Brystkreft hos menn ­ histopatologi og biomarkører.

Background: Breast cancer in men accounts for around 1 % of all cases of the disease. The study aimed to identify histopathological parameters and selected biomarkers in men with breast cancer. Material and method: Retrospective study of archival material from 53 men diagnosed with breast cancer at the department of pathology, Haukeland University Hospital, in the period 1996-2020. The prevalence of the oestrogen receptor (ER), progesterone receptor (PGR) and Human Epidermal Growth Factor (HER2) biomarkers was examined. Results: Median age at time of diagnosis was 72 years. Median tumour diameter was 24 mm. Forty-nine tumours were classified histologically as invasive carcinoma of no special type (NST), 29 tumours were histologic grade 2 and 18 were grade 3. Fifty-two tumours were ER positive, 39 were PGR positive and four were HER2 positive. Twenty-five patients had lymph node metastases. Interpretation: Our findings indicate that men with breast cancer are diagnosed at an older age than women, and that men have a more advanced stage than women at the time of diagnosis. The histopathology and expression of biomarkers of breast cancer differ between men and women.

Experiences and perceptions of men following breast cancer diagnosis: a mixed method systematic review.

BACKGROUND: Men with breast cancer experience unique physical and emotional challenges. However, a thorough understanding of these experiences including the psychosocial effects and supportive care needs have received less attention. In some settings, men with breast cancer experience stigma within the healthcare system and their care needs are not prioritised. This influences the level of professional support offered, consequently worsening their health and well-being outcomes. This review explored the variabilities in the experiences and treatment modalities of male breast cancer (MBC) across different contexts. METHODS: All primary study designs including qualitative, quantitative, and mixed methods studies that reported on the experiences, treatment approaches and outcomes of MBC were included in this systematic review. Six databases (Embase, Medline, PsycINFO, Global Health, CINAHL and Web of Science) were searched for articles from January 2000 to September 2023. A results-based convergence synthesis was used for data analysis and reported using PRISMA guidelines. RESULTS: Of the studies screened (n = 29,687), forty-four fulfilled the predetermined criteria and were included. Our findings relating to the experiences and treatment approaches of MBC are broadly themed into three parts. Theme 1-Navigating through a threat to masculinity: describes how males experienced the illness reflecting on detection, diagnosis, coming to terms with breast cancer, and disclosure. Theme 2- Navigating through treatment: captures the experiences of undergoing breast cancer treatment/ management following their diagnosis. Theme 3-Coping and support systems: describes how MBC patients coped with the disease, treatment process, aftercare/rehabilitative care, and the available support structures. CONCLUSIONS: Men experience a myriad of issues following a breast cancer diagnosis, especially with their masculinity. Awareness creation efforts of MBC among the public and healthcare practitioners are urgently required, which could change the perception of men in promoting early diagnosis, adherence to treatments, post-treatment monitoring, oncological results and a better quality of life. Considerations for training, education and development of specialised guidelines for healthcare practitioners on MBC would provide the necessary knowledge and skills to enhance their practice through the adoption of person-centred and male-specific care strategies. Professional care intervention and support for MBC should not end after the diagnosis phase but should extend to the entire treatment continuum and aftercare including future research focusing on MBC specific clinical trials. TRIAL REGISTRATION: PROSPERO Registration No. CRD42021228778.

Male Breast Cancer: a Review on Diagnosis, Treatment, and Survivorship.

PURPOSE OF REVIEW: Male breast cancer is a relatively uncommon and rare disease that is often managed based on evidence adopted from trials pertaining to female breast cancer due to low accrual rates or exclusion of males. This is despite the known differences in the biology and epidemiology of this condition. This review provides an update regarding the management and surveillance of male breast cancer. RECENT FINDINGS: Men with breast cancer tend to undergo more extensive surgery in the breast and axilla. The outcomes of male breast cancer compared to a similar subtype of female breast cancer appear worse when matched for stage. Systemic therapies remain predominantly based on recommendations for female breast cancer, although tamoxifen is the more optimal endocrine therapy for men than women. Surveillance with mammograms is recommended for patients harboring a breast cancer susceptibility gene but is otherwise not advised for men who have undergone a mastectomy. Notably, the role of other imaging modalities, including ultrasound and magnetic resonance imaging, is minimal. Although the focus on survivorship care among men is low, it is abundantly clear that this is a stigmatizing diagnosis for men, and they suffer from long-term physical and psychological sequelae following a diagnosis and treatment of breast cancer. In summary, providing more gender-inclusive care and advocating for increased representation of men in prospective breast cancer studies and clinical trials may help improve outcomes and provide enhanced support for this population.

