immunophenotypic, and proteomics characteristics of low-grade phyllodes tumor and fibroadenoma: more similarities than differences

Distinguishing low-grade phyllodes tumor from fibroadenoma is practically challenging due to their overlapping histologic features. However, the final interpretation is essential to surgeons, who base their management on the final pathology report. Patients who receive a diagnosis of fibroadenoma might not undergo any additional intervention while lumpectomy with wide margins is the standard of care for phyllodes tumor, which can have significant cosmetic consequences. We studied the clinical, immunophenotypic, and proteomics profiles of 31 histologically confirmed low-grade phyllodes tumor and 30 fibroadenomas. Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) and immunohistochemistry for Ki-67, p53, β-catenin, and E-cadherin were performed on all cases. After the mass spectra for all 31 cases of low-grade phyllodes tumor and 30 cases of fibroadenoma were collected, an average peak value for all cases was generated. There was no significant difference in the overall mass spectra pattern in any of the peaks identified. There was also overlap in the percentage of cells staining positive for Ki-67, p53, β-catenin, and E-cadherin. The two groups of patients showed no statistically significant difference in age, tumor size, or disease-free survival. Neither group developed malignant transformation, distant metastases, or disease-related mortality. We have demonstrated low-grade phyllodes tumor and fibroadenoma to show significant overlapping clinical and proteomics features.

Periductal Stromal Tumors and Phyllodes Tumors Represent a Spectrum of Fibroepithelial Lesions: What Is in a Name?

Periductal stromal tumors (PSTs) of the breast are considered as a rare subtype of phyllodes tumors. These rare fibroepithelial lesions display a biphasic morphology, characterized by a cellular stroma surrounding benign ducts. Unlike phyllodes tumors, they do not present with a leaflike architecture, rendering a biopsy diagnosis of a PST very challenging. In this report, we compare the histopathological features of a PST with those of a borderline phyllodes tumor. We discuss the differences and similarities between both entities, and we highlight the potential pitfalls of the respective biopsies. Both cases illustrate that PSTs and phyllodes tumors are part of the same spectrum. This biological spectrum implies that "hybrid" lesions do exist, which can be hard to classify.

Genotype-phenotype associations in breast pathology: Achievements of the past quarter century

The first genotype-phenotype relationship in breast pathology developed in 1994 with the discovery of the CDH1 gene. This finding eventually provided biological insight into the characteristic morphology of invasive lobular carcinoma. Subsequent investigative efforts have uncovered additional molecular alterations largely responsible for the histology of several breast neoplasms including secretory carcinoma, adenoid cystic carcinoma, tall cell carcinoma with reversed polarity, fibroepithelial lesions, and most recently, adenomyoepithelioma. Evaluation of the genomic landscape of other special types of breast cancer with distinctive growth patterns, such as invasive mucinous carcinoma, have yet to uncover recurring cytogenetic and/or molecular alterations. Despite the lack of a hallmark alteration in mucinous carcinoma, it is important to note the relative decrease in PIK3CA mutations compared with invasive carcinoma of no special type. In this review, we describe the clinical and pathologic features of breast tumors with recognized genotype-phenotype correlations and summarize the molecular alterations of mucinous carcinoma.

Re-excision or "wait and watch"-a prediction model in breast phyllodes tumors after surgery

Background

The prognosis of breast phyllodes tumors (PTs) largely depending on the pathological grading, which lacks objectivity. This study aimed to develop a nomogram based on clinicopathological features to evaluate the recurrence probability of PTs following surgery.

Methods

Data from 334 patients with breast PTs, who underwent surgical treatment at Sun Yat-sen Memorial Hospital from January 2005 to December 2014, were used to develop a prediction model. Additionally, data of 36 patients from Peking University Shenzhen Hospital (cohort 1) and data of 140 patients from Sun Yat-sen University Cancer Center (cohort 2) during the same period were used to validate the model. The medical records and tumor slides were retrospectively reviewed. The log-rank and Cox regression tests were used to develop a clinical prediction model of breast PTs. All statistical analyses were performed using R and STATA.

Results

Of all 334 patients included in the primary cohort, 224 had benign, 91 had borderline, and 19 had malignant tumors. The 1-, 3-, and 5-year recurrence-free survival was 98.5%, 97.9%, and 96.8%, respectively. Ultrasound-guided vacuum-assisted biopsy (UGVAB) is a non-inferior treatment application in benign PTs compared with open surgery [hazard ratio (HR), 2.38; 95% confidence interval (CI), 0.59–9.58]. Width of surgical margin, mitoses, and tumor border were identified as independent risk factors for breast PTs. A nomogram was developed based on these three variables. The C-index of internal and external validation was 0.71, 0.67 (cohort 1) and 0.73 (cohort 2), respectively.

