Humanized Mice as an Effective Evaluation System for Peptide Vaccines and Immune Checkpoint Inhibitors.

Peptide vaccination was developed for the prevention and therapy of acute and chronic infectious diseases and cancer. However, vaccine development is challenging, because the patient immune system requires the appropriate human leukocyte antigen (HLA) recognition with the peptide. Moreover, antigens sometimes induce a low response, even if the peptide is presented by antigen-presenting cells and T cells recognize it. This is because the patient immunity is dampened or restricted by environmental factors. Even if the immune system responds appropriately, newly-developed immune checkpoint inhibitors (ICIs), which are used to increase the immune response against cancer, make the immune environment more complex. The ICIs may activate T cells, although the ratio of responsive patients is not high. However, the vaccine may induce some immune adverse effects in the presence of ICIs. Therefore, a system is needed to predict such risks. Humanized mouse systems possessing human immune cells have been developed to examine human immunity in vivo. One of the systems which uses transplanted human peripheral blood mononuclear cells (PBMCs) may become a new diagnosis strategy. Various humanized mouse systems are being developed and will become good tools for the prediction of antibody response and immune adverse effects.

[Two Cases of Pneumocystis Pneumonia during Adjuvant Chemotherapy for Breast Cancer].

In recent years, human immunodeficiency virus(HIV)-negative Pneumocystis pneumonia(PCP)onset has been occasionally seen in breast cancer. In particular, dose-dense epirubicin and cyclophosphamide(EC: ddEC)therapy, in which EC is administered every 2 weeks, has been generally used in clinical practice for early stage breast cancers. PCP may develop before and during postoperative chemotherapy. We report the cases of 2 patients who developed PCP during postoperative adjuvant chemotherapy. Case 1: A 62-year-old woman, who underwent postoperative EC therapy, developed PCP during the 4th EC cycle. During EC therapy, steroids(prednisolone[PSL])were administered at an average dose of 11.4mg/day, and the number of lymphocytes at the initiation of the 4th EC cycle was 516/mL. Case 2: After receiving 4 cycles of postoperative ddEC, a 27-year-old woman developed PCP after 1 cycle of docetaxel(DTX)administration. During ddEC therapy, PSL was administered at a dose of 17.14mg/day, and the number of lymphocytes at DTX administration was 311/mL. The onset of PCP is presumed to be related to the steroid dose administered and the number of lymphocytes. Therefore, determining effective indicators in patients at a high risk of PCP onset is important.

Comparison of tumor-infiltrating lymphocytes between primary and metastatic tumors in breast cancer patients.

The presence of tumor-infiltrating lymphocytes (TILs) is associated with favorable long-term outcome in breast cancer. However, little is known about changes in TILs during metastatic progression. To confirm our hypothesis that malignant tumors escape from the host immune system during metastasis, we evaluated the percentage of TILs in paired samples of primary and metastatic breast tumors. We retrospectively identified 25 patients with human epidermal growth factor receptor-2 (HER2+ , n = 14) and triple negative (TN, n = 11) early breast cancer diagnosed between 1990 and 2009 at Tokai University Hospital (Isehara, Japan) and who subsequently experienced regional or distant recurrence confirmed by tumor biopsy/resection. Hematoxylin-eosin-stained slides of these paired samples were evaluated for stromal TILs. Immunohistochemical staining was carried out using primary antibodies against CD4, CD8, Foxp3, programmed cell death ligand 1 (PD-L1), PD-L2, and HLA class I for characterizing the TILs and breast tumors. The percentage of TILs in the primary tumors was significantly higher (average 34.6%) than that in metastatic tumors (average 15.7%) (paired t-test, P = 0.004) and that of CD8+ and CD4+ T cells significantly decreased from primary to metastatic tumors (paired t-test, P = 0.008 and P = 0.026, respectively). The PD-L1, PD-L2, and HLA class I antibody expression changed from positive to negative and vice versa from the primary to the metastatic tumors. Tumors at first metastatic recurrence in HER2+ and TN breast cancers have a lower percentage of TILs and CD8+ and CD4+ T cells compared to primary tumors, which indicates that immune escape plays a role in tumor progression.

