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Overexpression of human epidermal growth factor receptor 2 (HER2) in breast cancer is correlated with poor prognosis. HER2-targeting drugs have been successful to treat HER2-positive breast cancer. However, the acquisition of the drug resistance with long-term use is still recognized. Here we report the novel molecular targets to treat HER2-positive breast cancer. HER2 is a key driving forces to proliferate HER2-positive breast cancer cells. Unlike other HER family members (EGFR, HER3, HER4), it recognizes no ligands and forms heterodimers with each other member, leading to the transduction of various cellular signals. Especially, the activated EGFR transactivates HER2, and the phosphorylation of both EGFR and HER2 strongly drives cell proliferation. In this study, we found that the degradation of an endosomal small GTPase, RhoB, by the ubiquitin ligase complex cullin-3 (CUL3)/KCTD10 is essential for both EGFR and HER2 phosphorylation in HER2-positive breast cancer cells. Depletion of CUL3 or KCTD10 drastically reduced the phosphorylation of EGFR and HER2, as well as HER2-positive breast cancer cell proliferation. As mechanisms, we identified a RhoB-interacting scaffold protein and an EGFR phosphatase from human protein arrays prepared by the wheat cell-free protein synthesis system, a unique technology of Ehime University. In HER2-positive breast cancer cells, we showed that the scaffold protein interacts with the EGFR phosphatase at the plasma membrane, which leads to inactivation of the EGFR phosphatase and inhibits EGFR dephosphorylation. Upon CUL3- or KCTD10-knockdwon, accumulated RhoB interacts with the scaffold protein, resulting in the release of active EGFR phosphatase. Using the METABRIC database, we next found that low expression of RhoB mRNA and high expression of scaffold protein correlate with poor prognosis for HER2-positive breast cancer patients. Additionally, high expression of scaffold protein was associated with poor prognosis in immunohistochemistry of HER2-positive breast cancer tissues. These data suggest that high expression of scaffold protein enhances cell proliferative signaling in HER2-positive breast cancers. The inhibitors of the scaffold protein/EGFR phosphatase interaction would be new therapeutic agents for HER2-positive breast cancer cells through EGFR dephosphorylation mediated by activation of the EGFR phosphatase. Citation Format: Kanako Nishiyama, Masashi Maekawa, Akari Murakami, Kaho Utsunomiya, Kana Takemoto, Erina Kusakabe, Haruna Noda, Reina Aoki, Kana Taguchi, Michiko Yamashita, Tomoya Nakagita, Jun Nakayama, Mami Chosei, Takeshi Kiyoi, Yoshiaki Kamei, Hiroyuki Takeda, Yasutsugu Takada, Shigeki Higashiyama. A novel mechanism of phosphatase activation for EGFR by Cullin-3/KCTD10 ubiquitin E3 complex in HER2-positive breast cancer cells [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-10-02.

