Contralateral Axillary Lymph Node Metastasis Research Articles

Survival After Contralateral Axillary Metastasis in Breast Cancer.

Despite stage IV categorization, survival outcomes for breast cancer patients who experience contralateral axillary lymph node metastasis (CAM) remain uncertain. This study aimed to investigate the clinical outcomes for patients with metachronous CAM to provide insights into its prognosis and treatment recommendations. This study retrospectively reviewed medical records of patients who underwent curative surgery for breast cancer and experienced CAM as the first site of distant metastasis (DM) during the follow-up period between January 2001 and April 2023. Survival outcomes of the CAM patients were compared with those of breast cancer patients with other DM via propensity score-matching (PSM). The study identified 40 breast cancer patients with metachronous CAM. The estimated 5-year overall survival (OS) was 39.6%, and the progression-free survival was 39.4%. The patients with CAM exhibited marginally better OS than the patients with DM (p = 0.071), but survival similar to that of the patients with isolated supraclavicular node recurrence (SCN) (p = 0.509). Moreover, matching of CAM with DM using two PSM models showed a consistently insignificant survival difference (hazard ratio [HR], 1.47; p = 0.124 vs. HR, 1.19; p = 0.542). Ipsilateral breast tumor recurrences (IBTRs) were experienced by 12 patients before or concurrently with the CAM. These patients exhibited significantly better survival than the remaining patients (HR, 0.28; p = 0.024). The breast cancer patients with CAM showed survival similar to that for the patients with DM, supporting the current stage IV classification of the CAM. However, CAM associated with IBTR exhibited superior survival outcomes, suggesting that this subset of CAM may benefit from treatments with curative intent.

Contralateral axillary lymph node metastasis of breast cancer: UK single-centre 10-year experience

Contralateral axillary lymph node metastasis of breast cancer: UK single-centre 10-year experience

Surgery on Metastatic Foci is a Better Strategy for Stage IV Breast Cancer Patients with only Nonregional Lymph Node Metastasis.

Our study aims to explore whether breast cancer patients with non-regional lymph node (NRLN) metastasis benefit from surgery on distant nodes, and to determine the influencing factors affecting the prognosis of this type of patient. Information of invasive ductal carcinoma (IDC) patients from 2004 to 2016 was extracted from the Surveillance, Epidemiology, and End Results (SEER) database and analyzed by statistical methods, including multivariate Cox regression model, chi-squared test, propensity score matching (PSM), Kaplan-Meier plot, and log-rank test. A total of 4236 M1 patients met the designated criteria. Among 847 patients with only NRLN metastasis who have detailed information, only 114 patients received surgery on metastatic distant lymph nodes. The Kaplan-Meier plot for overall survival (OS) showed that the prognosis of NRLN metastatic patients was superior to visceral metastasis (P<0.0001) but similar to supraclavicular metastasis (P=0.33). In addition, NRLN metastatic patients who underwent surgery on the NRLNs were found to have superior prognoses in terms of both OS (P=0.041) and cancer-specific survival (P=0.034) compared with those who did not undergo NRLN surgery. We have also demonstrated that NRLN metastatic patients who have received radiotherapy plus chemotherapy for primary tumors gain superior survival compared with those who only received chemotherapy apart from NRLN surgery. Surgery on NRLN and radiotherapy for the primary tumor improved the prognosis of NRLN metastatic patients. Thus, the classification of NRLN, especially contralateral axillary lymph node metastasis (CAM), into the M1 breast cancer stage should be reconsidered. Different locoregional treatment strategies for metastatic foci should be recommended for patients with only NRLN and patients with visceral metastasis.

Abstract P5-01-04: Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression?