Feasibility and pharmacokinetics of combined therapy with S-1 and trastuzumab in patients with human epidermal growth factor receptor 2-positive metastatic or recurrent breast cancer.

BACKGROUND: To clarify the tolerance and pharmacokinetics of combined therapy with S-1 and trastuzumab in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic or recurrent breast cancer. METHODS: From January 2008 through to September 2009, combined therapy with S-1 and trastuzumab was given to 7 patients with HER2-positive metastatic or recurrent breast cancer. The incidence of adverse events and the pharmacokinetics of tegafur, 5-fluorouracil, and gimeracil in plasma were studied. RESULTS: One patient had grade 3 leukopenia, and another had a grade 3 elevation of alanine aminotransferase. All other adverse events were grade 2 or lower. The combination of S-1 and trastuzumab did not cause any new adverse events. The incidence of adverse events was similar to those associated with S-1 alone. The median number of treatment cycles was 11. The pharmacokinetics of tegafur, 5-fluorouracil, and gimeracil after treatment with S-1 plus trastuzumab did not markedly differ from those after S-1 alone. CONCLUSIONS: Combined therapy with S-1 and trastuzumab did not cause any new adverse events, administration continuity was good, and the therapy was well tolerated.

Efficacy of Nursing Interventions Using Motivational Interviewing Aimed at Weight Loss in Overweight/Obese Breast Cancer Patients Undergoing Endocrine Therapy.

OBJECTIVE: Obesity adversely impacts breast cancer treatment and outcomes. This study assessed the efficacy of nurses' motivational interviews (MI) in promoting weight loss among breast cancer patients. METHODS: Motivational Interviewing was performed at 4, 8, and 12 weeks from baseline in 27 overweight/ obese breast cancer patients receiving adjuvant endocrine therapy. An average weight loss rate of 5% at week 12 was the threshold for determining whether MI intervention was clinically meaningful. Clinical and sociodemographic variables were gathered from medical records and self-administered questionnaires. Body weight, body mass index (BMI), physical activity time, sedentary time, self-efficacy for weight loss, and mood scores were evaluated at baseline, 4, 8, 12, and 24 weeks. RESULTS: Significant reductions in body weight were observed throughout compared with baseline; 51.9% of participants attained the 5% weight loss target, but the average weight loss rate was 3.9% at week 12. BMI notably decreased at 8, 12, and 24 weeks compared with baseline. Physical activity increased significantly at 12 weeks, while sedentary time decreased at 8 and 24 weeks. CONCLUSIONS: Nursing-administered MI did not achieve the goal of 5% weight loss at week 12. However, it increased physical activity and reduced sedentary time, showing potential for promoting healthier habits.

Coccomyxa subellipsoidea KJ Components Enhance the Expression of Metallothioneins and Th17 Cytokines during Human T Cell Activation.

Coccomyxa subellipsoidea KJ (C-KJ) is a green alga with unique immunoregulatory characteristics. Here, we investigated the mechanism underlying the modification of T cell function by C-KJ components. The water-soluble extract of C-KJ was fractionated into protein (P) and sugar (S) fractions acidic (AS), basic (BS), and neutral (NS). These fractions were used for the treatment of peripheral blood mononuclear cells stimulated with toxic shock syndrome toxin-1. Transcriptome analysis revealed that both P and AS enhanced the expression of the genes encoding metallothionein (MT) family proteins, inflammatory factors, and T helper (Th) 17 cytokine and suppressed that of those encoding Th2 cytokines in stimulated T cells. The kinetics of MT1 and MT2A gene expression showed a transient increase in MT1 and maintenance of MT2A mRNA after T cell stimulation in the presence of AS. The kinetics of Th17-related cytokine secretion in the early period were comparable to those of MT2A mRNA. Furthermore, our findings revealed that static, a STAT-3 inhibitor, significantly suppressed MT2A gene expression. These findings suggest that the expression of MTs is involved in the immune regulatory function of C-KJ components, which is partially regulated by Th17 responses, and may help develop innovative immunoregulatory drugs or functional foods.

