Chronic active myocarditis with spatially and temporally heterogeneous lesions causing severe heart failure and intractable atrial arrhythmia: An autopsy case report.

The pathogenesis of chronic active myocarditis remains unclear. A 65-year-old man underwent permanent pacemaker implantation for sick sinus syndrome and pulmonary vein isolation for paroxysmal atrial fibrillation. Four years later, the left ventricular ejection fraction decreased from 51 % to 35 %, and the apical left ventricular inferior wall developed akinesis. Isolated cardiac sarcoidosis was suspected; however, prednisolone and optimal medical therapy failed to improve the symptoms. Even after cardiac resynchronization therapy followed by atrioventricular junction ablation for untreatable atrial tachycardia, the patient died of heart failure eight years after referral. An autopsy revealed inflammatory cell infiltration accompanied by cardiac myocytolysis in both atria and ventricles. He was diagnosed with chronic active myocarditis based on pathological findings and a persistent increase in the blood high-sensitivity cardiac troponin levels before death. The myocardium around the sinus node showed extensive and severe fibrosis with mild inflammation, suggesting a chronic inflammatory phase. In contrast, the left atrium and both ventricles showed active myocardial inflammation with fibrosis, suggesting a persistently active inflammatory phase. This case demonstrated that atrial inflammation caused intractable atrial arrhythmia, while ventricular inflammation led to biventricular heart failure, and highlighted the presence of spatially and temporally heterogeneous inflammation in chronic active myocarditis. Learning objective: We describe a case of chronic active myocarditis with spatially and temporally heterogeneous lesions throughout the four cardiac chambers. Inflammatory cell infiltration was observed in both atria and ventricles. Extensive fibrosis replaced the myocardium around the sinus node, suggesting a chronic phase. The left atrium and ventricles showed active inflammation, suggesting an active phase. Atrial and ventricular inflammation led to atrial arrhythmia and heart failure, respectively.

Complete remission of giant cell myocarditis by prednisolone monotherapy: A case with mild inflammation demonstrated by mismatch between T2-high intensity areas and late gadolinium enhancement.

Giant cell myocarditis (GCM) is a potentially lethal subtype of myocarditis. Herein, we report a case of a 22-year-old woman with GCM who was successfully treated with prednisolone monotherapy. The patient had a fever and shortness of breath and was referred to our hospital. Laboratory test results revealed elevated troponin I levels. Cardiac magnetic resonance (CMR) showed high intensity in the inferoseptal segment of the left ventricle on T2-weighted short tau inversion recovery imaging without late gadolinium enhancement (LGE), suggesting predominant edema rather than necrosis. The patient was diagnosed with GCM based on an endomyocardial biopsy, which revealed lymphocyte infiltration and multinucleated giant cells in the absence of granuloma formation. Subsequently, the patient received intravenous methylprednisolone at 1000 mg/day for 3 days followed by oral prednisolone at 30 mg/day, which normalized troponin levels. Follow-up CMR revealed improved cardiac inflammation; therefore, the patient was discharged without prescribing another immunosuppressive agent. Prednisolone was tapered and terminated three years after discharge. The patient went one year without medication and had no recurrence of GCM on follow-up. This case highlights the presence of mild GCM, successfully treated by steroid monotherapy, in which the mismatch between high-intensity T2 areas and LGE suggests mild inflammation. Learning objective: Giant cell myocarditis (GCM) is potentially lethal and usually requires multiple immunosuppressive agents. Here, we report a patient with GCM with preserved left ventricular ejection fraction. Cardiac magnetic resonance revealed focal high T2 signal intensity areas without late gadolinium enhancement, indicating myocardial edema without necrosis. The patient remained in remission with prednisolone monotherapy for 2 years. Our report indicates that "mild" GCM may be treated with prednisolone monotherapy.

Follicular dendritic cell sarcoma arising from the lymph node of the pancreatic head: a case report with literature review.

