Breast Pathology Research Articles

Variability in the diagnosis and reporting of metaplastic breast carcinoma: results of an international survey.

Metaplastic breast carcinoma (MBC) is a heterogeneous group of invasive breast carcinoma with squamous, spindle cell, or mesenchymal elements. It may be monophasic or biphasic, and often coexists with invasive breast carcinoma of no special type (IBC-NST). Currently, there are no standardized guidelines for reporting MBC, and a diagnostic threshold for the metaplastic component is not established by the WHO classification. A survey conducted from April-July 2023 gathered responses from 44 pathologists worldwide. Most respondents were academic breast pathologists, and attended weekly breast tumour boards. The criteria for diagnosing MBC were highly varied, with cutoffs ranging from any/<10% to >90% metaplastic component. Although 90% was the most common threshold used, only 25% of respondents applied it. Pathologists generally preferred diagnosing invasive carcinoma with mixed features when the metaplastic component was ≤50% and MBC when the metaplastic component >50%. Most pathologists reported both the type and percentage of metaplastic component. In all, 43% reported core biopsy and resection specimen with different approaches. Diagnostic guidelines reportedly used (if any) were highly varied. The study underscores the need for standardized guidelines for MBC. Without clear and established diagnostic criteria, current data on MBC remains inconsistent and hinders further research into the clinical significance and prognostic implications of the metaplastic component.

Whole mount preparation and analysis of rabbit mammary gland

The mammary gland undergoes dynamic structural and compositional changes throughout life, influenced significantly by hormonal fluctuations and environmental factors. From embryonic development through menopause, this tissue adapts to accommodate phases such as postnatal expansion, pregnancy-induced lactation, and post-weaning involution. Hormones, growth factors, cytokines, and exogenous factors regulate these innate processes, affecting mammary epithelial cell proliferation and sensitivity, particularly in terminal end buds (TEB) and lobules, which are highly susceptible to endocrine disruption. Rodent models have provided invaluable insights into mammary gland biology, yet differences exist compared to human development, prompting the exploration of alternative models like rabbits. Additionally, there is momentum to move away from the use of nonhuman primates in safety assessments, increasing the need for evaluation tools for all tissues in the rabbit model. Rabbit mammary glands exhibit similarities to humans, making them promising for studying breast biology and pathology. However, protocols for whole-mount analysis of rabbit mammary glands are lacking due to the technical challenges of working with thicker tissue than rodent mammary glands. Here, we developed a methodology modified from rodent studies for preparing and analyzing rabbit mammary gland whole mounts, which is essential for advancing research in mammary gland biology and understanding the effects of hormonal and toxicant-induced disruption of mammary gland growth and function.

Application of artificial intelligence in the field of breast pathology diagnosis: narrative review

Application of artificial intelligence in the field of breast pathology diagnosis: narrative review

Ultrasonography in gynecomastia diagnosis: Clinical experience

Aim. To analyze the applicability of ultrasonography in gynecomastia diagnosis. Materials and methods. The study included 119 males aged 18 to 74 years with complaints of a lump in the projection of the areola, and/or pain/discomfort in the breast gland area. All the patients underwent an ultrasound examination (US) of the breast. In 112 (94.05%) patients, US revealed changes typical of gynecomastia. All patients were divided into three age groups: 18–44 years (n = 99), 45–59 years (n = 15), 60–74 years (n = 5). Results. Out of 112 cases, 97 and 15 were identified as gynecomastia and pseudogynecomastia, respectively. The highest incidence of gynecomastia was observed in the first age group, with peaks at 24–26 and 30–32 years. Gynecomastia was more often defined as bilateral (67%); unilateral gynecomastia was found in 21.6% and 11.4% of cases on the left and right breast, respectively. The average diameter of the glandular disc was not statistically different in the studied groups (p &gt; 0.05, p = 0.5), while the thickness of the glandular layer was statistically significantly different and increased with age (p ≤ 0.05). The symptoms of true gynecomastia included: in 22 cases, pain and/or discomfort in the breast; in 37 cases, an increase in size; and in 38 cases, a combination of symptoms. Subcutaneous mastectomy on both sides was performed in 21 patients. Histologically, the fibrous stage of gynecomastia predominated in 85.7% of cases (n = 18), the intermediate stage accounted for 9.5% of cases (n = 2), and the flowering stage was noted in 4.8% of cases (n = 1). The US diagnostic efficacy was determined as follows: specificity 100%, accuracy 96.3%, and sensitivity 95.45%.Conclusion. Ultrasound examination is an accessible, non-invasive, and safe diagnostic method for patients with suspected breast pathology.