Conclusions

The study model presented more concise and objective variables to evaluate the recurrence-free survival of patients after surgery, which can help deciding whether to do a re-excision or “wait and watch”.

Accuracy of p53 and ki-67 in the graduation of phyllodes tumor, a model for practical application

Background

The accurate graduation of a phyllodes tumor (PT) is critical for effective treatment as it allows correct surgical management, and avoids inadequate excision for malignant or borderline PT, or surgical overtreatment in benign PT. PTs of the breast are notoriously difficult to classify, and reliable differentiation of a benign PT from a borderline or malignant PT can be problematic, especially among relatively inexperienced pathologists. Although several authors acknowledge a strong relationship between the immunohistochemical expression of p53 and Ki-67 and the histopathological grade of PT—with potential impact on diagnostic accuracy—the literature lacks consensus about which cutoff defines a positive index test. The objective of this study is to establish a practical application score that increases the graduation accuracy of PT through the appropriate use of these auxiliary methods.

Methods

A retrospective study cohort of 146 pathology reviewed PTs surgically removed between January 2000 and December 2015. The Ki-67 test was considered positive if > 10% of neoplastic cells showed nuclear staining. The p53 test was considered positive if > 10% of neoplastic nuclear cells showed nuclear staining in a moderate or strong intensity.

Results

Of the 146 PT cases reviewed, 110 were classified as benign, 16 as borderline, and 20 as malignant. The correlation between age and size with benign, borderline, and malignant subgroups was statistically significant (p < 0.001). Significance was observed in the expression of both Ki-67 and p53 in the comparison of benign, borderline, and malignant PT with p < 0.001 and a 95% confidence interval (CI). When correlating the presence of positivity in either of the two index tests with the diagnosis of borderline or malignant PT, we reached a sensitivity of 100% and a specificity of 91.8 (p < 0.001; 95% CI).

Conclusion

We propose a practical methodology to achieve an accurate grade of PT, based on clearly defined and easy to apply cutoffs of a simple immunohistochemical panel of Ki-67 and p53. A PT positive for either of the index tests should be graded as borderline or malignant, so pathologists can use this test to improve accuracy. We hope this new approach might provide the basis for the development of standardization in using p53 and Ki-67 for grading PT.

Preoperative prediction of margin requirement following a core biopsy result suggestive of a phyllodes tumour

AIM

To determine if imaging features of lesions with a core biopsy suggestive of a phyllodes tumour can be used to identify which lesions require surgical excision with margins.

MATERIALS AND METHODS

Thirty-one lesions were identified from a prospective database of ultrasound visible masses. Demographic, mammographic, and ultrasound features were assessed while blinded to surgical outcome. Features of those lesions requiring a margin and those that did not were compared. Statistical significance was established using the chi-square test and receiver operating characteristic (ROC) curves.

RESULTS

Thirteen lesions (42%) required a margin and 18 lesions (58%) did not. Features found significantly more frequently in those requiring a margin were a poorly defined margin on mammography (7/9 [78%] versus 4/13 [31%]; p=0.04) and at ultrasound, an irregular margin (8/13 [62%] versus 3/18 [17%]; p=0.01), micro-lobulations (7/13 [54%] versus 3/18 [17%]; p=0.028), mixed echogenicity (9/13 [69%] versus 1/18 [6%]; p=0.0002), echogenic clefts (6/13 [46%] versus 1/18 [6%]; p=0.007), posterior enhancement (9/11 [82%] versus 6/18 [33%]; p=0.01), large size (p=0.003) and stiffness at shear-wave elastography (p=0.026). All six screen-detected lesions were benign.

CONCLUSIONS

There are multiple preoperative features that can be used to guide surgical management of lesions with a preoperative core biopsy result suggestive of a phyllodes tumour.

MED12, TERT and RARA in fibroepithelial tumours of the breast

Fibroepithelial tumours are biphasic neoplasms of the breast comprising the common benign fibroadenomas and the less common phyllodes tumours (PTs), which have recurrent potential. PTs are classified into benign, borderline or malignant, based on five histopathological criteria, with malignant PTs having the highest metastatic capability. Accurate diagnosis can be challenging due to the subjective assessment of histopathological parameters. Fibroadenomas bear morphological similarities to benign PTs, while borderline and malignant PTs can sometimes be difficult to distinguish from other spindle cell tumours of the breast. From clonality studies to whole-genome sequencing, much research has been conducted to elucidate the molecular pathogenesis of fibroepithelial tumours, which, in turn, have allowed leveraging the findings for diagnostic applications, including grading of PTs. The most noteworthy discovery was of recurrent MED12 mutations in both fibroadenomas and PTs. Subsequent studies also uncovered relatively frequent genetic mutations in TERT promoter and RARA. A customised panel of 16 most frequently mutated genes in fibroepithelial tissues has been compiled previously and has contributed to resolving a few diagnostic dilemmas. This review will introduce the 16 genes and focus on the top three that are most frequently mutated in fibroepithelial tumours: MED12, TERT, and RARA.