A 72-year-old man was referred to our hospital for the examination of a pancreatic head mass. Abdominal computed tomography revealed a contrasted 8-cm-diameter tumor extending from the dorsal pancreatic head to the porta hepatis. The preoperative diagnosis was challenging due to the absence of specific imaging findings and the inability to perform a biopsy. Positron emission tomography/computed tomography and diffusion-weighted imaging suggested a malignant tumor originating from the organs surrounding the pancreatic head. Subtotal stomach-preserving pancreaticoduodenectomy with regional lymph node dissection was performed, as dissection from the pancreatic head proved unfeasible. Pathological examination identified the tumor as an enlarged lymph node consisting of pleomorphic large cells forming clusters, positive for follicular dendritic cell markers cluster of differentiation (CD) 21 and CD23. No evidence of tumor capsule infiltration, other organ infiltration, or metastasis to other lymph nodes was observed. The final diagnosis was nodal follicular dendritic cell sarcoma (FDCS) originating from the pancreatic head lymph nodes. No recurrence occurred at 3 years postoperatively with no postoperative treatment. Intraperitoneal nodal FDCS is extremely rare, and occasionally, it can lead to postoperative recurrence and progression. It is crucial to differentiate neoplastic lymph node enlargement around the pancreatic head from nodal FDCS.

Exploration of Malignant Characteristics in Neoadjuvant Chemotherapy-Resistant Rectal Cancer, Focusing on Extramural Lesions.

BACKGROUND: Extramural vascular invasion (EMVI) and tumor deposits (TD) are poor prognostic factors in rectal cancer (RC), especially when resistant to neoadjuvant chemotherapy (NAC). We aimed to define differential expression in NAC responders and non-responders with concomitant EMVI and TD. METHODS: From 52 RC surgical patients, post-NAC resected specimens were extracted, comprising two groups: cases with residual EMVI and TD (NAC-resistant) and cases without (NAC-effective). Proteomic analysis was conducted to define differential protein expression in the two groups. To validate the findings, immunohistochemistry was performed in another cohort that included 58 RC surgical patients. Based on the findings, chemosensitivity and prognosis were compared. RESULTS: The NAC-resistant group was associated with a lower 3-year disease-free survival rate than the NAC-effective group (p = 0.041). Discriminative proteins in the NAC-resistant group were highly associated with the sulfur metabolism pathway. Among these pathway constituents, selenium-binding protein 1 (SELENBP1) expression in the NAC-resistant group decreased to less than one-third of that of the NAC-effective group. Immunohistochemistry in another RC cohort consistently validated the relationship between decreased SELENBP1 and poorer NAC sensitivity, in both pre-NAC biopsy and post-NAC surgery specimens. Furthermore, decrease in SELENBP1 was associated with a lower 3-year disease-free survival rate (p = 0.047). CONCLUSIONS: We defined one of the differentially expressed proteins in NAC responders and non-responders, concomitant with EMVI and TD. SELENBP1 was suspected to contribute to NAC resistance and poor prognosis in RC.

Three-dimensional analysis of perineural invasion in extrahepatic cholangiocarcinoma using tissue clearing.

Perineural invasion (PNI) is a characteristic invasion pattern of distal cholangiocarcinoma (DCC). Conventional histopathologic examination is a challenging approach to analyze the spatial relationship between cancer and neural tissue in full-thickness bile duct specimens. Therefore, we used a tissue clearing method to examine PNI in DCC with three-dimensional (3D) structural analysis. The immunolabeling-enabled 3D imaging of solvent-cleared organs method was performed to examine 20 DCC specimens from five patients and 8 non-neoplastic bile duct specimens from two controls. The bile duct epithelium and neural tissue were labeled with CK19 and S100 antibodies, respectively. Two-dimensional hematoxylin/eosin staining revealed only PNI around thick nerve fibers in the deep layer of the bile duct, whereas PNI was not identified in the superficial layer. 3D analysis revealed that the parts of DCC closer to the mucosa exhibited more nerves than the normal bile duct. The nerve fibers were continuously branched and connected with thick nerve fibers in the deep layer of the bile duct. DCC formed a tubular structure invading from the epithelium and extending around thin nerve fibers in the superficial layer. DCC exhibited continuous infiltration around the thick nerve fibers in the deep layer. This is the first study using a tissue clearing method to examine the PNI of DCC, providing new insights into the underlying mechanisms.

18F­fluorodeoxyglucose positron emission tomography predicts recurrence and histological grade of extrahepatic bile duct cancer.