Report of the Gynaecological and Breast Pathology Working Group of the German Society of Pathology : 2024 DGP Annual Conference

Report of the Gynaecological and Breast Pathology Working Group of the German Society of Pathology : 2024 DGP Annual Conference

Research progress of breast pathology image diagnosis based on deep learning

Breast cancer is a malignancy caused by the abnormal proliferation of breast epithelial cells, predominantly affecting female patients, and it is commonly diagnosed using histopathological images. Currently, deep learning techniques have made significant breakthroughs in medical image processing, outperforming traditional detection methods in breast cancer pathology classification tasks. This paper first reviewed the advances in applying deep learning to breast pathology images, focusing on three key areas: multi-scale feature extraction, cellular feature analysis, and classification. Next, it summarized the advantages of multimodal data fusion methods for breast pathology images. Finally, the study discussed the challenges and future prospects of deep learning in breast cancer pathology image diagnosis, providing important guidance for advancing the use of deep learning in breast diagnosis.

Unveiling a Surgical Revolution: The Use of Conventional Histology versus Ex Vivo Fusion Confocal Microscopy in Breast Cancer Surgery.

Ex vivo fusion confocal microscopy (EVFCM) enables the rapid examination of breast tissue and has the potential to reduce the surgical margins and the necessity for further surgeries. Traditional methods, such as frozen section analysis, are limited by the distortion of tissue and artefacts, leading to false negatives and the need for additional surgeries. This study on observational diagnostic accuracy evaluated the ability of EVFCM to detect breast cancer. A total of 36 breast tissue samples, comprising 20 non-neoplastic and 16 neoplastic cases, were analysed using EVFCM and compared to the results obtained from routine histopathology. A Mohs surgeon experienced in EVFCM (evaluator A) and two breast pathologists unfamiliar with EVFCM (evaluators B and C) performed blinded analyses. EVFCM showed high concordance with the histopathology and the detection of neoplasia, with significant kappa values (p < 0.001). Evaluator A achieved 100% sensitivity and specificity. Evaluators B and C achieved a sensitivity of >87%, a specificity of >94%, positive predictive values of >95%, and negative predictive values of 81% and 94%, respectively. EVFCM therefore offers a promising technique for the assessment of margins in breast-conserving surgery. Its widespread adoption could significantly reduce re-excisions, lower healthcare costs, and improve cosmetic and oncological outcomes.

Fully Automated Artificial Intelligence Solution for Human Epidermal Growth Factor Receptor 2 Immunohistochemistry Scoring in Breast Cancer: A Multireader Study.

The proven efficacy of human epidermal growth factor receptor 2 (HER2) antibody-drug conjugate therapy for treating HER2-low breast cancers necessitates more accurate and reproducible HER2 immunohistochemistry (IHC) scoring. We aimed to validate performance and utility of a fully automated artificial intelligence (AI) solution for interpreting HER2 IHC in breast carcinoma. A two-arm multireader study of 120 HER2 IHC whole-slide images from four sites assessed HER2 scoring by four surgical pathologists without and with the aid of an AI HER2 solution. Both arms were compared with high-confidence ground truth (GT) established by agreement of at least four of five breast pathology subspecialists according to ASCO/College of American Pathologists (CAP) 2018/2023 guidelines. The mean interobserver agreement among GT pathologists across all HER2 scores was 72.4% (N = 120). The AI solution demonstrated high accuracy for HER2 scoring, with 92.1% agreement on slides with high confidence GT (n = 92). The use of the AI tool led to improved performance by readers, interobserver agreement increased from 75.0% for digital manual read to 83.7% for AI-assisted review, and scoring accuracy improved from 85.3% to 88.0%. For the distinction of HER2 0 from 1+ cases (n = 58), pathologists supported by AI showed significantly higher interobserver agreement (69.8% without AI v 87.4% with AI) and accuracy (81.9% without AI v 88.8% with AI). This study demonstrated utility of a fully automated AI solution to aid in scoring HER2 IHC accurately according to ASCO/CAP 2018/2023 guidelines. Pathologists supported by AI showed improvements in HER2 IHC scoring consistency and accuracy, especially for distinguishing HER2 0 from 1+ cases. This AI solution could be used by pathologists as a decision support tool for enhancing reproducibility and consistency of HER2 scoring and particularly for identifying HER2-low breast cancers.

