Predominance of T-bet-positive Th1 cells in infiltrating T-lymphocytes in most of active arteritis lesions of giant cell arteritis.

Immunological mechanisms through the activation of CD4-positive T-cells have been assumed to be involved in the pathogenesis of giant cell arteritis (GCA). Many studies employing frozen tissues of temporal artery biopsy, peripheral blood lymphocytes, and plasma of GCA patients have revealed the contribution of interferon-γ and interleukin-17 in both protein and mRNA levels. However, the analyses using formalin-fixed and paraffin-embedded (FFPE) tissue specimens, in which the correlation between histopathologic pictures and immunological circumstances would be elucidated, have been limited. Here, we performed the immunohistochemical analyses of infiltrating small lymphocytes in GCA lesions using FFPE specimens, especially of the subsets of CD4-positive T-cells by immunohistochemistry with antibodies against T-bet, GATA-3, RORγT, and Foxp3, which is the differentiation-specific transcription factor for Th1, Th2, Th17, and Treg cells, respectively. In these slides, the nuclear-positive staining is much more clearly and easily identifiable than the cytoplasmic staining for cytokines. The results indicate the predominance of T-bet-positive Th1 cells in infiltrating T-cells in most of active arteritis lesions of GCA. Furthermore, our data suggest the possible immunosuppressive microenvironment induced by T-reg cells and M2-type macrophages in the arteritis lesions throughout the course of GCA inflammation.

Validation of the Diagnostic Criteria for IgG4-Related Periaortitis/Periarteritis and Retroperitoneal Fibrosis (IgG4PA/RPF) 2018, and Proposal of a Revised 2023 Version for IgG4-Related Cardiovascular/Retroperitoneal Disease.

BACKGROUND: In 2018, diagnostic criteria were introduced for IgG4-related periaortitis/periarteritis and retroperitoneal fibrosis (PA/RPF). This study assessed the existing criteria and formulated an improved version.Methods and Results: Between August 2022 and January 2023, we retrospectively analyzed 110 Japanese patients diagnosed with IgG4-related disease (IgG4-RD) involving cardiovascular and/or retroperitoneal manifestations, along with 73 non-IgG4-RD patients ("mimickers") identified by experts. Patients were stratified into derivation (n=88) and validation (n=95) groups. Classification as IgG4-RD or non-IgG4-RD was based on the 2018 diagnostic criteria and various revised versions. Sensitivity and specificity were calculated using experts' diagnosis as the gold standard for the diagnosis of true IgG4-RD and mimickers. In the derivation group, the 2018 criteria showed 58.5% sensitivity and 100% specificity. The revised version, incorporating "radiologic findings of pericarditis", "eosinophilic infiltration or lymphoid follicles", and "probable diagnosis of extra-PA/-RPF lesions", improved sensitivity to 69.8% while maintaining 100% specificity. In the validation group, the original and revised criteria had sensitivities of 68.4% and 77.2%, respectively, and specificities of 97.4% and 94.7%, respectively. CONCLUSIONS: Proposed 2023 revised IgG4-related cardiovascular/retroperitoneal disease criteria show significantly enhanced sensitivity while preserving high specificity, achieved through the inclusion of new items in radiologic, pathological, and extra-cardiovascular/retroperitoneal organ categories.

Intrahepatic Cholangiocarcinoma with High Microsatellite Instability and Tumor Mutation Burden That Responded Significantly to Pembrolizumab but Perforated within a Short Period.

Cholangiocarcinoma has a poor prognosis, and resection is the only curative treatment. Pembrolizumab, a programmed death receptor 1 inhibitor, has proven effective against unresectable or metastatic solid tumors with high microsatellite instability (MSI-H) or a high tumor mutation burden (TMB-H). In the present case, pembrolizumab treatment was initiated after standard chemotherapy for MSI-H and TMB-H unresectable intrahepatic cholangiocarcinoma. Intrahepatic tumor necrosis perforated the abdominal cavity. Emergency surgery was performed, but the patient died 36 days after admission. A pathological autopsy revealed that the intrahepatic tumor had almost completely disappeared.

Progress testing of an objective structured clinical examination during undergraduate clinical clerkship: a mixed-methods pilot study.