A novel genomic panel as an adjunctive diagnostic tool for the characterization and profiling of breast Fibroepithelial lesions

Background

Known collectively as breast fibroepithelial lesions (FELs), the common fibroadenomas (FAs) and the rarer phyllodes tumors (PTs) are a heterogenous group of biphasic neoplasms. Owing to limited tissue availability, inter-observer variability, overlapping histological features and heterogeneity of these lesions, diagnosing them accurately on core biopsies is challenging. As the choice management option depends on the histological diagnosis; a novel 16-gene panel assay was developed to improve the accuracy of preoperative diagnosis on core biopsy specimens.

Methods

Using this 16-gene panel, targeted amplicon-based sequencing was performed on 275 formalin-fixed, paraffin-embedded (FFPE) breast FEL specimens, archived at the Singapore General Hospital, from 2008 to 2012.

Results

In total, 167 FAs, 24 benign, 14 borderline and 6 malignant PTs, were profiled. Compared to FAs, PTs had significantly higher mutation rates in the TERT promoter (p <  0.001), RARA (p <  0.001), FLNA, RB1 and TP53 (p = 0.002, 0.020 and 0.018, respectively). In addition to a higher mutational count (p <  0.001), TERT promoter (p <  0.001), frameshift, nonsense and splice site (p = 0.001, < 0.001 and 0.043, respectively) mutations were also frequently observed in PTs.

A multivariate logistic regression model was built using these as variables and a predictive scoring system was developed. It classifies a FEL at low or high risk (score <  1 and ≥ 1, respectively) of being a PT. This scoring system has good discrimination (ROC area = 0.773, 95% CI: 0.70 to 0.85), calibration (p = 0.945) and is significant in predicting PTs (p <  0.001).

Conclusion

This novel study demonstrates the ability to extract DNA of sufficient quality and quantity for targeted sequencing from FFPE breast core biopsy specimens, along with their successful characterization and profiling using our customized 16-gene panel. Prospective work includes validating the utility of this promising 16-gene panel assay as an adjunctive diagnostic tool in clinical practice.

The genomic mutation spectrums of breast fibroadenomas in Chinese population by whole exome sequencing analysis

Fibroadenomas (FAs) are the most common fibroepithelial lesions and the most common benign tumors of the breast in women of reproductive age. Although MED12 mutations, an overwhelming majority of all mutations, and some other gene mutations have been found in FAs, the genomic landscapes of FAs are still not completely clear and the genomic mutation spectrums of FAs in Chinese population remains unknown. Here, by performing whole exome sequencing of 12 FAs and the corresponding normal breast tissues in Chinese Han population, we observed the somatic and germline landscapes of genetic alterations. We identified 16 recurrently mutated genes with 37 nonsynonymous or frameshift somatic mutations and 27 recurrent somatic copy number variants (CNVs). In these mutated genes, MED12 was the most common in FAs, harboring 6 nonsynonymous/frameshift somatic mutations and 1 CNV. In addition, 6 germline mutations of tumor susceptibility genes in 5 FAs were identified and the tumor mutational burden of the 5 FAs was significantly higher than the other 7 FAs without germline mutations. This study provides genomic mutation spectrums of FAs in Chinese population and expand the genetic spectrum of FAs.

Artificial Intelligence and Digital Pathology: Challenges and Opportunities

In light of the recent success of artificial intelligence (AI) in computer vision applications, many researchers and physicians expect that AI would be able to assist in many tasks in digital pathology. Although opportunities are both manifest and tangible, there are clearly many challenges that need to be overcome in order to exploit the AI potentials in computational pathology. In this paper, we strive to provide a realistic account of all challenges and opportunities of adopting AI algorithms in digital pathology from both engineering and pathology perspectives.