Abstract Background: Contralateral axillary lymph node metastasis (CAM) in breast cancer is currently classified as a stage IV disease but its prognosis is still controversial. Purpose: To determine outcomes in overall survival (OS) and disease-free survival (DFS) in patients with and without locoregional tumor recurrence who present with contralateral axillary lymph node metastasis (CAM). Methods: Patients with pathologically confirmed invasive breast cancer with metachronous CAM who received treatment between 1988 and 2017 were retrospectively reviewed. Patients with other distant metastases at the time of CAM diagnosis were excluded. The outcome of CAM in cases of IBTR and regional recurrence (RR) were compared to CAM not accompanied by locoregional tumor recurrence. Results: Thirty-eight patients with metachronous CAM were included in the study. Metachronous CAM occurred 55 months (interquartile range, 17-77 months) after surgical treatment of the primary tumor and median follow-up was 95 months (interquartile range, 49-117 months) from the initial operation date and 40 months (interquartile range, 15-54 months) from the diagnosis of CAM. At the time of initial CAM diagnosis, 11 patients had IBTR, 12 patients had RR, and 15 patients had no locoregional recurrence. The estimated 5-year OS was 49.1% and 5-year DFS was 45.3%. Although statistically insignificant due to small sample size, when stratified by loco regional recurrence, the prognosis of CAM patients with IBTR appeared to be better than those without locoregional recurrence (5-year OS: 88.9% vs. 41.4%, HR 5.88, p = 0.09) whereas the prognosis of CAM patients with RR was worse than those without locoregional recurrence (5-year OS: 35.4% vs. 41.4%, HR 0.44, p = 0.20). Axillary lymph node dissection (ALND) improved median OS (83 vs. 36 months, p = 0.069) in all patients. When stratified, improvement in median OS was 13 vs 27 months (p = 0.094) in patients with RR, and 36 vs. 65 months (p = 0.061) in patients without locoregional recurrence. For patients accompanied by IBTR, ALND was performed in 8 out of 11 and only one patient died during the follow-up period. Conclusion: Our study indicates that the patients with CAM have superior survival outcome when compared to other stage IV patients, especially when CAM was accompanied by other loco regional recurrences. These data suggest that the CAM patients may benefit from active loco regional treatment. Citation Format: Ji-Jung Jung, Hyeong-Gon Moon, Wonshik Han, Han-Byoel Lee, Hong-Kyu Kim, Jung Whan Chun, Eunhye Kang, Changjin Lim, Jang-il Kim, Hyunsu Yeoh. Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression? [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-01-04.

Abstract P4-07-59: Management of Isolated Contralateral Axillary Lymph Node Metastasis in Breast Cancer: A Single Institution Experience

Abstract Background: Contralateral axillary lymph node metastasis (CAM) in breast cancer (BC) is uncommon with an incidence of 1.9-6%. It is considered as stage IV disease based on the TNM classification in the 8th edition of the American Joint Committee on Cancer (AJCC) staging manual. However, in the absence of other distant metastases, patients with CAM have been found to have better outcomes compared to those with stage IV disease. Recent studies suggest that CAM may represent locoregional spread of tumor through lymphatics rather than hematogenous spread and patients should be classified as N3 rather than M1. There are no clear guidelines on the optimal management of these patients and it is unclear if patients with isolated CAM should be treated as curative intent or as metastatic disease with palliative treatment. The goal of this study was to describe the management and outcomes of patients with BC and isolated CAM seen at our institution. Methods: We performed a retrospective chart review on all patients with BC and isolated CAM but no other distant metastases who were seen at our institution between 2000-2021. We collected information on demographics, tumor characteristics, intent of therapy (curative versus palliative), types of treatment (systemic treatments including chemotherapy (CT), hormone therapy, targeted therapy; radiation therapy; surgery), and response to frontline treatment. Results: We identified a total of ten eligible patients who were diagnosed between 2011-2020. The median age of diagnosis was 57 years and 70% had de novo cancers while the remainder had recurrent disease. The table below describes each patient’s cancer, treatment, and response. Patients are listed in chronological order, with those at the top diagnosed in 2011 and bottom in 2020. Four patients had hormone receptor (HR)-positive and HER2-negative BC, 3 patients had triple negative BC, 2 had HER2-positive BC and 1 had HR-positive and HER2-positive BC. Regarding treatment, 50% of patients were treated with curative intent, of whom 3 have no evidence of recurrence at a follow up of 23-137 months. Of the other two patients, one had response to systemic treatment but remains surgically unresectable and the other patient developed recurrent disease. In the 5 patients treated with palliative systemic therapy as Stage IV disease, 3 patients had clinical response to first line treatment with control of disease. One patient who passed away had triple negative disease. The last patient developed progression of disease and is on second line systemic treatment. Conclusions: At our institution, among patients treated with palliative intent systemic therapy, most (60%) had a response to first line treatment. In the 5 patients treated with curative intent, 3 patients remain without evidence of recurrence of whom 2 have had 9 years of follow up. The current study illustrates the heterogeneity in management for patients with CAM. Our findings highlight the need for larger studies focusing on BC patients with CAM to optimize their treatment and outcomes. Limitations of our study include its retrospective nature and small sample size given rarity of CAM. Table 1. Treatment and Outcomes of Patients with CAM Citation Format: Rima Patel, Shana Berwick, Cao Jin, Paula Klein. Management of Isolated Contralateral Axillary Lymph Node Metastasis in Breast Cancer: A Single Institution Experience [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-59.