Construction of the systemic anticancer immune environment in tumour-bearing humanized mouse by using liposome-encapsulated anti-programmed death ligand 1 antibody-conjugated progesterone.

Immune checkpoint inhibitors highlight the importance of anticancer immunity. However, their clinical utility and safety are limited by the low response rates and adverse effects. We focused on progesterone (P4), a hormone produced by the placenta during pregnancy, because it has multiple biological activities related to anticancer and immune regulation effects. P4 has a reversible immune regulatory function distinct from that of the stress hormone cortisol, which may drive irreversible immune suppression that promotes T cell exhaustion and apoptosis in patients with cancer. Because the anticancer effect of P4 is induced at higher than physiological concentrations, we aimed to develop a new anticancer drug by encapsulating P4 in liposomes. In this study, we prepared liposome-encapsulated anti-programmed death ligand 1 (PD-L1) antibody-conjugated P4 (Lipo-anti-PD-L1-P4) and evaluated the effects on the growth of MDA-MB-231 cells, a PD-L1-expressing triple-negative breast cancer cell line, in vitro and in NOG-hIL-4-Tg mice transplanted with human peripheral blood mononuclear cells (humanized mice). Lipo-anti-PD-L1-P4 at physiological concentrations reduced T cell exhaustion and proliferation of MDA-MB-231 in vitro. Humanized mice bearing MDA-MB-231 cells expressing PD-L1 showed suppressed tumor growth and peripheral tissue inflammation. The proportion of B cells and CD4+ T cells decreased, whereas the proportion of CD8+ T cells increased in Lipo-anti-PD-L1-P4-administrated mice spleens and tumor-infiltrated lymphocytes. Our results suggested that Lipo-anti-PD-L1-P4 establishes a systemic anticancer immune environment with minimal toxicity. Thus, the use of P4 as an anticancer drug may represent a new strategy for cancer treatment.

Immunohistochemical Ki67 labeling index has similar proliferation predictive power to various gene signatures in breast cancer.

The objective of this study was to examine the association between the immunohistochemical Ki67 labeling index (IHC Ki67), Ki67 mRNA expression level, and first-generation gene signatures in a cohort of breast cancer patients. We assessed associations between IHC Ki67 and first-generation gene signatures in a panel of 39 tumor samples, using an oligonucleotide microarray. Gene expression analyses included Ki67 alone (MKi67), 21-gene signature, mitosis kinome score signature, and genomic grade index. Correlation coefficients were calculated by Spearman's rank correlation test. In all cases, IHC Ki67, MKi67, and three genetic markers were highly correlated (ρ, 0.71-0.97). Estrogen receptor (ER)-positive cases showed strong correlations between IHC Ki67 and other signatures (ρ, 0.79-0.83). The ER-negative cases showed slightly lower correlations (ρ, 0.58-0.73). In ER-positive cases, the low IHC Ki67 group showed significantly longer relapse-free survival than the high IHC Ki67 group (P = 0.007). This difference was confirmed by multivariate analysis. Our data indicate that IHC Ki67 shows similar predictive power for proliferation in ER-positive cancers as genomic markers. Further study of IHC Ki67 is needed to define prognostic factors and predictive factors for chemotherapy using central laboratory assessment.

Can a Relationship of Trust Be Built Between Student Doctors and Patients Through Remote Interviews During COVID-19?