Management of Male Patients With Occult Breast Cancer: Analysis of the National Cancer Database.

INTRODUCTION: Occult breast cancer (OBC) consists of <0.1% of breast cancer cases in the United States. Male occult breast cancer (mOBC) has not been well-studied outside of case reports, and management is largely based on female OBC (fOBC) studies. We aim to examine the prevalence of mOBC among those in the National Cancer Database with breast cancer and describe treatment modalities received by mOBC compared to fOBC. METHODS: The National Cancer Database was queried for patients with OBC from 2004 to 2018. Chi-Square test and Fisher's exact tests compared patient, clinical, and facility characteristics by sex. Treatment modalities [systemic therapy, radiation therapy, axillary lymph node dissection, modified radical mastectomy (MRM)] were compared. A subgroup analysis examined pathologic upstaging in patients who underwent MRM. RESULTS: Of 23,374 male patients with breast cancer, 0.13% were identified to have mOBC [versus 0.09% in fOBC]. cN2/N3 disease was significantly more prevalent in the mOBC cohort (61.3%) than in the fOBC cohort (30.7%, P < 0.001). Receipt of axillary lymph node dissection or MRM was not significantly different by sex. Male OBC (mOBC) patients were less likely to receive trimodality treatment than fOBC patients. In patients who underwent MRM, more mOBC patients [75%] were pathologically upstaged as T+ after mastectomy than fOBC patients [30%, P < 0.001], questioning the adequacy of diagnostic workup for mOBC compared to fOBC. CONCLUSIONS: This review confirms mOBC as an extremely rare disease. Multimodal treatments have been highly utilized to optimize care in this patient population. Further investigation is warranted to examine the survival benefit of treatment regimens for mOBC.

Melanoma Mimicker: Pigmented Mammary Paget Disease in a Man.

ABSTRACT: Male breast cancer comprises less than 1% of all breast cancer cases. Mammary Paget disease (MPD) represents a subset of breast cancer that presents with skin changes of the nipple and areola, and is frequently misdiagnosed clinically due to similarities with other disease states, leading to an average delay in diagnosis of 1 month to 2 years. Pigmented mammary Paget disease (PMPD) is an uncommon variant of MPD that clinically and histologically resembles malignant melanoma. Due to variable immunohistochemical staining patterns, analysis can be challenging and often requires interpretation of panels for accurate diagnosis. We present a rare case of PMPD in a male, originally diagnosed both clinically and histologically as malignant melanoma, to highlight the diagnostic challenges that this entity presents, and to review staining patterns which may be useful in its diagnosis.

Male Breast Cancer (MBC) - A Review.

Males account for 1% of all cases of breast cancer. With the aging of the world's population, the disease has exhibited a rise in incidence in recent decades. Male breasts are smaller than female breasts, making the disease easier to spot, but patients often do not report their cases in time due to a lack of awareness. The stage-to-stage prognosis of male breast cancer is comparable to that of their female counterparts. Due to the relative rarity of the disease and poor patient enrollment in large randomized studies, the optimal management of male breast cancer remains uncertain. This article presents a narrative review of male breast cancer in light of recent literature, with an emphasis on epidemiology, clinical features, and current management.

Clinical, Pathological, and Prognostic Features of Male Breast Cancer: A Multicenter Study.

Male breast cancer (BC) represents less than 1% of male tumors. Little is known about male BC characteristics, management, and survival, with many studies based on a small number of cases. Consequently, the treatment of male BC lacks specific guidelines. The aims of the study are to compare male and female breast cancer (FBC) in terms of cancer clinical and anatomopathological features and treatment approach, and to identify differences between male BC and FBC in terms of survival. Patients and methods: Data from 2006 to 2018 were retrospectively acquired. Amounts of 49 males and 680 postmenopausal females with primary non-metastatic BC who underwent breast surgery at Mauriziano Hospital or IRCCS Candiolo (TO-Italy) were included. The mean age at diagnosis for male BC was 68.6 years, and males presented a smaller tumor size than women (p < 0.05) at diagnosis. Most male BC patients received adjuvant endocrine therapy (AET) with tamoxifen (73.5%). AET drop-out rate due to side effects was 16.3% for males compared to 7.6% for women (p = 0.04). Comparing FBC and male BC, no differences have been identified in terms of DFS and OS, with a similar 10-year-relapse rate (12% male BC vs. 12.4% FBC). Propensity Score Matching by age, nodal status, pT, and molecular subtype had been performed and no differences in OS and DFS were seen between male BC and FBC. In conclusion, male BC and FBC have similar prognostic factors and survival outcomes. The drop-out rate of AET was higher in males, and side effects were the main reason for drug discontinuation.