Background: Tumor-infiltrating lymphocytes (TILs) are a useful prognostic factor and predictive biomarker of neoadjuvant chemotherapy treatment response for breast cancer, especially in human epidermal growth factor receptor type 2 (HER2)-positive breast cancer and triple-negative breast cancer (TNBC). However, due to heterogeneity of TIL expression and distribution in the tissues, accurately predicting TIL expression, especially using limited core-needle biopsy specimens, is difficult. Therefore, an accurate and simple preoperative evaluation method is needed. We have reported that the TILs-ultrasonography (US) score determined by characteristic US findings has a predictive performance for lymphocyte-predominant breast cancer (LPBC). This study aimed to investigate whether the TILs-US score with added vascularity assessment has a better predictive performance for LPBC. Methods: This multicenter, retrospective study investigated the validation and scoring of the LPBC characteristic imaging findings and applied it for LPBC and non-LPBC prediction. A total of 100 patients with HER2-positive breast cancer (n = 59) and TNBC (n = 41) treated by curative surgery between January 2014 and December 2021 were evaluated. Stromal lymphocytes in surgical pathological specimens were evaluated; the cutoff value for predicting LPBC was defined as ≥50% stromal TILs. Preoperative US was examined for TIL indicators. The US images with characteristic TILs were scored for LPBC prediction. Univariate and multivariate logistic regression analyses were employed for each potential predictor variable of LPBC. Results: A total of 40 patients with ≥50% stromal TILs were defined as having LPBC. The examined characteristic US findings for predicting LPBC, shape (more lobulated), internal echo level (weaker), posterior echoes (stronger), and vascularity assessment (hypervascularity), were significantly associated with LPBC and used to assign the scoring for predicting LPBC. As previously reported, the TILs-US score ranged from 0–7 points based on three ultrasonic tissue characteristics: shape (round, oval, and polygonal or irregular, 0 points; lobulated, 1 point; and small lobulated, 2 points), internal echo level (high or equal, 0 points; low, 1 point; and extremely low, 2 points), and posterior echoes (shadowing or attenuating, 0 points; no change, 1 point; accentuated, 2 points; and extremely accentuated, 3 points). We further added vascularity assessment (avascular or hypovascular, 0 point; moderately vascular, 1 point; and hypervascular, 2 points) to this scoring system. Based on the receiver operating characteristics (ROC) curves (AUC [Area Under the Curve] 0.77), the score cutoff for predicting LPBC was 4 points for TILs-US score (sensitivity, 0.83; specificity, 0.55; and accuracy, 0.66). Multivariate logistic regression analysis revealed that cT (< T2), estrogen receptor (ER) negativity, and a TILs-US score of ≥4 points were significant LPBC predictors (odds ratio [OR] 3.60; p = 0.028; OR 8.68; p = 0.020; OR 5.99; p = 0.005). Conversely, based on the ROC curves (AUC 0.78), the score cutoff for predicting LPBC was 5 points after adding vascularity assessment (sensitivity, 0.93; specificity, 0.57; and accuracy, 0.71). Multivariate logistic regression analysis revealed that cT (< T2), ER negativity, and a TILs-US score adding vascularity assessment of ≥5 points were significant LPBC predictors (OR 5.12; p = 0.010; OR 10.3; p = 0.019; OR 20.1; p < 0.001). Conclusions: Including the vascularity assessment to the TILs-US score, which can be noninvasively obtained using US, is a more accurate preoperative predictor of LPBC. Vascularity assessment may be an auxiliary factor in predicting LPBC. Univariate and multivariate logistic analysis of significant clinicopathological factors predicting lymphocyte-predominant breast cancer. Citation Format: Yuri Kimura, Norio Masumoto, Sadako Akashi-Tanaka, Kayo Fukui, Midori Noma, Aya Nagata, Takashi Nakamura, Hiroaki Shima, Toshitaka Okuno, Akari Murakami, Yoshiaki Kamei, Shogo Nakano, Koji Arihiro. The TILs-US score adding vascularity assessment based on ultrasonography for predicting tumor-infiltrating lymphocytes in human epidermal growth factor receptor 2-positive and triple-negative breast cancer [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 P3-04-10.

Background Fibroadenomas (FAs) and phyllodes tumors (PTs) are major benign breast tumors. They are pathologically classified as fibroepithelial tumors, composed of a proliferation of both epithelial and stroma. Although the clinical management of PTs differs from FAs, distinction by core needle biopsy diagnoses is still challenging. Computer-aided diagnosis is playing a pivotal role in accurate and objective evaluation of medical images. This technology opens up a new route to a solution for diagnostic problems. Methods A combined technique of label-free imaging with multi-photon microscopy and artificial intelligence was applied to detect quantitative signatures that differentiate fibroepithelial lesions. Multi-photon excited autofluorescence and second harmonic generation (SHG) signals were detected in tissue sections. A pixel-wise semantic segmentation method using a deep learning framework was used to separate epithelial and stromal regions automatically. Quantitative signatures, the epithelial to stromal area ratio, and the collagen SHG signal strength were investigated for their ability to distinguish between FA and PT lesions. Results Multi-photon microscopy recordings of tissue sections revealed distinct morphology between the epithelia and stroma, and further indicated that stromal regions emit a strong SHG signal which derives from collagen fibrils. However, this signal strength differs between the lesions, suggesting differences of collagenous molecular composition between the two lesions. In order to investigate hypertrophy of the stroma and compare this to the epithelial areas, an image segmentation analysis with a pixel-wise semantic segmentation framework using a deep convolutional neural network was performed. The deep learning-based analysis showed accurate separation of epithelial and stromal regions. Further investigation was conducted to determine if scoring the epithelial to stromal area ratio could be a marker for differentiating fibroadenoma and phyllodes tissues; we determined that most samples can be clearly separated but some are difficult to separate by the signature. Further investigations on the collagen SHG signal strength within the stromal area revealed accurate classification of the breast tissue lesions. Conclusions Molecular and morphological changes detected through the assistance of computational and label-free multi-photon imaging techniques enabled us to propose quantitative signatures for epithelial and stromal alterations in breast tissues.