BACKGROUND: Progress testing is an assessment method in which an examination reflecting competencies at graduation is regularly administered to students over multiple years, thereby facilitating self-directed learning. However, the significance of the objective structured clinical examination as a progress test in undergraduate education, needs to be determined. This study provides evidence of the role of the objective structured clinical examination for progress testing and optimal scoring methods for assessing students in different academic years. METHODS: We conducted a sequential explanatory mixed-methods pilot study. Participants were assessed using the Item Rating Scale, the year-adjusted Global Rating Scale, and the Training Level Rating Scale. The characteristics of each scale were compared quantitatively. In addition, the influence of the objective structured clinical examination as a progress test on learning attitudes was examined. Qualitative data from a post-examination questionnaire were analyzed, using content analysis to explore influences on self-directed learning. RESULTS: Sixth and fifth year clinical students (n = 235) took the objective structured clinical examination progress test. The total Item Rating Scales were recorded (%) as 59.03 ± 5.27 and 52.64 ± 5.08 (p < 0.01); Training Level Rating Scale was 3.94 ± 0.39 vs 3.22 ± 0.42 (p < 0.01); and the year-adjusted Global Rating Scale was 4.25 ± 0.44 vs 4.32 ± 0.52 (no significant difference), for the sixth and fifth year students, respectively. The correlations across stations and the reliability of each station were satisfactory. Four categories were identified in the qualitative analysis: "motivation to learn during the clinical clerkship was promoted," "dissatisfied with being asked about things they had not experienced," "confusion about being unable to use conventional test-taking strategies," and "insufficient understanding of competencies at graduation." The scores indicated significant differences in performance according to training year. CONCLUSIONS: This study provides evidence that the objective structured clinical examination can be used as a progress testing tool for undergraduate clinical clerkships. Further enhancement of training opportunities and dissemination of performance competency goals in clerkship curricula are required if we intend to promote self-directed learning through progress testing.

Establishment of Epstein-Barr Virus (EBV) Latent Gene-Expressing T-Cell Lines with an Expression Vector Harboring EBV Nuclear Antigen 1.

Chronic active Epstein-Barr virus (EBV) infection (CAEBV) is characterized by chronic or recurrent infectious mononucleosis-like symptoms and is associated with EBV-associated T/natural killer (NK)-cell lymphoproliferative disorders, which frequently lead to the development of life-threatening complications, such as virus-associated hemophagocytic syndrome and EBV-positive apparent leukemia/lymphoma mainly in T- and NK-cell lineages. In order to clarify the EBV genes responsible for the diseases, we introduced the plasmid coding sequences of EBV-encoded small RNAs (EBERs) and/or latent membrane protein (LMP) 1 into human T-lymphocyte virus-I-negative human T-cell lines using a gene expression vector harboring EBV nuclear antigen 1, established the G418-resistant transformants of five T-cell lines, and quantitatively examined the expression of EBERs and LMP1 using real-time reverse transcriptase-polymerase chain reaction. The expression levels of EBERs in T-cell transformants with EBER DNA paralleled those in EBV-positive human T- and NK-cell lines, SNTK cells. The expression of LMP1 mRNA varied in SNTK cells and in human T-cell transformants, and the expression of LMP1 mRNA in T-cell lines expressing both EBERs and LMP1 was much lower than that in the same cell line expressing LMP1 mRNA alone. The currently employed gene expression system and currently obtained transformants may be useful for the analyses of the pathophysiology of CAEBV and EBV-positive T/NK-cell lymphoproliferative disorders.

Expert perspectives on pathological findings in vasculitis.

Pathological findings are important in the diagnosis of vasculitis. However, due to the rarity of the disease, standard textbooks usually devote only a few pages to this topic, and this makes it difficult for clinicians not specializing in vasculitis to fully understand the pathological findings in vasculitis. To address the paucity of information, we present representative pathological findings in vasculitis classified in the 2012 Revised International Chapel Hill Consensus Conference Nomenclature of Vasculitides (CHCC2012). The CHCC2012 classifies 26 vasculitides into seven categories: (1) large-vessel vasculitis, (2) medium-vessel vasculitis, (3) small-vessel vasculitis, including antineutrophil cytoplasmic antibody-associated vasculitis and immune complex small-vessel vasculitis, (4) variable-vessel vasculitis, (5) single-organ vasculitis, (6) vasculitis associated with systemic disease, and (7) vasculitis associated with probable aetiology. Moreover, representative pathological findings of vasculitis-related diseases and non-inflammatory vasculopathy not mentioned in the CHCC2012 are also presented. This will be useful for clinicians to refer to typical pathological findings of vasculitis in daily practice.