Male Breast Cancer: Three Case Reports and a Literature Review.

INTRODUCTION: Male breast cancer (MBC) accounts for 0.5%-1% of all breast cancers diagnosed worldwide. However, its biological characteristics can be distinguished from that of female breast cancer (FBC). CASE REPRESENTATION: The diagnostic and treatment approaches for MBC are mainly similar to that of FBC due to the lack of male breast cancer-related studies, clinical trials, and literature. An increasing number of retrospective and prospective studies have been conducted to clarify the individualized care for MBC. Herein, we report three cases of advanced MBC to describe the diagnostic approaches, treatment process, and survival prognosis. CONCLUSION: MBC patients had older age, later stage at first diagnosis, higher expression of hormone receptors, and poor prognosis. A literature review was conducted to determine the incidence, risk factors, disease features, diagnosis, treatment, survival, and management of MBC.

Mammary not otherwise specified-type sarcoma with CD10 expression.

Although mammary carcinoma is one of the most common malignancies among women, sarcoma taking origin from the breast tissue is extremely rare. Most of the mammary sarcomas represent a specific entity such as malignant phyllodes tumor, liposarcoma, or angiosarcoma. However, some cases do not fit into any specific category of sarcoma. These cases are diagnosed with breast sarcoma-not otherwise specified (NOS) type. They constantly express CD10 and are called as NOS type sarcoma with CD10 expression. Herein, we report a case of primary mammary sarcoma-NOS type with CD10 expression in an 80-year-old male. It was misdiagnosed with carcinoma breast on fine-needle aspiration. However, on histology, it was a high-grade tumor without any specific differentiation. Immunohistochemical results showed diffuse strong expression of vimentin and CD10, whereas pancytokeratin, desmin, and CD34 were negative. These tumors are considered a variant of sarcoma with myoepithelial differentiation.

The prediction of distant metastasis risk for male breast cancer patients based on an interpretable machine learning model.

OBJECTIVES: This research was designed to compare the ability of different machine learning (ML) models and nomogram to predict distant metastasis in male breast cancer (MBC) patients and to interpret the optimal ML model by SHapley Additive exPlanations (SHAP) framework. METHODS: Four powerful ML models were developed using data from male breast cancer (MBC) patients in the SEER database between 2010 and 2015 and MBC patients from our hospital between 2010 and 2020. The area under curve (AUC) and Brier score were used to assess the capacity of different models. The Delong test was applied to compare the performance of the models. Univariable and multivariable analysis were conducted using logistic regression. RESULTS: Of 2351 patients were analyzed; 168 (7.1%) had distant metastasis (M1); 117 (5.0%) had bone metastasis, and 71 (3.0%) had lung metastasis. The median age at diagnosis is 68.0 years old. Most patients did not receive radiotherapy (1723, 73.3%) or chemotherapy (1447, 61.5%). The XGB model was the best ML model for predicting M1 in MBC patients. It showed the largest AUC value in the tenfold cross validation (AUC:0.884; SD:0.02), training (AUC:0.907; 95% CI: 0.899-0.917), testing (AUC:0.827; 95% CI: 0.802-0.857) and external validation (AUC:0.754; 95% CI: 0.739-0.771) sets. It also showed powerful ability in the prediction of bone metastasis (AUC: 0.880, 95% CI: 0.856-0.903 in the training set; AUC: 0.823, 95% CI:0.790-0.848 in the test set; AUC: 0.747, 95% CI: 0.727-0.764 in the external validation set) and lung metastasis (AUC: 0.906, 95% CI: 0.877-0.928 in training set; AUC: 0.859, 95% CI: 0.816-0.891 in the test set; AUC: 0.756, 95% CI: 0.732-0.777 in the external validation set). The AUC value of the XGB model was larger than that of nomogram in the training (0.907 vs 0.802) and external validation (0.754 vs 0.706) sets. CONCLUSIONS: The XGB model is a better predictor of distant metastasis among MBC patients than other ML models and nomogram; furthermore, the XGB model is a powerful model for predicting bone and lung metastasis. Combining with SHAP values, it could help doctors intuitively understand the impact of each variable on outcome.