Contralateral Axillary Lymph Node Metastasis of Breast Cancer: Retrospective Analysis and Literature Review.

BackgroundContralateral axillary lymph node metastasis (CAM) is classified as distant metastasis in guidelines, but the prognosis is better than that of stage IV patients. It is controversial to classify CAM as a distant metastasis or a regional metastasis, and the optimal treatment strategy for CAM is unknown.Patients and MethodsBreast cancer patients who were confirmed by pathology and treated at Shandong Cancer Hospital between January 2012 and July 2021 were included in our study. We retrospectively reviewed the medical records of the patients for their clinical features, pathological diagnosis, treatment strategy, and follow-up data. Survival analysis was calculated by Kaplan–Meier analysis, and patient matching was performed by case–control matching.ResultsA total of 60 patients were included, and there were 49 metachronous CAM cases and 11 synchronous CAM cases. The prognosis of isolated CAM patients was better than that of patients with other distant metastases in terms of CAM-OS and PFS with significant differences (median CAM-OS 71.0 vs. 30.0 months, P=0.022; median PFS 42.0 vs. 11.0 months, P=0.009) and OS without significant differences (median OS 126.0 vs. 79.0 months, P=0.111). The five-year survival rate of isolated CAM patients was 67.4%, and the five-year disease-free survival (DFS) rate was 52.9%. The prognosis of CAM patients was similar to that of N3M0 patients in terms of OS (mean OS 82.4 vs. 65.6 months, P=0.537) and DFS (mean PFS 54.5 vs. 52.6 months, P=0.888). Axillary lymph node dissection (ALND) or low-middle level ALND significantly improved the OS (mean OS 237.4 vs. 111.0 months, P=0.011), CAM-OS (mean CAM-OS 105.2 vs. 46.6 months, P = 0.002), and PFS (mean PFS 92.3 vs. 26.9 months, P = 0.001) of isolated CAM patients. Axillary radiotherapy improved PFS, CAM-OS, and OS but without significant differences (mean PFS 80.0 vs. 46.6 months, P = 0.345; mean CAM-OS 86.8 vs. 72.1 months, P = 0.338; mean OS 147.6 vs. 133.0 months, P = 0.426).ConclusionCAM should be diagnosed as local recurrence and treated with aggressive and curative rather than palliative strategies. Contralateral axillary surgery and radiotherapy are recommended for isolated CAM patients.

Contralateral axillary lymph node metastasis in primary breast cancer: A case report.

IntroductionContralateral axillary lymph node metastasis (CAM) is rare, especially in primary breast cancer.Presentation of caseA 71-year-old woman visited our hospital after noticing a mass in her right breast. A mass of 5 cm in diameter with skin infiltration was palpable on the medial side of the right breast. She underwent a needle biopsy and was diagnosed with invasive ductal carcinoma. On various imaging modalities, there were no distant metastases but bilateral axillary lymph node metastases were found. She underwent preoperative chemotherapy and showed a clinical partial response. After thorough discussion, she opted for surgery and underwent partial mastectomy of the right breast and bilateral axillary lymph node dissection. Histopathological examination revealed residual breast tumor and one metastatic axillary lymph node on each side. Postoperative radiotherapy and hormone therapy were performed. The patient is alive and recurrence-free as of 1 year after the start of treatment.ConclusionCAM is often regarded as distant metastasis, but can be considered curable if there is no distant metastasis to other organs. CAM without distant metastasis to other organs should be treated with curative intent in order to avoid a disadvantage to the patient.

Breast cancer metastasizing to the contralateral axilla several years after treatment: A case report with literature review.