Background Metaplastic carcinoma of the breast consists of both invasive ductal carcinoma and metaplastic carcinoma. This rare subtype of cancer has a poor prognosis. The development of metaplastic breast cancer and relationship with BRCA1 are not well known. Here, we report a rare case of germline BRCA1 mutation-positive breast cancer with chondroid metaplasia. Case presentation A 39-year-old Japanese woman with a family history of breast cancer in her mother and ovarian cancer in her maternal grandmother consulted at our hospital with a left breast mass. Needle biopsy for the mass was performed, leading to a diagnosis of invasive breast cancer with chondroid metaplasia. We performed left mastectomy + sentinel lymph node biopsy + tissue expander insertion and replaced with a silicone implant later. Pathological examination revealed that the patient had triple-negative breast cancer. Four courses of doxorubicin+ cyclophosphamide therapy were performed as adjuvant therapy after surgery. We performed genetic counseling and genetic testing, and the results suggested the germline BRCA1 mutation 307 T> A (L63*). She has currently lived without a relapse for 2 years post-surgery. Conclusions There have been only 6 cases of metaplastic breast carcinoma with germline BRCA1 mutations including our case. Patients with BRCA1 mutations may develop basal-like subtypes or M type of triple-negative breast cancer besides metaplastic breast cancers.

Overexpression of HER2 in breast cancer is correlated with poor prognosis. HER2-targeted drugs, such as trastuzumab and lapatinib, have been successful to treat HER2-positive breast cancers, however, the acquisition of the drug resistance of the cells is recognized. Here we suggest the novel molecular targets to cure HER2-positive breast cancers. The oncogenic roles of Rac1, a Rho family small GTPase, in a variety of cancers have been demonstrated. For example, the elevated expression or hyperactivation of Rac1 is frequently observed in human cancers, correlating with their aggressiveness and poor prognosis. In breast cancers, upregulation of Rac1 GEF (GTP exchange factor) and downregulation of Rac1 GAP (GTPase activating protein) have been reported. Moreover, activation of Rac1 contributed to trastuzumab resistance, which poses a serious problem during chemotherapy. In the present study, we first investigated in detail in which subtypes of breast cancers mRNA expression of Rac1 is correlated with their poor prognosis. Using the METABRIC database, we found that high mRNA expression of Rac1 significantly correlated with the poor prognosis of HER2-positive breast cancer (p=0.0012, High: n=49, Low: n=171). On the other hands, other three types (basal, claudin-low, or luminal-B type) did not show significant correlation between the expression levels of Rac1 mRNA and their prognosis (p=0.15, High: n=97, Low: n=102; p=0.052, High: n=110, Low: n=89; p=0.17, High: n=70, Low: n=391; respectively). In luminal-A type breast cancer, low mRNA expression of Rac1 significantly correlated with poor prognosis (p=0.0046, High: n=492, Low: n=187). We next investigated the molecular mechanism underlying Rac1 activation in HER2-positive breast cancer cells, SKBR-3 cells. We found that Cullin-3 (CUL3, a subunit of a RING ubiquitin E3 ligase complex) and its adaptor protein KCTD10 are essential for Rac1 activation. Mechanistically, CUL3/KCTD10 ubiquitinate RhoB, a Rho family small GTPase that suppresses the activation of Rac1, leading to the degradation RhoB. We also found that HER2 signaling is essential for the activation of Rac1. Conclusions: This study reveals that the novel molecular axis CUL3/KCTD10/RhoB regulates the Rac1 activation in HER2-positive breast cancer cells. The interference of CUL3/KCTD10 complex formation may be a new strategy to the treatment of HER2- and Rac1-positive breast cancers. Citation Format: Murakami A, Maekawa M, Kusakabe E, Yamasawa H, Aoki R, Komatsu S, Taguchi K, Nishiyama K, Yamashita M, Sugimori W, Kawai K, Nakayama J, Araki N, Semba K, Taguchi T, Kamei Y, Takada Y, Higashiyama S. Novel mechanisms of Rac1 activation by the Cullin-3/KCTD10 ubiquitin E3 complex in HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-05-02.