Effective detection of breast pathology using machine learning methods

Effective detection of breast pathology using machine learning methods

An approach to determine pathological breast tissue samples with free‐space measurement method at 24 GHz

AbstractPathology is an important branch of science in the diagnosis and treatment of several diseases. In cancer diseases, serious investigations have been made about the course of the diseases. A report that is essential for both the patient and the doctor is prepared by the pathologists as a result of a detailed cellular examination. These reports contain information about the disease. Access duration to these reports, which affects the form and duration of the treatment, is extremely important today. It is possible to shorten this period with systems using antenna technologies. The pathological breast tissue samples have been examined by using horn antenna structures with high gain in this study. Dual identical horn antennas have been placed opposite each other as receivers and transmitters in the measurement setup at 24 GHz. Measurements of normal and cancerous breast tissues have been made, and the normalization process has been applied to the measured scattering parameters. The different values between normal and cancerous breast tissues have been shown with this process. The normalized values are compared with other analyzed values. According to the results obtained, the percentage of normalized values for transmission is much more effective and meaningful than other results.

Concordance of PD-L1 Expression in Metastatic Triple-negative Breast Cancer Between the 22C3 and E1L3N Antibodies Using Combined Positive Scoring.

For patients with metastatic triple-negative breast cancer (TNBC), treatment with pembrolizumab is dependent on the accurate determination of programmed death ligand 1 (PD-L1) expression using immunohistochemistry (IHC). This study evaluated the interobserver concordance in assessing PD-L1 expression on TNBC samples using the commercial 22C3 IHC assay and an in-house assay based on the E1L3N antibody. Concordance between the 22C3 and the E1L3N IHC assays was evaluated on TNBC samples read by a commercial laboratory and a Brigham and Women's Hospital breast pathologist (BWH reader). Each slide was given a PD-L1 combined positive score (CPS) and was considered PD-L1 positive or negative based on the CPS cutoff of 10. Interobserver concordance for the assays was also evaluated on a subset of samples between 2 and 3 independent readers. On 71 samples, 2 independent readers (1 BWH reader and commercial laboratory) using E1L3N and 22C3, respectively, reached agreement on PD-L1 status (positive/negative) on 64 samples (90.1%). Using 22C3, 2 independent readers reached agreement on PD-L1 status on 30 of 36 samples (83.3%), and 3 independent readers reached agreement on 16 of 27 samples (59.3%). Using E1L3N, 2 BWH readers reached agreement on PD-L1 status on 18 of 27 samples (66.7%). Three BWH readers reached an agreement on 2 of 12 of the most challenging samples (16.7%). In conclusion, concordance between E1L3N and 22C3 testing using CPS for PD-L1 in metastatic TNBC was >90%. However, certain cases were challenging to agree upon using current threshold criteria, highlighting the need for more standardized evidence-based methods to assess PD-L1 expression.

Challenges and improvements in HER2 scoring and histologic evaluation: insights from a national proficiency testing scheme for breast cancer diagnosis in China

BackgroundIn 2022, our team launched the pioneering national proficiency testing (PT) scheme for the pathological diagnosis of breast cancer, rapidly establishing its credibility throughout China. Aiming to continuously monitor and improve the proficiency of Chinese pathologists in breast pathology, the second round of the PT scheme was initiated in 2023, which will expand the number of participating institutions, and will conduct a nationwide investigation into the interpretation of HER2 0, 1+, and 2+/FISH- categories in China.MethodsThe methodology employed in the current round of PT scheme closely mirrors that of the preceding cycle in 2022, which is designed and implemented according to the “Conformity assessment—General requirements for proficiency testing”(GB/T27043—2012/ISO/IEC 17043:2010). More importantly, we utilized a statistics-based method to generate assigned values to enhance their robustness and credibility.ResultsThe final PT results, published on the website of the National Quality Control Center for Cancer (http://117.133.40.88:3927), showed that all participants passed the testing. However, a few institutions demonstrated systemic biases in scoring HER2 0, 1+, and 2+/FISH- with accuracy levels below 59%, considered unsatisfactory. Especially, the concordance rate for HER2 0 cases was only 78.1%, indicating challenges in distinguishing HER2 0 from low HER2 expression. Meanwhile, areas for histologic type and grade interpretation improvement were also noted.ConclusionsOur PT scheme demonstrated high proficiency in diagnosing breast cancer in China. But it also identified systemic biases in scoring HER2 0, 1+, and 2+/FISH- at some institutions. More importantly, our study highlighted challenges in the evaluation at the extreme lower end of the HER2 staining spectrum, a crucial area for further research. Meanwhile, it also revealed the need for improvements in interpreting histologic types and grades. These findings strengthened the importance of robust quality assurance mechanisms, like the nationwide PT scheme conducted in this study, to maintain high diagnostic standards and identify areas requiring further training and enhancement.