[Breast cancer in men]. / Mammakarzinom beim Mann.

Male breast cancer is an unknown field for many practitioners. Patients often see different doctors before the correct diagnosis is made - often too late. This article is intended to point out risk factors, initiation of diagnostics and therapy. In the dawning age of molecular medicine, we will also take a look at genetics.

A Rare Case of Invasive Cribriform Carcinoma in Male Breast.

BACKGROUND Male breast cancer is a very rare disease that represents 0.6% of all breast carcinomas. Among breast carcinomas, invasive cribriform carcinoma (ICC) is a rare type of breast carcinoma and is more common in older women, with only a few cases in men reported. We present a case of male breast cancer with ICC. CASE REPORT A 58-year-old man presented with a painful and palpable mass in the left breast, which was diagnosed as breast cancer of the ICC type. The patient underwent total mastectomy plus sentinel lymph node biopsy. On the microscope, the tumor was composed of more than 90% cribriform glands with comedo necrosis and dystrophic calcification. On immunohistochemical (IHC) staining, it appeared to be a luminal breast cancer. The IHC staining for c-erb B2 was equivocal (2 positive); hence fluorescence in situ hybridization was performed, and showed no amplification of the HER2/neu oncogene. The Ki-67 labeling index was 30%. The patient received radiotherapy and adjuvant systemic chemotherapy (4 cycles of docetaxel and cyclophosphamide), and has been on antiestrogen therapy (daily tamoxifen, 20 mg) for 30 months with no evidence of disease. CONCLUSIONS ICC is a rare type of invasive carcinoma of the breast, and ICC from the male breast is extremely rare. We report, in this case, the final pathologic results of a male patient diagnosed with ICC breast cancer and treated with surgery, chemotherapy, and radiotherapy.

Discussion and Optimization of the Male Breast Cancer Patient Experience.

Breast cancer in men is rare and often overlooked as there is a misconception that it is a gendered disease that affects women only. The feminization, or "pinkification," of the disease has been socially constructed to raise awareness, improve screening, and empower women but has not addressed the occurrence of the illness in men. Men may therefore experience unique psychosocial difficulties when faced with a disease that predominantly affects women, including feelings of disbelief and embarrassment that impact their sense of self and challenge their masculinity. The lack of mammographic screening in men, lack of public awareness, and the shame that develops during the time of diagnosis can result in treatment avoidant behaviors, a delayed presentation, and worse prognosis in men. Although male breast cancer (MBC) is uncommon, the incidence is increasing; therefore, efforts should be made to enhance education for health care professionals and the general public in order to lessen the stigma, with the goal of improving outcomes. Furthermore, special attention to the unique medical needs and hurdles encountered by transgender males can break down health care barriers in this marginalized patient population. This article offers male perceptions on breast cancer, the psychosocial implications of being diagnosed with a gendered disease, and suggestions on how to improve the MBC experience.

Breast Cancer Screening in Men.

Breast cancer screening has been highly successful in women in reducing mortality through early detection. In comparison, clinical detection of breast cancer remains the norm in men, and delay in diagnosis is reflected by a persistent survival disparity compared to women despite advances in modern therapy. Male breast cancer presents an interesting dilemma. While mammography is highly sensitive and specific for male breast cancer, routine screening is not justified by the overall low disease incidence. Yet there has been interest in leveraging mammography in targeted screening of men with identifiable risk factors to allow early detection, and early data may support this approach. The purpose of this article is to explore the potential utility of targeted breast cancer screening in men by examining unique clinical and biologic characteristics of male breast cancers that may lend themselves to mammographic detection. We will also discuss available evidence in screening outcomes in men and summarize recent updates in risk management recommendations in Society guidelines.

[Malignant Melanoma of a Male Breast That Was Difficult to Differentiate from Breast Cancer-A Case Report].