An autopsy case of fulminant myocarditis after severe acute respiratory syndrome coronavirus 2 vaccine inoculation.

A 61-year-old woman without significant medical history developed fever 3 days after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination and went into shock the next day. She was negative for SARS-CoV-2 mRNA in real-time polymerase chain reaction (PCR). Finally, she died 10 days after vaccination. At autopsy, the heart showed moderate dilatation of both ventricles, and the myocardium showed an uneven color change and decreased elasticity. Histologically, severe myocarditis with extensive myocytolysis was observed. The myocarditis showed severe inflammatory cell infiltration with T-lymphocyte and macrophage predominance, and in addition to the inflammatory cells described above, vast nuclear dust accompanying neutrophilic infiltration was observed. In the bone marrow and lymph nodes, hemophagocytosis was observed. In postmortem examination, nucleic acids of any cardiotropic viruses including SARS-CoV-2 were not detected using multivirus real-time PCR system. We discussed the relationship between the possible immune reaction after vaccination and the myocarditis observed in this case from immunopathological viewpoints. This mRNA vaccine is the first applied nucleic acid vaccine for humans, and its mechanism of efficacy and immune acquisition remain unclear. We hope the accumulation of more detailed analyses of the similar cases to reveal the mechanism of this kind of adverse reaction.

Spread of vimentin-immunoreactive cells within the plaque-like lesion in the spinal anterior horn of a patient with post-poliomyelitis syndrome.

A Japanese man in the present study experienced acute weakness in his right leg as a two year old. The strength in his leg gradually recovered and developed, and he could play golf and climb mountains up to around the age of 50. From approximately 55 years of age, he became unable to stand up from a stooped position. Muscle weakness and atrophy spread to his right arm, and an electromyography revealed a neurogenic pattern in his lower and upper extremities. The patient was diagnosed as having post-poliomyelitis syndrome (PPS). Numbness in both the legs and pain in the buttocks occurred after 60 years of age. Computed tomography and magnetic resonance imaging at that time revealed spondylosis and protrusion of an osteophye in lower thoracic vertebrae compressing the second lumbar segment of the spinal cord. He died of malignant lymphoma and acute interstitial pneumonia at 80 years of age. Pathological examination revealed transverse myelopathy at the second lumbar segment of the spinal cord and total necrosis. The anterior horn and the intermediate zone of the third and fourth lumbar segments of the spinal cord on the right side were atrophic and diffusely gliotic. An oval-shaped plaque-like lesion was observed in the right anterior horn at the third and fourth lumbar segments of the spinal cord. Neurons and synaptophysin immunoreactivity had completely disappeared in the plaque-like lesion. A striking spread of vimentin-immunoreactive cells was found corresponding to the lesion, while glial fibrillary acidic protein-immunoreactive astrocytes existed evenly in the anterior horn and intermediate zone on both sides of the third and fourth lumber segments of the spinal cord. Virological examination using the autopsied materials was negative for poliovirus. Neither transactivation response DNA-binding protein of 43 kDa-immunoreactive inclusion nor Bunina body was seen in the spinal cord. The present paper demonstrates new findings of a noteworthy response of the vimentin-immunoreactive cells within the peculiar "plaque-like lesion" in the PPS.

Histologic and Immunohistochemical Evaluation of Infiltrating Inflammatory Cells in Kawasaki Disease Arteritis Lesions.

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology which predominantly affects medium- and small-sized muscular arteries. Histopathologic studies of KD vasculitis lesions have demonstrated characteristic T cell infiltration and an abundance of CD8 T cells; however, the contribution of cytotoxic lymphocytes to KD vasculitis lesions has not been identified. Here, we histopathologically and immunohistochemically examined infiltrating inflammatory cells, particularly cytotoxic protein-positive cells, such as granzyme B cells and TIA-1 cells, in KD vasculitis lesions. Three autopsy specimens with acute-phase KD were observed and contained 24 vasculitis lesions affecting medium-sized muscular arteries, excluding pulmonary arteries. Infiltrating neutrophils in vasculitis lesions were evaluated by hematoxylin and eosin staining, and monocytes/macrophages and lymphocytes were evaluated by immunohistochemistry. The predominant cells were CD163 monocytes/macrophages and CD3 T cells. CD8 T cells, granzyme B cells, and TIA-1 cells were also observed, but CD56 natural killer cells were rare. To the best of our knowledge, the current study is the first histopathologic report confirming the infiltration of inflammatory cells with cytotoxic proteins in vasculitis lesions in patients with KD. Cytotoxic T cells may play a role in the development of vasculitis lesions in KD patients.