INTRODUCTION: Clinical clerkships could not be conducted as usual in 2021, due to the COVID-19 pandemic. We conducted a questionnaire survey of medical students and patients to determine whether remote medical interviews conducted in such a scenario could build a trusting relationship between the two. MATERIALS AND METHODS: Fifth-year students at Tokai University School of Medicine conducted tablet-based medical interviews (remote medical interviews) with patients as part of their clinical clerkship of breast endocrine surgery. Later, both the patients and students had to rate the trustworthiness of their relationship and their preference for remote/face-to-face medical interviews in a questionnaire survey. Forty-three students and 42 patients took part in the survey. RESULTS AND DISCUSSION: All the patients and students agreed that a trusting relationship had been established. The results showed that most of the students preferred remote medical interviews, but patients were very divided in their preferences between face-to-face and remote medical interviews. Overall, we may conclude that remote medical interviews could be a safe tool for clinical practice in the future.

Immunological profiles of the breast cancer microenvironment represented by tumor-infiltrating lymphocytes and PD-L1 expression.

Tumor-infiltrating lymphocytes (TILs) and programmed cell death 1 ligand 1 (PD-L1) are established prognostic and predictive biomarkers for certain breast cancer subsets. However, their association with the immune response complexity is not fully understood. Therefore, we analyzed the association between the immune cell fractions in breast cancer tissues and histologically assessed TIL (hTIL) and PD-L1 (hPD-L1). Forty-five tumor and eighteen blood samples were collected from patients with breast cancer. Total leukocyte counts, frequency of 11 immune cell populations, and PD-L1 expression in each cell fraction were evaluated by flow cytometry. TILs and PD-L1 were assessed by hematoxylin and eosin staining and immunohistochemistry, respectively. A higher hTIL score showed association with increased leukocyte infiltration, higher CD4+ and CD8+ T cell proportions, and lower natural killer and natural killer T cell proportions. PD-L1 was highly expressed in nonclassical monocytes, monocyte/macrophages, myeloid-derived suppressor cells, myeloid dendritic cells, dendritic cells, and other lineages in tumors. hPD-L1 positivity reflected PD-L1 expression accurately in these fractions, as well as increased leukocyte infiltration in tumors. These results indicate that hTILs reflect differences in the immune responses in the tumor microenvironment, and certain immune cell fractions are favorably expressed in the PD-L1 pathway in breast cancer microenvironments.

High-progesterone environment preserves T cell competency by evading glucocorticoid effects on immune regulation.

Progesterone (P4) and glucocorticoid (GC) play crucial roles in the immunoregulation of a mother to accept and maintain a semi-allogenic fetus. P4 concentration increases during pregnancy and becomes much higher in the placenta than in the other peripheral tissues, wherein the concentration of cortisol (COR), the most abundant GC and a strong immunosuppressor, remains uniform throughout the rest of the body. Here, we evaluated the effect of a high-P4 environment on pregnant immunity by comparing it with COR. Naïve T cell proportion increased transiently in peripheral blood of pregnant women just after delivery and decreased after one month. T cells stimulated with superantigen toxic-shock-syndrome-1 (TSST-1) in the presence of P4 stayed in the naïve state and did not increase, irrespective of the presence of COR, and reactive T cells could not survive. Treatment of T cells with P4 without T cell receptor (TCR) stimulation transiently suppressed T cell activation and proliferation, whereas the levels remain unaltered if P4 was not given before stimulation. Comparison of the engraftment and response against specific antigens using hu-PBL-NOG-hIL-4-Tg mice showed that P4-pretreated lymphocytes preserved CD62L expression and engrafted effectively in the spleen. Moreover, they produced antigen-specific antibodies, whereas COR-pretreated lymphocytes did not. These results suggest that a high-P4 environment suppresses T cell activation and induces T cell migration into lymphoid tissues, where they maintain the ability to produce anti-pathogen antibodies, whereas COR does not preserve T cell function. The mechanism may be pivotal in maintaining non-fetus-specific T cell function in pregnancy.

Post-marketing safety evaluation of S-1 in patients with inoperable or recurrent breast cancer: especially in patients treated with S-1 + trastuzumab.