Malignant tumors in cholangiocarcinoma are diagnosed and staged using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and clinical analysis. However, comprehensive analysis, including pathological analysis, has not yet been sufficiently performed. In the present study, the maximum standardized uptake value (SUVmax) was calculated using FDG-PET and its relationship with clinicopathological factors was analyzed. The present study included 86 patients who underwent preoperative FDG-PET/computed tomography (CT) and did not receive chemotherapy among 331 patients with hilar and distal cholangiocarcinoma. Receiver operating characteristic analysis with recurrence events was used to determine the SUVmax cutoff of 4.9. Immunohistochemical staining of glucose transporter 1 (Glut1), hypoxia-inducible factor-1α and Ki-67 was performed for pathological analysis. The standardized uptake value (SUV)-high group (SUVmax ≥4.9) had a higher postoperative recurrence rate (P<0.046) and higher Glut1 and Ki-67 expression rates (P<0.05 and P<0.0001, respectively). Furthermore, SUVmax and Glut1 expression (r=0.298; P<0.01) and SUVmax and Ki-67 expression rates (r=0.527; P<0.0001) were positively correlated. The preoperative measurement of SUVmax by PET-CT is useful in predicting recurrence as well as cancer malignancy.

Use of time­density curves of dynamic contrast­enhanced computed tomography for determination of the histological therapeutic effects of neoadjuvant chemotherapy for pancreatic ductal adenocarcinoma.

The present study aimed to investigate the histological changes caused by neoadjuvant chemotherapy (NAC) for pancreatic ductal adenocarcinoma (PDAC), and to demonstrate the use of time­density curves (TDCs) of dynamic contrast­enhanced computed tomography (CECT) for determination of the histological therapeutic effects of NAC for PDAC. A total of 96 patients with PDAC were examined; 46 underwent NAC (NAC group) and 50 did not undergo NAC (non­NAC group). Based on histological therapeutic effect and using the area of residual tumor (ART) grading system, the NAC group was divided into low­responders and high­responders. Histological analysis was used to evaluate the densities of cancer cells, cancer­associated fibroblasts (CAFs), microvessels and stromal collagen fibers in the NAC and non­NAC groups. Radiological analysis was used to evaluate the TDCs of three slopes of the NAC group, namely slopes between the non­contrast and arterial phases (δ1 and δ1'), between the arterial and portal phases (δ2 and δ2'), and between the portal and equilibrium phases (δ3 and δ3'). δ1­Î´3 were before NAC, whereas δ1'­Î´3' were after NAC. Changes in δ1, δ2 and δ3 before and after NAC were denoted as δδ1 (=δ1'­Î´1), δδ2 (=δ2'­Î´2) and δδ3 (=δ3'­Î´3). ART grading system, histological examination and radiological examination data were also statistically analyzed. Histological examination revealed a significant decrease in cancer cells and CAFs, and a significant increase in stromal collagen fibers due to NAC (P<0.01). Radiological examination revealed that δ1' was significantly higher than δ1 in low­responders (P<0.05), whereas δ2' was significantly lower than δ2 in high­responders (P<0.01). δδ2 was significantly lower and δδ3 was significantly higher in high­responders than in low­responders (P<0.01 and P<0.05, respectively). Receiver operating characteristic curve showed that δδ2 and δδ3 were effective indicators of the histological therapeutic effect of NAC. In conclusion, the TDC of dynamic CECT may be useful for determining the histological therapeutic effect of NAC for PDAC.

Case Report: A Giant Epignathus with a Well-Developed Skeleton of Head and Neck.

Epignathus is an extremely rare teratoma found in the oral cavity or oropharyngeal region of newborns, whose pathogenesis is poorly understood. We describe a giant epignathus arising from the oropharynx in a newborn. The giant tumor completely obstructed the airway of the newborn resulting in death. Histological and radiological examination of the tumor reveals the presence of a remarkably well-developed skeleton of the head and neck. A row of teeth, the axis and atlas, thyroid and salivary glands, trachea, and cerebral tissue are all detected within the tumor. These findings suggest that the epignathus is fetus-in-fetu which is considered a type 0 germ cell tumor in accordance with current literature.

Acute Exacerbation of Interstitial Lung Disease After SARS-CoV-2 Vaccination: A Case Series.

CASE PRESENTATION: An acute exacerbation of interstitial lung disease (ILD) is an acute deterioration that can occur at any time and is associated with significant morbidity and mortality rates. We herein report three patients with ILD who experienced acute respiratory failure after SARS-CoV-2 messenger RNA vaccination. All the patients were male; the mean age was 77 years. They had a smoking history that ranged from 10 to 30 pack-years. Duration from the vaccination to the onset of respiratory failure was 1 day in two patients and 9 days in one patient. In an autopsied case, lung pathologic evidence indicated diffuse alveolar damage superimposed on usual interstitial pneumonia. In the other two cases, CT scans showed diffuse ground-glass opacities and subpleural reticulation, which suggests acute exacerbation of ILD. Two patients were treated successfully with high-dose methylprednisolone. Although benefits of vaccination outweigh the risks associated with uncommon adverse events, patients with chronic lung diseases should be observed carefully after SARS-CoV-2 vaccination.