Introduction and importanceLymph node metastasis is the most prominent prognostic factor in breast cancer. The aim of this paper is to report a case of contralateral axillary lymph node metastasis (CAM) which look like metachronous initially, but histopathologicaly confirmed as synchronous CAM.Case presentationA-44-year old female was a known case of left breast cancer five years prior to this presentation (T2,N2,M0, grade III, Triple negative, multifocal invasive ductal carcinoma). On follow up, multiple contralateral axillary suspicious lymph nodes were discovered. Fine Needle Aspiration Cytology from the lesion revealed grade III, Triple negative, invasive ductal carcinoma consistent with metastasis from the left invasive ductal carcinoma. Bilateral mastectomy and right axillary dissection were performed. The histopathological examination and immunohistochemistry showed left breast recurrent 0.5 cm grade III, Triple negative invasive ductal carcinoma.DiscussionIf a cancer is found in the contralateral axilla, three main potential sources should be considered: contralateral spread from the original breast tumor, metastasis from an occult primary in the ipsilateral breast, and metastasis from an extramammary site.ConclusionAlthough CAM in patients with breast cancer is an uncommon condition, it is still possible to occur. There is a controversy regarding the appropriate management.

Contralateral axillary lymph node metastasis and molecular changes in second primary breast cancer: a case report

: Contralateral axillary metastasis (CAM) is rather rare in primary breast cancer. In this case, we present a 46-year-old female patient who underwent left breast-conserving surgery (BCS) and left axillary lymph node dissection (ALND). Two years later, an enlarged lymph node was found in her right axilla. Magnetic resonance imaging (MRI) of the breast displayed a left breast mass with multiple internal mammary lymph nodes and abnormal lymph nodes in the right axillary region. However, no abnormalities were found in the right breast. The left breast mass was diagnosed as invasive carcinoma by core needle biopsy. During the operation, we suggested that the contralateral lymph nodes were metastatic from the second primary breast cancer by preoperative 99mTc injection around the left breast. The patient underwent left mastectomy and right axillary lymph node dissection. The postoperative pathology was diagnosed as metachronous secondary primary left breast cancer, in which the initial presentation was lymph node metastasis to the contralateral axilla of the left breast. Therefore, we propose that CAM may be more common in second primary or recurrent breast cancer. It should be treated as locoregional extension. Preoperative lymph node markers are important to identify whether contralateral axillary lymph node metastasis occurs from a second primary breast cancer.

Ipsilateral Breast Tumor Recurrence with Metachronous Contralateral Axillary Lymph Node Metastasis after Breast-Conserving Surgery with Axillary Lymph Node Dissection

Ipsilateral Breast Tumor Recurrence with Metachronous Contralateral Axillary Lymph Node Metastasis after Breast-Conserving Surgery with Axillary Lymph Node Dissection

Contralateral Axillary Lymph Node Metastases from Breast Carcinoma: Is it Time to Review TNM Cancer Staging?

Contralateral axillary lymph node metastasis (CAM) is an infrequent clinical condition currently considered an M1, stage IV, disease. Due to the absence of shared data on CAM significance and on its therapeutic approach, be it curative or simply palliative, its management is still uncertain and undoubtedly represents a clinical challenge. Patients with pathologically confirmed metachronous CAM were retrospectively evaluated. All patients had been managed at the European Institute of Oncology, Milan, Italy, from 1997. Patients with distant metastases at the time of CAM were excluded. Possible treatments included surgery, systemic therapy and RT (radiotherapy). Outcomes were evaluated as rates of disease-free survival (DFS) and of overall survival (OS). Forty-seven patients with CAM were included in the study. Metachronous CAM occurred 73months (range 5-500months) after diagnosis of the primary tumor. The median follow-up time was 5.4years (interquartile range 2.9-7.0years). The estimated OS was 72% at 5years (95% CI 54-83), and 61% at 8years (95% CI 43-75). The estimated DFS was 61% at 5years (95% CI 44-74), and 42% at 8years (95% CI 25-59). These findings, together with those from previous studies, show that CAM outcome, particularly if measured as OS, appear better than at other sites of distant dissemination, when CAM is subjected to surgical and systemic treatments with a curative intent. Therefore, a new clinical scenario is suggested where, in the TNM system, CAM is no longer classified as a stage IV, but as an N3 disease.

ASO Author Reflections: Future View: A Recent Scientific Contribution Towards a Staging Revision of Contralateral Axillary Lymph Node Metastases from Breast Cancer.

ASO Author Reflections: Future View: A Recent Scientific Contribution Towards a Staging Revision of Contralateral Axillary Lymph Node Metastases from Breast Cancer.