Breast cancer subtypes have been classified based on the gene expression profiles, and the specifically effective treatments for each subtype have been developed and applied in clinical situations. However, there is no effective treatment for metaplastic breast carcinomas, which are pathological tissue types with poor prognosis. Metaplastic breast carcinomas are almost resistant to existing chemotherapy because it has not been identified the specific therapeutic target molecules. Recently, Lehmann et al. reported that breast cancers with chondroid metaplasia are categorized in Mesenchymal (M) type, which is one subtype out of six triple negative breast cancer (TNBC) subtypes based on drug susceptibility. From the knowledge on this report, we hypothesized that integrative analyses using the gene expression profile data sets obtained from various types of breast cancers with or without cartilage formation may enable us to identify the therapeutic target genes for metaplastic breast carcinomas, especially for breast cancers with chondroid metaplasia. Bioinformatics analyses were performed using the gene expression profile data sets of TNBC, which are registered in Gene Expression Omnibus (GEO). When compared with metaplastic breast carcinomas (28 data sets), 200 genes were specifically fluctuated over 2-fold in breast cancer with chondroid metaplasia (8 data sets). On the other hand, M type (11 data sets) specific 578 genes were identified over 56 TNBC data sets. In addition, 57 genes were overlapped between chondoroid metaplastic 200 genes and M type 578 genes. Therefore, these 57 overlapped genes might be considered as possible poor prognostic factors in breast cancer with chondroid metaplasia. As a result of Gene Ontology analysis on these 57 genes, skeletal system development and extracellular matrix structural constituent were significantly enriched in Biological process and Molecular function, respectively. Also, SCRG1, SOX8 and SOX10, which are genes related to cartilage differentiation, were included. Next, we focused 14 genes because these genes could serve as therapeutic targets. Then, we validated the expression levels of these 14 genes using tissues obtained from surgically resected human breast cancer with chondroid metaplasia dividing into three parts, the invasive ductal carcinoma, the chondroid metaplasia and normal mammary gland. As a result, SCRG1, CD86, HCLS1, EPSTI1, LYZ, and SLA were significantly increased in chondroid metaplasia part, suggesting that these validated genes were identified as possible therapeutic targets for breast cancer with chondroid metaplasia. Further study will help us to investigate a novel and effective therapeutic strategy for metaplastic breast carcinomas. Citation Format: Yamashita M, Kamei Y, Kusakabe E, Yamasawa H, Aoki R, Taguchi K, Nishiyama K, Murakami A, Sawada Y, Takada Y, Imai Y. Exploring novel therapeutic target molecules for metaplastic breast carcinoma using comprehensive genome-wide gene expression analyses [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-07-07.

CNKSR1 functions as a scaffold protein for activation of an EGFR phosphatase, PTPRH, at the plasma membrane through the exclusive interaction with RhoB-GTP which is constitutively degraded by the CUL3/KCTD10 E3 complex., Epidermal growth factor receptor (EGFR) and human EGFR 2 (HER2) phosphorylation drives HER2-positive breast cancer cell proliferation. Enforced activation of phosphatases for those receptors could be a therapeutic option for HER2-positive breast cancers. Here, we report that degradation of an endosomal small GTPase, RhoB, by the ubiquitin ligase complex cullin-3 (CUL3)/KCTD10 is essential for both EGFR and HER2 phosphorylation in HER2-positive breast cancer cells. Using human protein arrays produced in a wheat cell-free protein synthesis system, RhoB-GTP, and protein tyrosine phosphatase receptor type H (PTPRH) were identified as interacting proteins of connector enhancer of kinase suppressor of Ras1 (CNKSR1). Mechanistically, constitutive degradation of RhoB, which is mediated by the CUL3/KCTD10 E3 complex, enabled CNKSR1 to interact with PTPRH at the plasma membrane resulting in inactivation of EGFR phosphatase activity. Depletion of CUL3 or KCTD10 led to the accumulation of RhoB-GTP at the plasma membrane followed by its interaction with CNKSR1, which released activated PTPRH from CNKSR1. This study suggests a mechanism of PTPRH activation through the exclusive binding of RhoB-GTP to CNKSR1.