Fragment-Based Discovery of a Novel, Brain Penetrant, Orally Active HDAC2 Inhibitor.

Fragment-based ligand discovery was successfully applied to histone deacetylase HDAC2. In addition to the anticipated hydroxamic acid- and benzamide-based fragment screening hits, a low affinity (∼1 mM) α-amino-amide zinc binding fragment was identified, as well as fragments binding to other regions of the catalytic site. This alternative zinc-binding fragment was further optimized, guided by the structural information from protein-ligand complex X-ray structures, into a sub-µM, brain penetrant, HDAC2 inhibitor (17) capable of modulating histone acetylation levels in vivo.

An autopsy case of amyotrophic lateral sclerosis with striatonigral and pallidoluysian degeneration and cat's-eye-shaped neuronal nuclear inclusions.

We report the case of a Japanese woman with sporadic amyotrophic lateral sclerosis (ALS) of 28 months' duration who died at the age of 66 years. Postmortem examination revealed moderate loss of neurons and phosphorylated TDP-43 (p-TDP-43)-immunoreactive neuronal and glial cytoplasmic inclusions in the upper and lower motor neurons. Additionally, marked neuronal loss was observed in the neostriatum, globus pallidum, subthalamic nucleus, and substantia nigra. p-TDP-43-immunoreactive inclusions were frequently found in these areas. Neuronal loss and TDP-43 pathology in the motor, striatonigral, and pallidoluysian systems were predominant on the right side. Moreover, p-TDP-43-immunoreactive cat's-eye-shaped neuronal nuclear inclusions (NNIs) were observed in the affected lesions. NNIs in the striatonigral system were also positive for valosin-containing protein (VCP). We diagnosed the patient as having ALS with striatonigral and pallidoluysian degeneration. Patients with ALS rarely experience pallido-nigro-luysian degeneration. To our best knowledge, only one case of ALS combined with striatonigral and pallidoluysian degeneration has been reported. Neuronal loss in the striatonigral and/or pallidoluysian systems has also been reported in patients with ALS with multisystem degeneration accompanied by long-term use of an artificial respirator. Based on these findings, a possibility of an extremely rare subtype of ALS demonstrating selective loss of neurons in the striatonigral and pallidoluysian systems exists; another possibility is that this type could be an early stage or forme fruste of ALS with multisystem degeneration. Although VCP-positive cat's-eye-shaped NNIs have been reported in spinocerebellar ataxia type-2 cases, our case report presents VCP-positive NNIs in a patient with ALS for the first time.

Heterogeneity of metabolic adaptive capacity affects the prognosis among pancreatic ductal adenocarcinomas.

BACKGROUND: Evolutionary cancer has a supply mechanism to satisfy higher energy demands even in poor-nutrient conditions. Metabolic reprogramming is essential to supply sufficient energy. The relationship between metabolic reprogramming and the clinical course of pancreatic ductal adenocarcinoma (PDAC) remains unclear. We aimed to clarify the differences in metabolic status among PDAC patients. METHODS: We collected clinical data from 128 cases of resectable PDAC patients undergoing surgery. Sixty-three resected tissues, 15 tissues from the low carbohydrate antigen 19-9 (CA19-9), 38-100 U/mL, and high CA19-9, > 500 U/mL groups, and 33 non-tumor control parts, were subjected to tandem mass spectrometry workflow to systematically explore metabolic status. Clinical and proteomic data were compared on the most used PDAC biomarker, preoperative CA19-9 value. RESULTS: Higher CA19-9 levels were clearly associated with higher early recurrence (p < 0.001), decreased RFS (p < 0.001), and decreased DSS (p = 0.025). From proteomic analysis, we discovered that cancer evolution-related as well as various metabolism-related pathways were more notable in the high group. Using resected tissue immunohistochemical staining, we learned that high CA19-9 PDAC demonstrated aerobic glycolysis enhancement, yet no decrease in protein synthesis. We found a heterogeneity of various metabolic processes, including carbohydrates, proteins, amino acids, lipids, and nucleic acids, between the low and the high groups, suggesting differences in metabolic adaptive capacity. CONCLUSIONS: Our study found metabolic adaptation differences among PDAC cases, pertaining to both cancer evolution and the prognosis. CA19-9 can help estimate the metabolic adaptive capacity of energy supply for PDAC evolution.