Enhanced Differentiation of Amiodarone-Induced Thyrotoxicosis Types Using Semi-Quantitative 99mTc-MIBI Uptake Analysis: A Pilot Study.

BACKGROUND Technetium (99mTc)-labelled Methoxy-2-Isobutylisonitrile (MIBI) is a diagnostic lipophilic cationic radiotracer used to evaluate the cardiac, breast, thyroid, and parathyroid pathology. This study aimed to evaluate the role of MIBI combined with Tc-99m pertechnetate thyroid scintigraphy, thyroid ultrasonography, and measurement of thyrotropin, thyroid hormones, and autoantibodies to subtype amiodarone-induced thyrotoxicosis (AIT) and the contribution of semi-quantitative analysis of MIBI uptake. MATERIAL AND METHODS This cross-sectional study included 36 patients with AIT who underwent thyrotropin, thyroid hormone, and autoantibody analysis using chemiluminescent method, ultrasonography, pertechnetate, and MIBI thyroid scintigraphy with semi-quantitative uptake, including calculation of the target-to-background ratio (TBR) with 2 different background regions. The MIBI washout rate (WR) was analyzed in all groups. Statistical analysis was performed using descriptive statistics, correlations, and the receiver operating characteristic curve - area under the curve (ROC-AUC). The results were compared with the control group. RESULTS Based on visual and semi-quantitative analyses, patients were successfully categorized into AIT groups (AIT-1, AIT-2 and AIT-3) but the latter method enabled better differentiation of MIBI uptake between all groups. Additionally, ROC-AUC analysis determined cutoff values which enabled discerning between AIT-1 and AIT-2 groups, and AIT-1 and AIT-3 groups. WR showed no significant difference between all AIT groups and controls (P>0.05). CONCLUSIONS Visual MIBI analysis enabled differentiation between AIT-1 and 2 groups, but the method was substantially improved with semi-quantitative analysis, especially in defining AIT-3 group. However, multicenter collaboration with larger studies is needed to standardize the method and obtain more accurate and consistent results.

Helping patients navigate the immediate release of medical records: MedEd, a novel patient engagement technology

BackgroundThrough online health portals, patients receive complex medical reports without interpretation from their healthcare provider. This study evaluated the usability of MedEd, a patient engagement tool providing definitions of medical terminology in breast pathology and radiology reports. MethodsIndividuals who underwent a normal screening mammogram were invited to complete semi-structured interviews where they downloaded MedEd and discussed their download experience. Acceptability, appropriateness, and feasibility of MedEd were evaluated. Results143 individuals were invited to participate, and 14 semi-structured interviews were completed. Participants reported ease of downloading and navigating MedEd with concerns about privacy and others’ abilities to download. Participants demonstrated high acceptability (mean 4.48/5, SD 0.95), appropriateness (mean 4.66/5, SD 0.83), and feasibility (mean 4.48/5, SD 1.04) scores. ConclusionParticipants expressed excitement for future use of MedEd and provided suggestions for improvements. Next steps include evaluating comprehension of real breast reports while using MedEd and expanding patient access.

Vacuum aspiration biopsy: evolution of the method, prevention of hemorrhagic complications

In Russia, more than 70,000 new cases of breast cancer are registered annually. Vacuum aspiration biopsy (VAB) is a minimally invasive method for diagnosing the genesis of focal breast pathology, which is also used for therapeutic purposes for the complete removal of benign neoplasms. High efficiency and favorable clinical outcomes have allowed VAB to gain wide popularity in clinical practice, due to which the method has been widely developed. However, like any surgical intervention, the VAB procedure may be accompanied by complications, the main share of which are hemorrhagic. Generalization and systematization of information on the development of the VAB technique, prevalence and risk factors of complications, as well as methods of their prevention and timely elimination. Scientific publications cited in this literature review were selected from the Pubmed database of medical and biological publications (National Center for Biotechnology Information (NCBI), USA), the Clinical Key database (Elsevier Corporation, the Netherlands), Web of Science Citation Indexing Database (Clarivate, USA), Google Scholar (CIF), and the scientific electronic library elibrary.ru (Russia). The information presented in the article can become a theoretical basis for future research aimed at increasing safety, further development and improvement of the VAB technique.