INTRODUCTION: Malignant melanoma in the male breast is extremely rare. Here we report a case of malignant melanoma in which a small cystic lesion in the male breast gradually increased during follow-up and was difficult to distinguish from breast cancer. CASE: A 65-year-old male was diagnosed with a tumor in the right breast and was referred to our department for further examination. At 42 years of age, he underwent tumor resection of a malignant melanoma of the abdominal skin. Mammary ultrasonography showed a 0.6 cm cystic mass in his right breast. Eight months later, the right breast mass had increased to 1.4 cm, and a core needle biopsy suggested breast cancer. Total mastectomy with axillary lymph node dissection was performed. HE staining of the resected tumor showed intranuclear inclusion bodies and some large nucleoli. On the basis of various immunostaining methods, malignant melanoma was diagnosed instead of breast cancer. After surgery, adjuvant chemotherapy with molecularly targeted drugs was administered. DISCUSSION: This might have been a case of male breast metastasis of malignant melanoma with very late recurrence.

Risk stratification system and visualized dynamic nomogram constructed for predicting diagnosis and prognosis in rare male breast cancer patients with bone metastases.

Background: Bone metastases (BM) from malignant tumors could disrupt the balance between osteoclasts and osteoblasts and affect bone homeostasis. Malignant breast cancer (BC) is rare in male patients, and co-occurrence of BM is even rarer. Given its low incidence, there is limited research evaluating risk and prognosis. Despite the widespread application of nomograms to predict uncommon malignancies, no studies have constructed predictive models focusing on the diagnosis and prognosis of male breast cancer with bone metastases (MBCBM). Methods: This study selected all male breast cancer patients (MBC) between 2010 and 2019 in the Surveillance, Epidemiology, and End Results (SEER) database. We used simple and multivariate Logistic regression analyses to identify independent risk factors for BM in MBC patients. Then simple and multivariate Cox regression analyses were employed to determine the independent prognostic factors for overall survival (OS) and cancer-specific survival (CSS) in MBCBM patients. We established and validated three new nomograms based on these independent factors. Result: A total of 4187 MBC patients were included, with 191 (4.56%) having bone metastases at the time of diagnosis. The independent risk factors of BM in MBC patients included age, tumor size, marital status, T stage, and N stage. In MBCBM patients, independent prognostic factors for OS and CSS were both age, T stage, ER status, PR status, and surgery. The concordance index (C-index), the area under the curve (AUC) of the receiver operating characteristic curve (ROC), the calibration curve, and the decision curve analysis (DCA) confirmed that these three nomograms could accurately predict the diagnosis and prognosis of MBCBM patients with excellent discrimination and clinical utility superior to the TNM staging system. We then established two prognostic-based risk stratification systems and three visualized dynamic nomograms that could be applied in clinical practice. Conclusion: In conclusion, this study aimed to establish and validate an accurate novel nomogram to objectively predict the diagnosis and prognosis of MBCBM patients. On this basis, prognostic-based risk stratification systems and visualized dynamic nomograms were constructed to facilitate doctors and patients to quantify individual BM risk probability and survival probability to assist in personalized risk assessment and clinical decision-making.

Health education actions on male breast cancer: A protocol for systematic review and meta analysis.

BACKGROUND: Although rare, the rates of diagnosis of male breast cancer (MBC) have been increasing over the years, and it can be quite aggressive in the male organism. Some strategies such as health education disseminating knowledge about MBC can be essential for early discovery and finding better prognosis. OBJECTIVE: Protocol to map the available evidence of health education approaches on MBC. METHODS: A scoping review on health education on MBC will be carried out in Latin American and Caribbean Literature on Health Sciences (LILACS), Web of Science, Scopus, Scielo, Online System of Literature Search and Analysis Medical (MEDLINE), Embase, Virtual Health Library (VHL). Two independent reviewers will perform screening, data extraction, and risk of bias assessment through the Joanna Briggs Institute (JBI) Critical Assessment Checklist. For the quality of evidence, the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) Analysis will be used. RESULTS: The results of this review will be published in a peer-reviewed journal. CONCLUSIONS: This scoping review will provide evidence of how health education on MBC is being addressed in health systems. Evidence can help healthcare professionals and patients recognize the most effective educational inventions in disseminating knowledge and preventing MBC.

Sweat Gland Carcinoma With Neuroendocrine Differentiation of the Areola as a Potential Clinicopathologic Mimicker of Male Breast Carcinoma and Syringocystadenocarcinoma Papilliferum.