The clinical and neuropathological picture of adult neuronal intranuclear inclusion disease with no radiological abnormality.

In typical adult neuronal intranuclear inclusion disease (NIID) with predilection for the basal ganglia or cerebral cortex, not only neurons but also glial cells harbor intranuclear inclusions. In addition, these inclusions are present in the peripheral autonomic nervous system, visceral organs and skin. In NIID cases with an expansion of GGC repeats in the 5'-untranslated region (5'-UTR) of the Notch 2 N-terminal like C (NOTCH2NLC) gene, these repeats are located in an upstream open reading frame (uN2C) and result in the production of a polyglycine-containing protein called uN2CpolyG. Typically, patients with adult NIID show high-intensity signals at the corticomedullary junction on diffusion-weighted brain magnetic resonance imaging. We report a case of adult NIID in a 78-year-old Japanese male, who suffered from mild, non-progressive tremor during life but showed no radiographic abnormalities suggestive of adult NIID. Pathologically, ubiquitin-, p62- and uN2CpolyG-positive neuronal intranuclear inclusions were particularly frequent in the hippocampal formation, but were also seen in the enteric plexuses, kidney and cardiac muscles. By contrast, glial intranuclear inclusions were barely evident in the affected regions. The present case also had an immunohistochemical profile differing from that of typical adult NIID. The findings in this case suggest that adult NIID can show clinical, radiographic and pathological heterogeneity.

Time density curve of dynamic contrast-enhanced computed tomography correlates with histological characteristics of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an infiltrative growth pattern with intense desmoplastic stroma comprised of cancer-associated fibroblasts (CAFs). Additionally, the histological characteristics are considered to play a vital role in the poor prognosis of PDAC. However, the density of cancer cells, degree of desmoplasia and vascular proliferation varies in individual cases. We hypothesized that preoperative radiological images would reflect histological characteristics, such as cancer cell density, CAF density and microvessel density. To clarify the association between the histological characteristics and radiological images of PDAC, the cancer cell density, CAF density and microvessel density from surgical specimens were measured with immunostaining, and the time density curve of dynamic contrast-enhanced computed tomography (CECT) was analyzed. Overall, the initial slope between non-enhanced and arterial phases was correlated with microvessel density, and the second slope between arterial and portal phases was correlated with CAF and cancer cell densities. In conclusion, the present study suggested the possibility of estimating cancer cell, CAF and microvessel densities using the TDC of dynamic CECT.

A case report of mucinous adenocarcinoma derived from intra-ampullary papillary-tubular neoplasm with a malignant course.

BACKGROUND: Intra-ampullary papillary-tubular neoplasm (IAPN) has been classified as a Vater papillary tumor. The prognosis of IAPN is generally relatively good. Here, we describe a patient with a mucinous adenocarcinoma cluster in the Vater papilla of IAPN origin. CLINICAL PRESENTATION: The patient was a 66-year-old man who was admitted to our hospital after a diagnosis of pancreatic head carcinoma based on a pancreatic duct dilatation found on abdominal ultrasound. CT showed a 40 mm lesion in the pancreatic head and expansion of the main pancreatic duct to a maximum diameter of 9 mm on the caudal side of the lesion. The extrahepatic bile duct had also expanded to a maximum diameter of 8 mm. PET/CT showed fluorodeoxyglucose (FDG) accumulation of SUVmax 6.02 that corresponded to the tumor in the pancreatic head, though it did not suggest distant metastasis. The patient was diagnosed with pancreatic head carcinoma T3 N0 M0 Stage IIA and underwent a pancreaticoduodenectomy. Pathology indicated that the tumor in the pancreatic head was a benign inflammatory lesion. On the other hand, the papillotubular tumor pervading the lumen in the duodenal papillary common channel met the criteria for IAPN, and a mucinous adenocarcinoma cluster found in the surrounding stroma suggested malignant transformation of IAPN. No metastasis to lymph nodes was demonstrated. With regard to the mucus phenotype of each lesion, the IAPN was MUC2 and MUC5AC positive, while the mucinous adenocarcinoma was MUC2-positive and MUC5AC-negative. In addition, CD10 was negative in both lesions, suggesting that mucus transformation from the gastric type to the intestinal type was a key element. A blood test 10 months after surgery showed increased CA19-9 (105 U/mL) and CEA (7.1 ng/mL). Abdominal CT showed multiple cystoid nodes in the liver, which were diagnosed as multiple liver metastases of mucinous adenocarcinoma transformed from the IAPN. CONCLUSIONS: We reported a case with IAPN that developed in the Vater papilla, which took an extremely malignant course. IAPN generally has a good prognosis, but it is important to understand that a malignant course may occur.