Fibroepithelial lesions of the breast: a comprehensive morphological and outcome analysis of a large series

Mammary fibroepithelial lesions encompass a wide spectrum of tumors ranging from an indolent fibroadenoma to potentially fatal malignant phyllodes tumor. The criteria used for their classification based on morphological assessment are often challenging to apply and there is no consensus as to what constitutes an adequate resection margin. We studied a retrospective cohort of 213 fibroepithelial lesions in 178 patients (80 fibroadenomas with unusual features and 133 phyllodes tumors: 63 benign, 41 borderline, and 29 malignant) in order to describe the spectrum of changes within each group, with special emphasis on margin evaluation. Outcome data were available for 153 fibroepithelial lesions in 139 patients (median 56 months, range 3-249 months). Positive final margin (tumor transected), age < 50 years and a predominantly myxoid stroma were statistically significant predictors of local recurrence, while age > 50, stromal overgrowth, diffuse marked atypia, necrosis and mitotic index of ≥ 10 per 10 HPF were predictive of distant metastases. Tumors with satellite/bulging nodules were at a significantly higher risk to have a final positive resection margin. Our findings highlight important aspects of the interpretation and reporting of fibroepithelial lesions: the amount of myxoid stroma and the presence of satellite nodules are clinically relevant and should be routinely assessed and reported; infiltrative border might not be a prerequisite for the diagnosis of malignant phyllodes tumor, while the presence of tumor necrosis, massive stromal overgrowth or mitotic index of ≥ 25 per 10 HPF is diagnostic of malignant phyllodes tumor. On the other hand, increased mitotic index outside of the range of the World Health Organization guidelines in the absence of other worrisome features should be treated with caution, as it can be found in benign tumors.

MuDeRN: Multi-category classification of breast histopathological image using deep residual networks

MOTIVATION

Identifying carcinoma subtype can help to select appropriate treatment options and determining the subtype of benign lesions can be beneficial to estimate the patients' risk of developing cancer in the future. Pathologists' assessment of lesion subtypes is considered as the gold standard, however, sometimes strong disagreements among pathologists for distinction among lesion subtypes have been previously reported in the literature.

OBJECTIVE

To propose a framework for classifying hematoxylin-eosin stained breast digital slides either as benign or cancer, and then categorizing cancer and benign cases into four different subtypes each.

MATERIALS AND METHODS

We used data from a publicly available database (BreakHis) of 81 patients where each patient had images at four magnification factors (×40, ×100, ×200, and ×400) available, for a total of 7786 images. The proposed framework, called MuDeRN (MUlti-category classification of breast histopathological image using DEep Residual Networks) consisted of two stages. In the first stage, for each magnification factor, a deep residual network (ResNet) with 152 layers has been trained for classifying patches from the images as benign or malignant. In the next stage, the images classified as malignant were subdivided into four cancer subcategories and those categorized as benign were classified into four subtypes. Finally, the diagnosis for each patient was made by combining outputs of ResNets' processed images in different magnification factors using a meta-decision tree.

RESULTS

For the malignant/benign classification of images, MuDeRN's first stage achieved correct classification rates (CCR) of 98.52%, 97.90%, 98.33%, and 97.66% in ×40, ×100, ×200, and ×400 magnification factors respectively. For eight-class categorization of images based on the output of MuDeRN's both stages, CCRs in four magnification factors were 95.40%, 94.90%, 95.70%, and 94.60%. Finally, for making patient-level diagnosis, MuDeRN achieved a CCR of 96.25% for eight-class categorization.

CONCLUSIONS

MuDeRN can be helpful in the categorization of breast lesions.

Interobserver variation in the diagnosis of fibroepithelial lesions of the breast: a multicentre audit by digital pathology

Aim

Fibroepithelial lesions (FELs) of the breast span a morphological continuum including lesions where distinction between cellular fibroadenoma (FA) and benign phyllodes tumour (PT) is difficult. The distinction is clinically important with FAs managed conservatively while equivocal lesions and PTs are managed with surgery. We sought to audit core biopsy diagnoses of equivocal FELs by digital pathology and to investigate whether digital point counting is useful in clarifying FEL diagnoses.

Method

Scanned slide images from cores and subsequent excisions of 69 equivocal FELs were examined in a multicentre audit by eight pathologists to determine the agreement and accuracy of core needle biopsy (CNB) diagnoses and by digital point counting of stromal cellularity and expansion to determine if classification could be improved.

Results

Interobserver variation was high on CNB with a unanimous diagnosis from all pathologists in only eight cases of FA, diagnoses of both FA and PT on the same CNB in 15 and a ‘weak’ mean kappa agreement between pathologists (k=0.36). ‘Moderate’ agreement was observed on CNBs among breast specialists (k=0.44) and on excision samples (k=0.49). Up to 23% of lesions confidently diagnosed as FA on CNB were PT on excision and up to 30% of lesions confidently diagnosed as PT on CNB were FA on excision. Digital point counting did not aid in the classification of FELs.