OBJECTIVE: The purpose of this study was to assess the safety of S-1 in Japanese in inoperable or recurrent breast cancer patients. METHODS: A prospective post-marketing surveillance was performed at 313 sites in Japan in patients with inoperable or recurrent breast cancer treated with S-1. We examined 1361 patients between January 2006 and December 2007 with regard to the incidence of adverse drug reactions graded by the Common Terminology Criteria for Adverse Events (CTCAE), version 3.0. RESULTS: At least one adverse drug reaction was encountered by 858 patients, with an overall incidence of 63.0% (858/1361). The incidence of Grade 3 or higher adverse drug reactions in a descending order was 14.7% (200/1361). In this study, the most common combination drug was trastuzumab. The overall incidence of adverse drug reactions was 63.5% (431/679 patients) in patients treated with S-1 alone, and 55.9% (66/118 patients) in patients treated with S-1 + trastuzumab. CONCLUSIONS: Monotherapy with S-1 or combination therapy with S-1 + trastuzumab was well tolerated for inoperable or recurrent breast cancer patients.

Introducing a Remote Pre-graduate Medical Education Curriculum Planning Workshop During the COVID-19 Pandemic.

PURPOSE: To conduct a thorough online workshop on infection control under COVID-19 and to conduct a questionnaire survey on the online workshop. OBJECTIVE: The Tokai University School of Medicine has held 39 workshops to acquire the curriculum planning ability required as a faculty member of the School of Medicine. Due to the COVID-19 pandemic, this year (2020) we were unable to hold a workshop. Therefore, we attempted an online workshop using Zoom. METHODS: To shorten the amount of time required for the workshop, we excluded some content that was used the previous year. The day passed without any major problems, and both the participants and the individuals in charge of the workshop filled out a questionnaire at the end of the day. RESULTS: Conclusion: Online workshops appear to be a very useful tool in terms of infection control under the COVID-19 pandemic.

HER2-antigen-specific humoral immune response in breast cancer lymphocytes transplanted in hu-PBL hIL-4 NOG mice.

The status of humoral immunity of cancer patients is not clear compared to cellular immunity because the ability of specific antibody production is difficult to analyze in vitro. We previously developed a humanized mouse model to evaluate antigen-specific antibody production by transplanting human peripheral blood mononuclear cells (PBMCs) into NOG-hIL-4-Tg mice (hu-PBL hIL-4 NOG). In this study, these mice were transplanted with PBMCs derived from breast cancer patients (BC) and immunized with a human epidermal growth factor receptor 2 (HER2) peptide, CH401MAP, to analyze humoral immunity of BCs. The hu-PBL hIL-4 NOG mice recapitulated immune environment of BCs as the ratio of CD8+/CD4+T cells was lower and that of PD-1 + T cells was higher compared to healthy donors (HDs). Diverse clusters were detected in BC-mouse (BC-M) plasma components involving immunoglobulins and complements unlike HD-M, and there was a significant diversity in CH401MAP-specific IgG titers in BC-M. The number of B cell clones producing high CH401MAP-specific IgG was not increased by immunization in BC-M unlike HD-M. These results demonstrated that the humoral immunity of BCs appeared as diverse phenotypes different from HDs in hu-PBL hIL-4 NOG mice, which may provide important information for the study of personalized medicine.

[Breast cancer].

Almost all breast cancer patients are treated with chemotherapy, hormone therapy, molecular targeted therapy, radiotherapy, and surgery alone or in combination. It is reasonable and standard to choose a combination according to clinical practice guidelines. One of the objectives of clinical practice guidelines is to standardize medical care and provide equal quality of care for patients wherever they live in Japan. Recently, many clinical trials have been conducted internationally. Therefore, it is necessary to standardize medical care from an international viewpoint. In this paper, the breast cancer clinical practice guideline developed by the Japanese Breast Cancer Society was compared with other guidelines which have been already developed and are frequently utilized all over the world as well as in Japan.