Orbital Epstein-Barr virus-related post-transplant lymphoproliferative disorder in a 13-year-old girl with cord blood transplantation.

Epstein-Barr virus-associated post-transplant lymphoproliferative disorder (EBV-PTLD) is increasingly recognized as a life-threatening complication after transplantation. Most areas affected by EBV-PTLD are lymph nodes, with occasional reports of extranodal lesions such as the gastrointestinal tract and central nervous system; however, orbital regions are extremely rare. We report a case of EBV-PTLD in a cord blood transplant recipient with a tumor in the upper right eyelid. Ultimately, eye symptoms were the first signs of PTLD. Transplant physicians should consider the possibility of PTLD when encountering an orbital lesion.

The ratio of CD163-positive macrophages to Iba1-positive macrophages is low in the intima in the early stage of cutaneous arteritis.

The etiology of polyarteritis nodosa (PAN) and localized PAN, including cutaneous arteritis (CA), remains unknown; however, initial endothelial damage has been implicated. The intima of the vasculitis lesions is predominantly infiltrated by innate-like bystander-activated CD8 T cells, in addition to the macrophages. Macrophages are among the major inflammatory cells involved in innate immunity and are classified into M1 and M2 subtypes. M1-type macrophages kill pathogens and cause inflammation, while M2-type macrophages promote the repair of tissues. Macrophage subtypes infiltrating in PAN and localized PAN vasculitis lesions have not yet been investigated. Innate immune response to a triggering factor on the endothelial cell surface may initiate CA pathogenesis. Thus, many M1-type macrophages may infiltrate in the intima during early CA. We assessed this hypothesis by immunohistochemical observation of macrophage phenotypes and polarization. Twenty-seven skin biopsy specimens from patients with CA were retrieved. Based on histology, we classified CA into four phases. The phenotypes of infiltrating macrophages in CA were evaluated by immunohistochemistry using antibodies against Iba-1, a pan-macrophage marker, and CD163, an M2-type macrophage marker. Our results showed that the ratio of CD163-positive M2-type macrophages to Iba1-positive macrophages was lower in the intima in the early stage of CA than in the later stage. In the media to adventitia, there was no significant difference in the ratios between these stages. These findings indicate that innate immunity is involved in the intima in the early stage of CA, suggesting that a trigger for CA might exist in endothelial cells.

An anaplastic pleomorphic xanthoastrocytoma with periventricular extension: An autopsy case report and review of the literature.

Pleomorphic xanthoastrocytomas (PXAs) are rare low-grade astrocytic tumors that typically present as superficial nodular cystic tumors of the cerebrum attached to the leptomeninx. Histologically, they are pleomorphic, hypercellular glial neoplasms. Despite the presence of microscopic pleomorphism, patients' postoperative prognosis is generally good. Anaplastic PXAs (APXAs) have a high mitotic index and patients with APXAs have a worse prognosis than patients with PXAs. Here, we report an autopsy case of APXA initially diagnosed as PXA. After gross total resection, the tumor recurred and was diagnosed as an APXA; thereafter, the patient died. An autopsy revealed that the tumor had relapsed at the primary site and had spread to the leptomeningeal space while concurrently invading the cerebrum including the periventricular area forming multifocal lesions. The histological findings of the autopsy were similar to those for epithelioid glioblastoma (EGBM) and small cell glioblastoma (SCGBM). In particular, the periventricular area with multifocal lesions was composed of SCGBM-like cells. It has been shown that multifocal lesions are frequently identified in patients with SCGBM. This is the first histopathologically confirmed case of APXA-related tumor presenting with periventricular extension and multifocal lesion formation. The periventricular extension might be a feature of PXAs and APXAs. However, suspected periventricular spread on imaging in past cases of PXAs and APXAs might instead represent the malignant transformation of these tumors to glioblastoma-like high-grade tumors, which often show SCGBM-like histological patterns.

Ultrastructure of CIC-DUX4 sarcoma: the first pathological report.