Zinc transporter ZnT5 is associated with epithelial mesenchymal transition via SMAD1 in breast cancer.

Zinc levels in breast cancer tissues have been reported to be higher than those in normal tissues. In addition, the expression levels of zinc transporters, including ZnT5 and ZnT6, are reportedly higher in breast cancer than in normal breast tissues. ZnT5 and ZnT6 also contribute to heterodimer formation and are involved in several biological functions. However, the functions of ZnT5 and ZnT6 heterodimers in breast cancer remain unknown. Therefore, we first investigated the immunolocalization of ZnT5 and ZnT6 in pathological breast cancer specimens and in MCF-7 and T-47D breast cancer cells. Next, we used small interfering RNA to assess cell viability and migration in ZnT5 knockdown MCF-7 and T-47D cells. Immunohistochemical analysis showed that the number of ZnT5-positive breast cancer cells was inversely correlated with the pathologic N factor status. ZnT5 knockdown had no effect on cell viability in the presence of 100 μM ZnCl2 in MCF-7 and T-47D cells. In a wound healing assay, 100 μM ZnCl2 treatment inhibited cell migration of MCF-7 and T-47D cells, whereas ZnT5 knockdown promoted cell migration, decreased E-cadherin expression and increased vimentin, slug and matrix metalloproteinase 9 expression. Antibody arrays showed that ZnT5 knockdown increased the expression of SMAD1, and that dorsomorphin treatment inhibited the promotion of migratory ability induced by ZnT5 knockdown. The results of this study revealed that both ZnT5 may be involved in less aggressive breast cancer subtypes, possibly through inhibition of cell migration.

Feasibility and Accuracy of Ultrasound-Guided Core Needle Biopsy for Nipple Lesions: A Pilot Study.

Due to the superficial location, suspicious findings of the nipple-areolar complex (NAC) are not amenable to stereotactic or MRI-guided sampling and have historically necessitated surgical biopsy or skin-punch biopsy. There are limited reports of US-guided core biopsy of the nipple (US-CBN). We report our nearly 3-year pilot experience with US-CBN at an academic breast imaging center. An institutional review board-exempt and HIPAA-compliant retrospective review was performed. We assessed patient demographics, breast imaging characteristics, procedural data, pathology, and outcomes. Nine female patients aged 27 to 64 underwent US-CBN from January 2021 to October 2023. Initial imaging abnormalities included abnormal MRI enhancement, mammographic calcifications, and sonographic masses. After initial or second-look US, all imaging findings had sonographic correlates for biopsy specimens, the majority of which were sonographic masses (8/9). US-CBN was performed by 6 breast radiologists using a variety of devices. All biopsy specimen results were concordant with sonographic abnormalities, although 1 was considered discordant from the initial abnormality seen on MRI. There were no complications, and discomfort during the procedure was well-treated. Two patients (22%, 2/9) were diagnosed with malignancy. This pilot study demonstrated that US-CBN can be performed by a breast radiologist for definitive diagnosis of suspicious nipple abnormalities seen on breast imaging, avoiding surgery, and maintaining nipple integrity. In our population, 22% (2/9) of US-CBNs revealed malignancy.

Incidence of High Risk and Malignant Pathological Findings in Transgender and Gender Diverse Individuals Undergoing Gender-Affirming Mastectomy

BackgroundConcrete, data-driven guidelines for breast cancer screening among the transgender and gender diverse (TGD) population is lacking. The present study evaluates possible associations of gender-affirming hormone therapy (GAHT) on incidental breast pathology findings in trans-masculine patients to inform decision making about breast cancer screening.Patients and MethodsThis was a retrospective cohort study of patients who had gender-affirming mastectomy or breast reduction at a single center from July 2019 to February 2024. A total of 865 patients met the inclusion criteria. Gender-affirming testosterone therapy and length of exposure were evaluated to seek differences in post-operative pathology findings.ResultsThe median age at the time of surgery was 27 years [interquartile range (IQR) 21–30]. Most participants identified as female to male (658, 75.6%). A significant portion of the participants (688, 79.2%) were undergoing testosterone therapy at the time of surgery, with the median duration of testosterone use prior to surgery being 14 months (IQR 4–29). High risk or malignant findings were noted in pathology results for 12 of 1730 breasts (0.7%). Ordered logistic regression found that duration of testosterone therapy was not associated with increasing severity of incidental breast pathology. Additionally, patients under 25 years of age were 70% less likely to have any incidental finding on pathological evaluation than older patients [odds ratio (OR) 0.3, p < 0.01, confidence interval (CI) 0.18–0.50].ConclusionsThe present study found that patients undergoing GAHT should not be screened for breast cancer with increased frequency compared with cis-gender women. Additionally, it may be appropriate for trans women under the age of 25 with normal breast cancer risk to forego pathological breast tissue examination.