TREATMENT OF BREAST CANCER WITH METASTATIC CONTRALATERAL AXILLARY LYMPH NODES: CASE REPORT AND LITERATURE REVIEW

Background . until now, only a few reports have been available on clinical management of breast cancer patients with metastases to the contralateral axillary lymph nodes. Breast cancer is traditionally considered to affect ipsilateral lymph nodes. However, there are many reports describing cases with contralateral axillary lymph node metastasis. Case presentation . We report a case of cancer in the right breast with contralateral axillary lymph node metastasis (Т2N1М1). Histological examination revealed invasive ductal G2 carcinoma with angiolymphatic invasion. No mutations in the BRca1, BRca2, cHEK2, and NBs1 genes were detected. the patient received complex treatment. Literature review. a PubMed search was conducted using the systematic review filter to identify articles describing cases with contralateral axillary lymph node metastasis. contralateral axillary lymph node metastasis, especially after surgery or radiotherapy, should be considered not only as hematogeneous metastasis but also as lymphagenous metastasis. survival of these patients is more comparable to that observed in patients with locally-advanced cancer than to that observed in patients with distant metastases. Conclusion . Early detection and management of contralateral axillary lymph node metastasis in breast cancer patients remains a debatable topic. Factors affecting disease prognosis have not been identified yet. Further studies concerning staging of contralateral axillary lymph node metastasis are needed.

A Case of Local Recurrence of Breast Cancer with Contralateral Axillary Lymph Node Metastasis after Surgery for Paget's Disease of the Breast

A Case of Local Recurrence of Breast Cancer with Contralateral Axillary Lymph Node Metastasis after Surgery for Paget's Disease of the Breast

A Case of Breast Cancer with Contralateral Axillary Lymph Node Metastasis after Breast Conserving Surgery with Axillary Lymph Node Dissection

A Case of Breast Cancer with Contralateral Axillary Lymph Node Metastasis after Breast Conserving Surgery with Axillary Lymph Node Dissection

Management of contralateral axillary lymph node metastasis from breast cancer: a clinical dilemma.

Contralateral axillary lymph node metastasis (CAM) in breast cancer patients is uncommon and the source uncertain. Management is complicated when CAM occurs as the first event of relapse after treatment of the primary tumor, especially in the absence of metastatic disease elsewhere. We reviewed the records of all breast cancer patients treated during 1999-2012. All patients with pathologically confirmed metachronous CAM were included. The examined data were demographic characteristics, tumor features and management modalities. Data from an epidemiological report that described the pathological characteristics of breast cancer in China during 1999-2008 were employed to allow further comparison. Twenty-eight patients with CAM were included in the study; they comprised 0.81% of the total number of patients. The median patient age was 47 years (range, 27-60 years). Half of the initial breast cancers were located at inner and central sites. Initial cancers were generally locally advanced (stage III, 50%) and hormone receptor negative. Treatment modalities included axillary lymph node dissection (ALND), mastectomy, radiation, and chemotherapy (± targeted therapy). After 29 months of follow-up, 25 patients had disease progression with a median progression-free survival of 10 months. Regional recurrence was most commonly seen at sites including bilateral breast, chest wall and superficial lymph nodes, accounting for 44% (n = 11) of patients who progressed. Median progression-free survival was prolonged in patients treated with radiotherapy (10 months vs 22 months). During the observation period, 13 patients died of disease progression. We found that CAM was associated with tumors with aggressive pathological features and had a poor prognosis. CAM is most likely to be distant metastasis from the initial breast cancer through lymphatic drainage rather than regional metastasis from a new occult breast cancer. Comprehensive treatment including chemotherapy and radiotherapy can provide better control; however, ANLD alone is insufficient treatment and mastectomy is not recommended.

セカンドセンチネル生検にて対側腋窩転移を診断した乳房内再発乳癌の1例

セカンドセンチネル生検にて対側腋窩転移を診断した乳房内再発乳癌の1例

Metástasis ganglionares axilares contalaterales en cáncer de mama: controversia sobre su vía de diseminación, manejo y pronóstico

Contralateral axillary lymph node metastases are a rare presentation in breast cancer. Although they are considered stage IV of the disease, it has been postulated that the spread of tumour cells to the contralateral axillary lymph nodes could occur through the lymph vessels and not through the bloodstream. We report the case of a 35-year-old woman who was diagnosed with a stage III invasive breast carcinoma and was treated with neoadjuvant chemotherapy, modified radical mastectomy, radiotherapy and hormone therapy.Seven months after the surgery, the disease progressed, showing contralateral axillary lymph node metastases with no evidence of any other distant disease. This is an unusual progression of breast cancer and thus its management is not standardized. We reviewed the literature to search for evidence on how to treat this very special clinical situation.