Background: The 2019 version 1 of the National Comprehensive Cancer Network guidelines states that magnetic resonance imaging (MRI)-based diagnosis of breast cancer “May be used for staging evaluation to define extent of cancer or presence of multifocal or multicentric cancer in the ipsilateral breast, or as screening of the contralateral breast cancer at time of initial diagnosis.” Therefore, we performed breast MRI to evaluate the extent of spread of breast cancer as part of the preoperative diagnosis. Dual-energy computed tomography (DECT) is a new imaging technology that uses X-ray tube and detectors with two different tube voltages. High-contrast and low-noise images, termed “virtual monochromatic image,” can be obtained using DECT. Recently, clinical cases using DECT have been reported in urology; however, only few cases have been reported on the diagnostic use of DECT for breast cancer. Purpose: Evaluation of the usefulness of DECT in the preoperative diagnosis of extent of breast cancer spread. Patients: Thirty-three patients with breast cancer, who underwent preoperative DECT and MRI, and were operated at our hospital from November 2016 to July 2018. The surgical specimens from the patients were excised horizontally. Patients who underwent preoperative chemotherapy were excluded from the study. Methods: The maximum diameter, including that of the mass and non-mass enhancements in the horizontal sections of each lesion, was retrospectively measured by DECT and MRI. Moreover, the maximum diameter of the invading and intraductal lesions in the horizontal sections of the postoperative pathological sample were retrospectively measured. In addition, the information on the patients’ background, clinical characteristics of the tumor, etc. were retrospectively collected and reviewed from the patients’ electronic medical records. Results: The median age of the patients was 62 years. The median lesion size was 14.3 mm (0-75.8 mm) when measured with DECT, 13.1 mm (0-99.1 mm) with MRI, and 13 mm (3-95 mm) with postoperative pathology. Spearman's rank correlation coefficient was 0.752 (p Subgroup analysis of factors, such as age and menopausal status, showed significant positive correlation in all subgroups. Conclusion: As compared to MRI, DECT is advantageous in that it can simultaneously perform a whole-body metastasis search and scan in the supine position, more closer to the surgical position. Furthermore, in this study, DECT was able to evaluate the extent of spread of lesions, including the intraductal extension, almost similar to that of MRI, suggesting that the diagnostic performance may not differ across subgroups. Additional analysis, such as evaluation of the size of infiltrated area alone, will be conducted and reported in future. Citation Format: Haruna Yamasawa, Akari Murakami, Megumi Takaoka, Erina Kusakabe, Reina Aoki, Kana Taguchi, Kanako Nishiyama, Michiko Yamashita, Wakana Sugimori, Mie Kurata, Mana Fukushima, Riko Kitazawa, Kanako Okada, Megumi Matsuda, Yoshiaki Kamei, Yasutsugu Takada. Evaluating the usefulness of dual-energy computed tomography for the preoperative diagnosis of the extent of spread of breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-02-12.

This study aimed to compare the antiemetic efficacy and safety of a four-drug combination with those of a standard three-drug combination in Japanese patients with breast cancer treated with anthracycline. We retrospectively analyzed data from Japanese patients with breast cancer, who had received their first cycle of anthracycline and were treated with aprepitant, palonosetron, and dexamethasone with or without olanzapine. This retrospective observational study was performed at Ehime University Hospital using the electronic medical records. Multivariable and propensity score-adjusted analyses were performed to compare the onset of complete response (CR) failure between the groups. One-hundred and thirty patients were included in this study and the four- and three-drug group had 22 and 108 patients, respectively. Similar to multivariable logistic regression analysis, propensity-adjusted logistic regression analysis revealed that the four-drug group was markedly associated with a decreased odds of CR failure in the overall, acute, and delayed phases (odds ratio [OR]: 0.27, 95% confidence interval [CI]: 0.10–0.73; OR: 0.28, 95% CI: 0.10–0.76; and OR: 0.15, 95% CI: 0.04–0.57, respectively). Additionally, treatment-related adverse events were well tolerated in both the groups. These findings suggest that the antiemetic efficacy of the four-drug combination is superior to that of the standard three-drug combination.