Stability of HER2 Status by Dual-color in Situ Hybridization Before and After Neoadjuvant Chemotherapy in Breast Cancer.

OBJECTIVE: Trastuzumab may convert human epidermal growth factor receptor-2 (HER2)-positive primary breast tumors to HER2-negative tumors after chemotherapy. This study determined whether trastuzumab increases the number of patients with conversion to HER2-negative status and assessed the effect of neoadjuvant chemotherapy. METHODS: We retrospectively reviewed 46 patients diagnosed with HER2-overexpression in primary breast cancers at Tokai University Hospital, receiving neoadjuvant chemotherapy by immunohistochemistry and fluorescence in situ hybridization (FISH). Surgical specimens of patients achieving less than pathological complete response (pCR) were verified for sufficient residual tissue to evaluate post-treatment HER2 status by dual-color in situ hybridization (DISH). RESULTS: pCR was achieved in 8 of the 46 (17.4%) patients. The residual tumor was sufficient for a ssessing post-treatment HER2 status in 25 patients. DISH of pretreatment specimens confirmed HER2 amplification prior to therapy. Of the 25 HER2-positive patients, DISH revealed 3 were HER2 negative in pretreatment specimens. No post-treatment tumors were HER2-negative according to DISH in HER2-positive pre-treatment tumors. Among HER2-negative pretreatment tumors, 1 post-treatment tumor was HER2 positive and 2 had stable HER2 status. CONCLUSION: HER2 status determined by DISH was stable between pretreatment breast tumors and residual tumors. However, a small discrepancy regarding HER2 status determined by immunohistochemistry and DISH existed.

Students' Input on Preparing a Weekly Calendar of Individual Students in the Breast Surgery Clinical Clerkship.

Background; Until 2018, the Breast and Endocrine surgery had no student calendar. A questionnaire survey was conducted on how students felt by creating a weekly schedule of individual students from 2019. METHOD: 6th-year elective courses, targeted at students who selected Breast and Endocrine surgery clinical clerkship. The schedule clarifies the contents of the training as follows; outpatient visits, small group study (preparation for graduation and national exams including mammography reading), simulator training, and surgery. The questionnaire adopted an anonymous five-point evaluation method (5; I think very much; 4; Somewhat I think; 3; Normal; 2; Somewhat I don't think; 1; I don't think), and provided a free text box. The following seven questions were asked; A. I was able to send a good training, B. I was useful for studying national and graduation exams, C. Time constraints were appropriate, D. I could fully experience surgery, E. Appropriately experienced outpatients, F. Assignments (presented at conference) appropriate, G. I was interested in Breast and Endocrine surgery. RESULTS: Average values were A. 4.7, B. 4.9, C. 4.6, D. 4.9, E. 4.8, F. 4.7, G. 4.7. However, C and F received low ratings of 1 and 2. In the free text box, there were favorable opinions such as the fact that it was good to prepare for the national examination and that reading mammography was helpful. Conversely, there were some negative opinions, such as a time spent outpatient was too long, a difference in enthusiasm among the instructors, and a hope to see more at the first visit and to cope with the procedure. DISCUSSION: Preparing a weekly calendar of individual students generally yielded satisfactory results, but also highlighted the potential for future improvements in clinical clerkship.

Taste alterations in patients with breast cancer following chemotherapy: a cohort study.