Gastrin-releasing Peptide Receptor Imaging in Breast Cancer Using the Receptor Antagonist 68Ga-RM2 And PET

Introduction: The gastrin-releasing peptide receptor (GRPR) is overexpressed in breast cancer. The present study evaluates GRPR imaging as a novel imaging modality in breast cancer by employing positron emission tomography (PET) and the GRPR antagonist 68Ga-RM2.Methods: Fifteen female patients with biopsy confirmed primary breast carcinoma (3 bilateral tumors; median clinical stage IIB) underwent 68Ga-RM2-PET/CT for pretreatment staging. In vivo tumor uptake of 68Ga-RM2 was correlated with estrogen (ER) and progesterone (PR) receptor expression, HER2/neu status and MIB-1 proliferation index in breast core biopsy specimens.Results: 13/18 tumors demonstrated strongly increased 68Ga-RM2 uptake compared to normal breast tissue (defined as PET-positive). All PET-positive primary tumors were ER- and PR-positive (13/13) in contrast to only 1/5 PET-negative tumors. Mean SUVMAX of ER-positive tumors was 10.6±6.0 compared to 2.3±1.0 in ER-negative tumors (p=0.016). In a multivariate analysis including ER, PR, HER2/neu and MIB-1, only ER expression predicted 68Ga-RM2 uptake (model: r2=0.55, p=0.025). Normal breast tissue showed inter- and intraindividually variable, moderate GRPR binding (SUVMAX 2.3±1.0), while physiological uptake of other organs was considerably less except pancreas. Of note, 68Ga-RM2-PET/CT detected internal mammary lymph nodes with high 68Ga-RM2 uptake (n=8), a contralateral axillary lymph node metastasis (verified by biopsy) and bone metastases (n=1; not detected by bone scan and CT).Conclusion: Our study demonstrates that 68Ga-RM2-PET/CT is a promising imaging method in ER-positive breast cancer. In vivo GRPR binding assessed by 68Ga-RM2-PET/CT correlated with ER expression in primary tumors of untreated patients.

Effectiveness of Breast MRI and (18)F-FDG PET/CT for the Preoperative Staging of Invasive Lobular Carcinoma versus Ductal Carcinoma.

PurposeWe evaluated the utility of magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) for the preoperative staging of invasive lobular carcinoma (ILC) of the breast and compared the results with those of invasive ductal carcinoma (IDC).MethodsThe study included pathologically proven 32 ILCs and 73 IDCs. We compared clinical and histopathological characteristics and the diagnostic performances of MRI and 18F-FDG PET/CT for the primary mass, additional ipsilateral and/or contralateral lesion(s), and axillary lymph node metastasis between the ILC and IDC groups.ResultsPrimary ILCs were greater in size, but demonstrated lower maximum standardized uptake values than IDCs. All primary masses were detected on MRI. The detection rate for ILCs (75.0%) was lower than that for IDCs (83.6%) on 18F-FDG PET/CT, but the difference was not significant. For additional ipsilateral lesion(s), the sensitivities and specificities of MRI were 87.5% and 58.3% for ILC and 100.0% and 66.7% for IDC, respectively; whereas the sensitivities and specificities of 18F-FDG PET/CT were 0% and 91.7% for ILC and 37.5% and 94.7% for IDC, respectively. The sensitivity of 18F-FDG PET/CT for ipsilateral lesion(s) was significantly lower in the ILC group than the IDC group. The sensitivity for ipsilateral lesion(s) was significantly higher with MRI; however, specificity was higher with 18F-FDG PET/CT in both tumor groups. There was no significant difference in the diagnostic performance for additional contralateral lesion(s) or axillary lymph node metastasis on MRI or 18F-FDG PET/CT for ILC versus IDC.ConclusionThe MRI and 18F-FDG PET/CT detection rates for the primary cancer do not differ between the ILC and IDC groups. Although 18F-FDG PET/CT demonstrates lower sensitivity for primary and additional ipsilateral lesions, it shows higher specificity for additional ipsilateral lesions, and could play a complementary role in the staging of ILC as well as IDC.