Conclusion

Accurate and reproducible diagnosis of equivocal FELs is difficult, particularly on CNB, resulting in poor interobserver agreement and suboptimal accuracy. Given the diagnostic difficulty, and surgical implications, equivocal FELs should be reported in consultation with experienced breast pathologists as a small number of benign FAs can be selected out from equivocal lesions.

Fine-needle versus core-needle biopsy - which one to choose in preoperative assessment of focal lesions in the breasts? Literature review

Aim

The aim of the study was to review two techniques that can be used to verify focal lesions in the breasts: fine-needle aspiration biopsy and core-needle biopsy.

Material and methods

Fifty-five articles (original papers and reviews), half of them published within the past 5 years, were included in the analysis. The authors also took their own experience into account.

Results

Pre-operative assessment of focal lesions in the breasts is crucial in the planning of further therapeutic management. The role of fine-needle aspiration biopsy has been reduced lately due to its low sensitivity and specificity as well as a high rate of non-diagnostic, suspicious and false negative results. This method does not enable one to differentiate between in situ and invasive disease. Currently, fine-needle biopsy is recommended for cystic lesions, suspected of being recurrences in the chest wall, and lymph node metastases. Core-needle biopsy is the basic diagnostic method of breast lesions. According to the recommendations of the Polish Ultrasound Society and American College of Radiology, BIRADS 4 and 5 lesions should be evaluated histopathologically. Core-needle biopsy makes it possible to establish a final diagnosis more frequently than fine-needle biopsy, both in the case of benign and malignant lesions. It delivers more information about the nature of a tumor (mutation of HER-2, estrogen and progesterone receptors and Ki-67 index). Its limitations include: underestimation of invasion and failure to recognize the components of ductal carcinoma in situ in papillary and atypical lesions. Single fine-needle aspiration biopsy is inexpensive, but when considering the cost of further diagnosis due to non-diagnostic, suspicious and atypical results, this method generates high additional costs.

Conclusions

Microscopic verification of focal breast lesions is crucial for further therapeutic decisions. It has been proven that histopathological verification is more accurate and has more advantages than cytological assessment.

Genetics and genomics of breast fibroadenomas

Fibroadenomas of the breast are benign fibroepithelial tumours most frequently encountered in women of reproductive age, although they may be diagnosed at any age. The fibroadenoma comprises a proliferation of both stromal and epithelial components. The mechanisms underlying fibroadenoma pathogenesis remain incompletely understood. In the clinical setting, distinguishing cellular fibroadenomas from benign phyllodes tumours is a common diagnostic challenge due to subjective histopathological criteria and interobserver differences. Recent sequencing studies have demonstrated the presence of highly recurrent mutations in fibroadenomas, and also delineated the genomic landscapes of fibroadenomas and the closely related phyllodes tumours, revealing differences at the gene level, which may be of potential adjunctive diagnostic use. The present article provides an overview of key studies uncovering genetic and genomic abnormalities in fibroadenomas, from initial karyotype reports revealing myriad cytogenetic aberrations to next-generation sequencing-based approaches that led to the discovery of highly recurrent MED12 mutations. A thorough understanding of these abnormalities is important to further elucidate the mechanisms by which fibroadenomas arise and to refine diagnostic assessment of this very common tumour.

A Diagnostic Approach to Fibroepithelial Breast Lesions

Fibroepithelial breast lesions encompass a heterogeneous group of neoplasms that range from benign to malignant, each exhibiting differing degrees of stromal proliferation in relation to the epithelial compartment. Fibroadenomas are common benign neoplasms that may be treated conservatively. Phyllodes tumors are relatively rare lesions, and classified as benign, borderline, or malignant based on histologic evaluation of various parameters. The diagnostic interpretation of "gray-zone" fibroepithelial lesions often imposes formidable demands on a pathologist's skills. This article offers practical recommendations for the diagnostic workup of these lesions, including the appropriate utilization of ancillary investigations and the approach to core needle biopsies.

Lipomatous tumors of the breast: A contemporary review

Breast tumors with lipomatous or liposarcomatous components are infrequently encountered, but can be a source of diagnostic difficulty if the context of the fatty differentiation is not recognized. Among the true adipocytic tumors, lipoma is the most common lipomatous tumor arising in the breast. Several mammary spindle cell tumors may show adipocytic differentiation, including fibroepithelial tumors and myofibroblastoma. Liposarcomatous components most often arise in malignant phyllodes tumors, as opposed to primary liposarcomas of the breast which are believed to be uncommon. This article will review the spectrum fat-containing tumors of the breast with an emphasis on differential diagnosis and insights from recent molecular studies.