BACKGROUND: Chemotherapy-induced taste and smell alterations in cancer patients are associated with multiple adverse effects, namely, malnutrition, weight loss, and a diminished quality of life. The aim of this prospective study was to identify the incidence of taste alterations following epirubicin and cyclophosphamide (EC) chemotherapy in patients with breast cancer without previous history of cancer or chemotherapy. METHODS: Forty-one patients undergoing EC chemotherapy for breast cancer at Tokai University Hospital were included. A subjective (questionnaire) and an objective (filter paper disk method) assessment for 5 basic tastes were administered on day 4 post-chemotherapy and immediately before the subsequent cycle of chemotherapy for each cycle, in addition to an olfactory evaluation and oral examination. The correlation between subjective and objective taste alterations and factors influencing these alterations were analyzed by statistical means. RESULTS: The mean incidence of subjective taste alteration on the 4th day after chemotherapy was 53%. In each of the 4 cycles, taste alterations decreased to about 9.0% immediately before the next cycle. A significant correlation between subjective and objective assessments was seen only for salty taste, suggesting important differences in subjective versus objective assessment outcomes. A multivariate analysis indicated that age and body surface area influenced taste alterations. CONCLUSIONS: EC chemotherapy induced taste alterations in more than 50% of patients, which decreased to less than 10% immediately before the next chemotherapy cycle. A combination of objective and subjective assessments is essential to evaluate taste alterations induced by EC chemotherapy. These could be used in routine clinical practice.

Myxofibrosarcoma that Developed Rapidly in the Breast of an Elderly Man and Recurred Early after Surgery: A Case Report.

BACKGROUND: Myxofibrosarcoma is a rare disease occurring subcutaneously in the limbs. We report a case of a rapidly growing myxofibrosarcoma in the breast of an elderly man that recurred early after surgery. CASE PRESENTATION: A 73-year-old man presented with a breast mass. Physical findings showed a large tumor in the right breast, and malignancy was suspected on ultrasonography. Computed tomography (CT) revealed tumor invasion into the pectoralis major and pectoralis minor muscles. Positron emission tomography/CT showed no abnormality in other organs. Needle biopsy results excluded breast cancer but did not provide a definitive diagnosis. However, the tumor grew rapidly before further results were available, so emergency mastectomy was performed. The final pathological diagnosis was high-grade myxofibrosarcoma. Postoperative radiotherapy was started because of remnant tumor. The wound became worsened and swollen, and needle biopsy 10 days after the start of therapy indicated recurrence. Radical resection and thoracoplasty were performed. Postoperative pathological specimens showed no residual tumor. Radical radiation therapy was resumed. The patient has shown no recurrence after an year. CONCLUSIONS: It is important to consult a soft tissue oncologist for tumors in the breast and perform appropriate examination and treatment if soft tissue tumors cannot be ruled out.

A Case of Unknown Primary Cancer with a Tumor Formed in the Retroperitoneum: A Case Report.

BACKGROUND: Cancer of unknown primari (CUP) are said to account for 2% of all carcinomas. Here we report a rare case of CUP confined to the retroperitoneum. CASE PRESENTATION: A 51-year-old man consulted a nearby physician for back pain. The malignant tumor could not be denied by MRI, and she was referred to our hospital. CT and MRI revealed uneven enhanced tumor structures protruding into the L2/3 disc. Part of the tumor was continuous with the left iliopsoas muscle. A CT-guided needle biopsy was performed. Histologically, the sheet-like proliferation of atypical cells was observed. Immunohistochemistry showed that atypical cells were positive for cytokeratin AE1&3, CK7, CD10, GATA3, glypican 3, Hep Par 1, carbonic anhydrase 9 (focal), and vimentin (focal) but negative for CK20, CD56, chromogranin A, synaptophysin, TTF1, HMB45, melan A, and PSA. The pathological diagnosis was poorly differentiated carcinoma. However, it was difficult to determine the primary site from the pathological findings. Positron emission tomography (PET) scan showed no distant metastases. He was diagnosed as poorly differentiated cancer localized to the lumbar spine from the retroperitoneum. Paclitaxel plus carboplatin (TC) was started. After completing 3 kr of TC, she was hospitalized urgently due to worsening lumbago. CT and MRI at admission showed an increase in the main lesion and exacerbation of bone invasion. Radiation therapy was given for curative purposes. Eventually, he died seven months after visiting our hospital and five months after starting TC therapy. CONCLUSIONS: CUP has various disease states, and it is necessary to finish the examination immediately and shift to treatment. More effective treatment including immune checkpoint inhibitor for CUP is needed in the future.