Rho GTPase Rac1 is a central regulator of F-actin organization and signal transduction to control plasma membrane dynamics and cell proliferation. Dysregulated Rac1 activity is often observed in various cancers including breast cancer and is suggested to be critical for malignancy. Here, we showed that the ubiquitin E3 ligase complex Cullin-3 (CUL3)/KCTD10 is essential for epidermal growth factor (EGF)-induced/human epidermal growth factor receptor 2 (HER2)-dependent Rac1 activation in HER2-positive breast cancer cells. EGF-induced dorsal membrane ruffle formation and cell proliferation that depends on both Rac1 and HER2 were suppressed in CUL3- or KCTD10-depleted cells. Mechanistically, CUL3/KCTD10 ubiquitinated RhoB for degradation, another Rho GTPase that inhibits Rac1 activation at the plasma membrane by suppressing endosome-to-plasma membrane traffic of Rac1. In HER2-positive breast cancers, high expression of Rac1 mRNA significantly correlated with poor prognosis of the patients. This study shows that this novel molecular axis (CUL3/KCTD10/RhoB) positively regulates the activity of Rac1 in HER2-positive breast cancers, and our findings may lead to new treatment options for HER2- and Rac1-positive breast cancers.

Case 1 involved a 75-year-old woman with breast cancer and diffuse large B-cell lymphoma(DLBCL).Although we initially administered the R-CHOP regimen, the breast tumor increased in size and surgery had to be performed.After surgery, the R-CHOP regimen was re-initiated and DLBCL achieved clinical complete response.Case 2 involved a 74-year-old woman with breast cancer and gastric MALT lymphoma.After administration of rituximab and H. pylori eradication, a therapeutic effect was achieved in the lymphoma.A docetaxel and FEC regimen was continuously administered and surgery was performed. Case 3 involved a 62-year-old woman with breast cancer and follicular lymphoma.She presented with a history of DLBCL treatment.We performed mastectomy and sentinel lymph node biopsy, which revealed metastasis of breast cancer, and axillary lymph node dissection was subsequently performed.Considering the pathological stage, adjuvant chemotherapy was needed.We selected the TCH regimen based on her past treatment.In conclusion, it is necessary to treat patients with double presentation of breast cancer and malignant lymphoma through cooperation with different departments.

We report a case of microangiopathic hemolytic anemia(MHA)caused by metastatic breast cancer treated with weekly paclitaxel. A 58-year-old woman was diagnosed with metastatic breast cancer 2 years earlier. She was treated with various chemotherapy regimens and hormonal therapy, before being switched to fulvestrant 3 months earlier. She presented with severe anemia, and was diagnosed with MHA with bone marrow carcinomatosis following bone marrow biopsy. She was treated with weekly paclitaxel and recovered successfully. A subsequent biopsy showed that the bone marrow carcinomatosis had decreased. MHA due to breast cancer is rare and is associated with poor prognosis; however, rapid initiation of chemotherapy may be effective.

Pulmonary tumor thrombotic microangiopathy(PTTM)caused by pulmonary artery microscopic tumor emboli and fibrocellular and/or fibromuscular proliferation leads to progressive pulmonary hypertension and respiratory failure.The prognosis is extremely poor and most patients die shortly after onset.We report a patient with Stage IV breast cancer and long-term survival who developed PTTM during chemotherapy treatment.A 63-year-old woman with multiple metastases in her cerebellum, bone, lung, and lymph node after left breast conserving surgery started to experience dyspnea and malaise 7 years after the surgery.Two months later, she was urgently admitted to hospital because of respiratory failure and was diagnosed with pulmonary hypertension.However, pulmonary thrombosis and tumor thrombus were not observed.We clinically diagnosed her with PTTM and administered chemotherapy in addition to treatment for pulmonary hypertension.Her medical condition improved gradually and she survived for the subsequent 2 years.When observing progressive hypoxia and pulmonary hypertension without obvious pulmonary embolism findings on imaging, PTTM should be considered.Early diagnosis and immediate induction of chemotherapy for primary disease can improve the survival of patients with PTTM.