CIC-DUX4 sarcoma (CDS) is a recently identified subtype of small round cell sarcoma. Morphologically, CDS partially resembles Ewing sarcoma (ES) and has been classified as "ES-like sarcoma"; however, detailed clinicopathologic and molecular genetic analyses have indicated that CDS is a new independent disease. Many studies have provided light microscopic, immunohistochemical, and genetic information about CDS. However, ultrastructural findings associated with this sarcoma are lacking. The aim of this study was to investigate the ultrastructure of CDS tumors and to compare their features with those of ES. We examined two cytogenetically confirmed CDS cases. We found that, compared to typical ES, CDS presented heterogeneity: in cell density, from tightly packed to loosely unconnected areas; in cell shape, from polygonal to pleomorphic with small processes; and in nuclear shape including round, oval, polygonal, elongated, invaginated, or wrinkled formations. However, abundant glycogen in the cytoplasm and rare cell adhesion apparatus between cells are major similarities between CDS and typical ES. Neuroendocrine granules, which are seen in rare ES cases, could not be identified in these two CDS cases. Although cytogenetic differences can validate a definite diagnosis, ultrastructural features could also provide important information about the differences between CDS and ES.

Automated acquisition of explainable knowledge from unannotated histopathology images.

Deep learning algorithms have been successfully used in medical image classification. In the next stage, the technology of acquiring explainable knowledge from medical images is highly desired. Here we show that deep learning algorithm enables automated acquisition of explainable features from diagnostic annotation-free histopathology images. We compare the prediction accuracy of prostate cancer recurrence using our algorithm-generated features with that of diagnosis by expert pathologists using established criteria on 13,188 whole-mount pathology images consisting of over 86 billion image patches. Our method not only reveals findings established by humans but also features that have not been recognized, showing higher accuracy than human in prognostic prediction. Combining both our algorithm-generated features and human-established criteria predicts the recurrence more accurately than using either method alone. We confirm robustness of our method using external validation datasets including 2276 pathology images. This study opens up fields of machine learning analysis for discovering uncharted knowledge.

An autopsy case of widespread brain dissemination of glioblastoma unnoticed by magnetic resonance imaging after treatment with bevacizumab.

BACKGROUND: Although glioblastoma has been shown to be able to disseminate widely in the intracranially after treatment with bevacizumab without any significant radiological findings, reports on such cases with subsequent autopsy findings are lacking. CASE DESCRIPTION: A 36-year-old man presented with a general seizure and a mass of the right frontal lobe, which was diagnosed as diffuse astrocytoma (WHO Grade II). The patient underwent a total of four surgeries from 2005 to 2017. He showed tumor recurrence, progression, and malignant transformation to glioblastoma (GBM) (WHO Grade IV) despite repeated tumor resections, radiotherapy, and chemotherapies with temozolomide and carmustine wafers. Bevacizumab (10 mg/kg body weight) was started following the fourth surgery. After bevacizumab administration, the patient's clinical condition improved to a Karnofsky performance status (KPS) score of 50-60, and he was stable for several months before finally deteriorating and passing away. Although sequential magnetic resonance imaging (MRI) showed shrinkage of the lesion and a reduction of edema, an autopsy showed widespread tumor invasion that was not revealed on MRI. Neoplastic foci were identified extensively in the cerebral cortex, basal ganglia, pituitary gland, cerebellum, and brainstem, imposing as gliomatosis cerebri. CONCLUSION: Imaging follow-up of malignant gliomas needs to be interpreted with caution as marked improvement in radiological response after bevacizumab treatment may not be indicating tumor regression. Despite the notable lack of evidence to increase overall survival in GBM patients with bevacizumab, the increase in progression-free survival and the observed relief of symptoms due to a decrease in edema should be considered relevant for patient management.

Malignant peritoneal mesothelioma diagnosed 50 years post-radiotherapy for ovarian cancer in a patient with a history of multiple malignancies: An autopsy case.

As the number of long-term cancer survivors is increasing, the incidence of post-irradiation malignant mesothelioma may also increase. We herein present the case of an 85-year-old female patient with a history of several surgeries for solid tumors and radiotherapy to the pelvis, who presented with abdominal pain and diarrhea. The patient's general condition gradually worsened and she succumbed to cardiopulmonary arrest triggered by vomiting ~3 months after the onset of the abdominal symptoms. An autopsy revealed malignant intestinal obstruction caused by peritoneal mesothelioma. Irradiation is a known risk factor for malignant mesothelioma, which may develop ~10-30 years after radiotherapy. To the best of our knowledge, this is the first report of a patient with malignant mesothelioma developing ~50 years after radiotherapy. The aim of the present study was to remind physicians that malignant mesothelioma should be considered in the differential diagnosis of patients with a history of radiotherapy who present with gastrointestinal symptoms.