ABSTRACT: Sweat gland carcinoma with neuroendocrine differentiation (SCAND) is a newly proposed tumor entity of primary cutaneous apocrine/eccrine adnexal tumor with neuroendocrine differentiation. The histopathologic variations are not yet well known. In this article, we present a case of SCAND mimicking male breast cancer and syringocystadenocarcinoma papilliferum. A 68-year-old man presented with a reddish 12-mm nodule on his left areola. No lymph node or distant metastases were observed. The patient was disease free 1 year and 9 months after the tumor was surgically resected but died of cerebral hemorrhage. Histopathological examination revealed a predominantly intradermal tumor with marked syringotropism, mimicking a component of mammary ductal carcinoma in situ. In addition, another tissue section displayed a cup-shaped papillated tumor with syringocystadenocarcinoma papilliferum-like features, which were also seen because of marked syringotropism. Diffuse immunoexpression of cytokeratin 7, cytokeratin 19, chromogranin A, synaptophysin, INSM1, estrogen receptor, carcinoembryonic antigen, epithelial membrane antigen, and GATA3 was observed in the tumor, but no BRAF immunoexpression was seen. The present case would help us to understand the histopathological variation and differential diagnosis of SCAND. The histopathological diagnosis of male breast cancer or syringocystadenocarcinoma papilliferum should be made by ruling out SCAND.

Carcinoma male breast with tracheal and endobronchial metastasis, masquerading as nonsmall-cell lung cancer, presenting with superior vena cava obstruction - A rare case report.

Cancer male breast is not very common. It comprises <1% of all breast cancers. Primary sites of metastasis are bone, brain, lung, and liver. Endobronchial and tracheal metastasis is very rare. To the best of our information, this is the first case of male breast carcinoma with upfront tracheal and endobronchial metastasis which presented as Superior vena cava obstruction (SVCO), initially evaluated on the lines of metastatic nonsmall-cell lung cancer. A 60-year-old gentleman presented with shortness of breath and features of SVCO. On primary evaluation, he was thought to be a case of nonsmall-cell lung cancer. Later on, it was confirmed to be carcinoma male breast with endobronchial and tracheal metastasis, which was reconfirmed with biopsy. The case we came across had symptoms associated with endobronchial metastases from primary extrapulmonary tumor and which was later found out to be breast. Treatment options are very different from lung primary and thus, we should be aware of the unusual disease presentation.

Clinicopathological features of male patients with breast cancer based on a nationwide registry database in Japan.

BACKGROUND: Male breast cancer (MBC) is rare; however, its incidence is increasing. There have been no large-scale reports on the clinicopathological characteristics of MBC in Japan. METHODS: We investigated patients diagnosed with breast cancer in the Japanese National Clinical Database (NCD) between January 2012 and December 2018. RESULTS: A total of 594,316 cases of breast cancer, including 3780 MBC (0.6%) and 590,536 female breast cancer (FBC) (99.4%), were evaluated. The median age at MBC and FBC diagnosis was 71 (45-86, 5-95%) and 60 years (39-83) (p < 0.001), respectively. MBC cases had a higher clinical stage than FBC cases: 7.4 vs. 13.3% stage 0, 37.2 vs. 44.3% stage I, 25.6 vs. 23.9% stage IIA, 8.8 vs. 8.4% stage IIB, 1.9 vs. 2.4% stage IIIA, 10.1 vs. 3.3% stage IIIB, and 1.1 vs. 1.3% stage IIIC (p < 0.001). Breast-conserving surgery was more frequent in FBC (14.6 vs. 46.7%, p = 0.02). Axillary lymph node dissection was more frequent in MBC cases (32.9 vs. 25.2%, p < 0.001). Estrogen receptor(ER)-positive disease was observed in 95.6% of MBC and 85.3% of FBC cases (p < 0.001). The HER2-positive disease rates were 9.5% and 15.7%, respectively (p < 0.001). Comorbidities were more frequent in MBC (57.3 vs. 32.8%) (p < 0.001). Chemotherapy was less common in MBC, while endocrine therapy use was similar in ER-positive MBC and FBC. Perioperative radiation therapy was performed in 14.3% and 44.3% of cases. CONCLUSION: Japanese MBC had an older age of onset, were more likely to be hormone receptor-positive disease, and received less perioperative chemotherapy than FBC.