Granulomatous mastitis and other inflammatory mastitis simulating breast neoplasms – A retrospective study in the fine needle aspiration cytology clinic of a tertiary care center in eastern India

Background: Fine needle aspiration cytology (FNAC) is an important diagnostic modality in palpable breast lesions. This together with imaging modality is important in distinguishing benign from malignant lesions of the breast. Granulomatous/inflammatory mastitis forms a small subset of breast lesions that may present as a breast lump. Clinical and radiological features in these cases may mimic malignant breast pathology. Aims and Objectives: The aim of this study was to study the frequency of granulomatous mastitis and other inflammatory mastitis with respect to other neoplastic lesions of the breast, presented in FNAC clinics and to correlate the cytological findings with the clinical presentation of granulomatous and other inflammatory mastitis. Materials and Methods: A retrospective study was conducted in the Department of Pathology in a tertiary care center in Eastern India for duration of 4 years 5 months. Details of all patients who underwent FNAC for breast lesions during the study period were recorded in terms of their clinical presentation, cytological findings, imaging, and ancillary investigations. The findings were then tabulated in a master sheet and analysis done by descriptive statistics using SPSS 25. Results: A total of 154 cases were included with 5 cases (3.2%) of granulomatous and 12 cases (7.8%) of inflammatory mastitis. Age range for granulomatous/inflammatory mastitis was 20–70 years. Lump and pain were the most common complaints followed by inflammatory skin changes and nipple discharge. Very few cases also showed nipple retractions and very occasional systemic symptoms like fever. History of lactation was seen among five cases. Three cases showed positive acid-fast bacilli in Ziehl–Neelsen stain. Radiology was discordant with cytological findings in three cases, where the former suggested a breast neoplastic process. Conclusion: Granulomatous/inflammatory mastitis is a rarely diagnosed entity in breast cytopathology with no standard guidelines for management. Antibiotics antitubercular therapy and corticosteroids are some proposed lines of medical management. In treatment-resistant cases, wide local excision may be done depending on available resources and surveillance opportunities.

Malignant Phyllodes Tumour with Heterologous Osteosarcomatous differentiation and Osteoclast-like giant cells: Case Report of an uncommon neoplasm

Background: Phyllodes tumour (PT), an uncommon fibroepithelial neoplasm accounts for less than 1% of all primary tumours of the breast. MPT with osseous differentiation often gets misdiagnosed on imaging as benign giant calcifications resulting in treatment delay. We describe a rare case of MPT with heterologous osteosarcomatous differentiation and osteoclast-like giant cells and review the literature to discuss clinical-radiological findings, differential diagnosis and treatment options. Case Presentation: A 34-year-old female presented with a right breast lump. Mammography showed a high-density irregular mass with amorphous dense calcification, suggesting neoplastic aetiology. Preoperative core needle biopsy raised the possibility of a phyllodes tumour versus giant cell tumour. Wide local excision was performed to confirm the diagnosis which revealed the presence of a biphasic tumour with osteoid-like matrix and numerous osteoclastic giant cells. Immunohistochemistry was used to rule out metaplastic carcinoma or carcinosarcoma. The stromal cells were negative for panCK and P63 and positive for vimentin, CD10 and BCL-2. The osseous component was positive for Osteonectin and SATB2. Thus, a final diagnosis of malignant phyllodes tumour with heterologous osteosarcomatous differentiation and osteoclast-like giant cells was made. Conclusion: MPT with osteosarcomatous differentiation is a rare and challenging entity associated with a poor clinical outcome. Accurate diagnosis requires a multidisciplinary approach involving breast surgeons, pathologists and radiologists with careful histopathological examination. Wide local excision with close surveillance is crucial for timely detection of tumour recurrence and metastasis.