Multiorgan emboli due to an intraluminal thrombus from frozen elephant trunk.

The impact of kinking of the nonstented part of a frozen elephant trunk on the development of adverse effects is unclear. We report a case of an infected thrombus within the kinked nonstented portion of the frozen elephant trunk that resulted in multiorgan embolization. A 45-year-old man presented with a 1-month history of high-grade fever and fatigue. He had undergone emergent total arch replacement and frozen elephant trunk implantation for type A acute aortic dissection 7 years previously. Computed tomography showed an intraluminal thrombus within the kinked nonstented portion of the frozen elephant trunk. An autopsy also showed an intraluminal thrombus within the graft and diffuse microembolization in the abdominal organs. Therefore, in this case, kinking of the nonstented part of the frozen elephant trunk had resulted in an infected intraluminal thrombus, which subsequently caused multiorgan embolization.

Investigating the association between radiological images and the pathology of rectal cancer treated with neoadjuvant chemotherapy.

In patients with rectal cancer treated with neoadjuvant chemotherapy (NAC), differences are often observed between high and low radiological image reduction effects. It may be suggested that high radiological image reduction indicates a beneficial response to chemotherapy. However, the pathological investigation of the differences between high and low radiological cancer volume reduction cases remains limited. In the current study, a total of 50 patients with rectal cancer, treated with NAC, were examined. The approximate pathological primary cancer area and the radiological cancer volume reduction ratio were measured using CT and/or MRI imaging and the donut-shaped measurement method. Immunostaining of cytokeratin AE1/AE3 was performed to quantitatively measure the cancer cell mass in the largest section of rectal cancer. Cytokeratin AE1/AE3-stained area (P=0.04), mitosis (P=0.0027) and radiological donut-shaped images after NAC (P=0.010) were lower in the high radiological cancer volume reduction ratio group compared with the low radiological cancer volume reduction ratio group. These findings indicate that the radiological images had some ability to determine the treatment effect and clinicopathological characteristics of patients with rectal cancer treated with NAC.

A case of aortocolonic fistula caused by sigmoid diverticulitis.

The development of a secondary aortoenteric fistula is a well-described complication after open or endovascular repair of an abdominal aortic aneurysm. However, evidence regarding aortocolonic fistulas (ACFs) and their pathogenesis is currently limited. We present a case of ACF that developed 18 years after open repair of an abdominal aortic aneurysm with atypical symptoms. The patient was successfully treated with total resection of the involved aorta, prosthetic graft, and sigmoid colon, with extra-anatomic bypass and primary anastomosis of the residual colon. Pathologic examination revealed that the pathogenesis of ACF was attributed to sigmoid diverticulitis. This case report highlights the uncommon pathogenesis of ACF and the importance of considering revascularization and intestinal reconstruction in the surgical strategy for each individual case.

Plastic-scale-model assembly of ultrathin film MEMS piezoresistive strain sensor with conventional vacuum-suction chip mounter.

We developed a plastic-scale-model assembly of an ultrathin film piezoresistive microelectromechanical systems (MEMS) strain sensor with a conventional vacuum-suction chip mounter for the application to flexible and wearable strain sensors. A plastic-scale-model MEMS chip consists of 5-µm ultrathin piezoresistive strain sensor film, ultrathin disconnection parts, and a thick outer frame. The chip mounter applies pressure to the ultrathin piezoresistive strain sensor film and cuts the disconnection parts to separate the sensor film from the outer frame. The sensor film is then picked up and placed on the desired area of a flexible substrate. To cut off and pick up the sensor film in the same manner as with a plastic scale model, the design of the sensor film and disconnection parts of MEMS chips were optimized through numerical simulation and chip-mounting experiments. The success rate of the 5-µm ultrathin sensor film mounting increased by decreasing the number and width of the disconnection parts. For a 5-µm-thick 1 × 5 mm2 sensor film, 4 disconnection parts of 20 µm in width achieved 100% success rate. The fabricated ultrathin MEMS piezoresistive strain sensor exhibited a gauge factor of 100 and high flexibility to withstand 0.37 [1/mm] bending curvature. Our plastic-scale-model assembly with a conventional vacuum-suction chip mounter will contribute to more practical manufacturing of ultrathin MEMS sensors.