A fulminant case of classical Hodgkin lymphoma: A diagnostic dilemma of Epstein-Barr virus-positive large B-cell neoplasms.

We report a fulminant case of classical Hodgkin lymphoma (CHL). The patient died only approximately 2 months after the onset of subjective symptoms. Autopsy specimens revealed atypical cells resembling Hodgkin and Reed-Sternberg (HRS) cells in a rich inflammatory background in various organs. There were marked, characteristic angiodestructive lesions from infiltrating HRS-like cells and numerous macrophages. The HRS-like cells were infected with Epstein-Barr virus (EBV), immunohistochemically positive for PAX5 and CD30, and negative for CD3, CD20, and ALK. Most B-cell markers other than PAX5 were negative, and the HRS-like cells also expressed cytotoxic molecules. Monoclonal rearrangement of immunoglobulin heavy chain was detected by PCR analysis. According to the 2016 WHO classification, we diagnosed mixed cellularity CHL. However, EBV-positive diffuse large B-cell lymphoma (DLBCL), not otherwise specified and EBV-positive B-cell lymphoma, unclassifiable with features intermediate between DLBCL and CHL were considered as differential diagnoses because both tumors are aggressive EBV-positive large B-cell neoplasms with reactive inflammatory cells and sometimes contains HRS-like cells. The clinical condition of the current case was closer to these two entities than to CHL. A diagnosis of EBV-positive large B-cell neoplasms was difficult because of overlapping morphological and immunohistochemical characteristics, but should be considered for prognosis.

Effects of Morinda citrifolia on Rheumatoid Arthritis in SKG Mice.

Morinda citrifolia L., known as noni, originated from Indonesia exhibits various pharmacological activities including anti-inflammatory properties. However, the validity of noni fruit juice as a treatment for rheumatoid arthritis (RA), an autoimmune disorder, has not been confirmed yet. Therefore, the main purpose of this research was to evaluate the efficacy of noni fruit juice (INFJ) made in Indonesia using SKG mice as an animal model of RA, which shows the resembling characteristics of human RA patients. Furthermore, the safety of INFJ was examined by repeated dose experiments in mice. INFJ was mixed with water at 50% and administered to SKG mice sensitized with mannan, free access for 4 weeks. Arthritis scores of fore- and hind-leg joints were measured and the joints were histopathologically examined. The sub-acute and sub-chronic toxicities of INFJ were evaluated using BALB/c mice. The arthritic scores were significantly lower from the 7 d after sensitization in the INFJ group than the control group. Histopathological examinations of the joints revealed inhibition of severity of RA. In both toxicity studies, INFJ did not show any toxicities. INFJ exhibited anti-arthritic activity in arthritic and histopathological examinations of the joints in SKG mice. Present study was the first report where noni juice may be effective against RA. The dose of noni juice showing efficacy against RA was confirmed safe from repeated dose studies in mice.

Cell biological profiling of reprogrammed cancer stem cell-like colon cancer cells maintained in culture.

Cancer stem cells (CSCs) are specific targets for therapeutic applications, but the rarity of CSCs within tumors makes the isolation of CSCs difficult. To overcome these problems, we generated CSCs in vitro using established reprogramming techniques. We transduced four previously established reprogramming factors, Oct3/4, Sox2, Klf4, and L-myc, into the colon cancer cell lines LoVo and OUMS-23, and investigated the biological characteristics of these lines. Tra-1-60+ cells were obtained from reprogrammed induced pluripotent stem (iPS) cell-like colonies and showed CSC properties, including colony formation, maintenance of colonies by repeated passages, and feeder cell dependency, as well as increased expressions of CSC markers such as CD133 and ALDH1. The CSC-like cells showed increased chemoresistance to 5-fluorouracil and elevated tumorigenicity upon transplantation into kidneys of immune-deficient mice. These tumors shifted to a poorly differentiated stage with many atypical cells, cytoplasmic mucin, and focal papillary components, with demonstrated dedifferentiation. The principal component analysis from DNA microarrays showed that though both cell lines moved to iPS cells after reprogramming, they were not completely identical to iPS cells. Significantly elevated gene expression of Decorin and CD90 was observed in CSC-like cells. Together, these results show that reprogramming of cancer cells produced not pluripotent stem cells but CSC-like cells, and these findings will provide biological information about genuine CSCs and help establish new CSC-targeted therapies.