Isobutyric acid enhances the anti-tumour effect of anti-PD-1 antibody.

The low response rate of immune checkpoint inhibitors (ICIs) is a challenge. The efficacy of ICIs is influenced by the tumour microenvironment, which is controlled by the gut microbiota. In particular, intestinal bacteria and their metabolites, such as short chain fatty acids (SCFAs), are important regulators of cancer immunity; however, our knowledge on the effects of individual SCFAs remains limited. Here, we show that isobutyric acid has the strongest effect among SCFAs on both immune activity and tumour growth. In vitro, cancer cell numbers were suppressed by approximately 75% in humans and mice compared with those in controls. Oral administration of isobutyric acid to carcinoma-bearing mice enhanced the effect of anti-PD-1 immunotherapy, reducing tumour volume by approximately 80% and 60% compared with those in the control group and anti-PD-1 antibody alone group, respectively. Taken together, these findings may support the development of novel cancer therapies that can improve the response rate to ICIs.

Investigating the early diagnosis of pancreatic cancer by surveillance of patients with "K-sign" of the pancreas by computed tomography: A prospective study.

BACKGROUND: We previously conducted a retrospective study investigating pancreatic morphological abnormalities that lead to early diagnosis of pancreatic cancer (PC) using computed tomography (CT). We reviewed 41 of 308 PC patients between 2011 and 2017 who had previously undergone CT to look for morphological changes leading to cancer development. In 24 patients (58.5%), a K-shaped constriction of the pancreas ("K-sign") was observed before the appearance of cancer. This study aimed to investigate whether an early PC diagnosis is possible by prospective CT follow-up of patients with the K-sign. METHODS: We investigated PC development through prospective surveillance of patients exhibiting K-signs identified on CT. RESULTS: Of approximately 87 000 CT scans performed between April 2019 and August 2022, the K-sign was observed in 54 patients. A total of 30 patients provided informed consent and were subsequently monitored using CT. Five patients (16.7%) were diagnosed with PC and underwent surgery after 3-24 months follow-up. Pathologically, four of five patients (80%) were diagnosed with early-stage pancreatic cancer (stage 0-IA). All patients exhibited defects in acinar structure, fibrous tissue, fat replacement, and inflammatory cells, suggesting their potential involvement in PC development. CONCLUSION: The detection and surveillance of the K-sign may be helpful for early PC diagnosis.

Remodeling of Lumbar Spinal Osteoid Osteoma Resected With Microscopic Surgery in a 15-Year-Old Basketball Player: A Case Report.

This case report focuses on a 15-year-old competitive-level high school basketball player who experienced chronic low back pain. Diagnostic imaging revealed osteoid osteoma in the L5 posterior element, causing osteosclerotic deformity of the left lamina and more inferior facet. To return him to the condition of sports activity, less invasive surgery of microscopic tumor resection with autologous bone grafting was planned instead of CT-guided ablation, which can cause thermal injury to nearby tissues. This procedure could preserve spinal structures, including the facet, pedicle, and paravertebral muscles. The day after surgery, the patient experienced a complete resolution of lower back pain. He gradually resumed light exercise two months postoperatively. Three-month follow-up CT imaging revealed bone remodeling at the resection site, to return to complete basketball activities. Over five years, no tumor recurrence or symptoms were observed, and he maintained his competitive activity level.

Life-threatening gastrointestinal bleeding caused by perforation of a penetrating atherosclerotic ulcer into the esophagus.

We present a case of life-threatening gastrointestinal bleeding caused by a penetrating atherosclerotic ulcer (PAU) that ruptured into the esophagus. A 65-year-old man presented with pyrexia and nausea. Contrast-enhanced computed tomography (CT) performed on admission revealed a hematoma between the lower esophagus and descending aorta due to a contained rupture of a PAU, which was undiagnosed at that time. Esophagogastroduodenoscopy (EGD) performed on the fifth day of admission revealed a subepithelial lesion in the lower esophagus, further complicated by ulcer formation. Biopsy did not reveal any malignant findings. On the eighth day of admission, the patient experienced substantial hematemesis with vital signs indicative of shock. Emergency EGD was performed, which revealed life-threatening bleeding in the lower esophagus. Contrast-enhanced CT revealed an aortoesophageal fistula with massive hematemesis, after which the patient died. An autopsy revealed perforation of the PAU into the esophagus without aortic dissection or a true aneurysm.Patients with atherosclerosis who develop recent-onset gastrointestinal symptoms, progressive anemia, and/or periaortic lesions should be carefully evaluated using contrast-enhanced CT, and PAU should be considered in the differential diagnosis.

Rac1 activation in oral squamous cell carcinoma as a predictive factor associated with lymph node metastasis.

OBJECTIVES: Secondary lymph node metastasis (SLNM) indicates a poor prognosis, and limiting it can improve the survival rate in early-stage tongue squamous cell carcinoma (TSCC). Many factors have been identified as predictors of SLNM; however, there is no unified view. Ras-related C3 botulinum toxin substrate 1 (Rac1) was found to be a promoter of the epithelial-mesenchymal transition (EMT) and is also attracting attention as a new therapeutic target. This study aims to investigate the role of Rac1 in metastasis and its relationship with pathological findings in early-stage TSCC. MATERIALS AND METHODS: Rac1 expression levels of 69 cases of stage I/II TSCC specimens and their association with clinicopathological characteristics were evaluated by immunohistochemical staining. The role of Rac1 in oral squamous cell carcinoma (OSCC) was examined after Rac1 in OSCC cell lines was silenced in vitro. RESULTS: High Rac1 expression was significantly associated with the depth of invasion (DOI), tumor budding (TB), vascular invasion, and SLNM (p < 0.05). Univariate analyses revealed that Rac1 expression, DOI, and TB were factors significantly associated with SLNM (p < 0.05). Moreover, our multivariate analysis suggested that Rac1 expression was the only independent determinant of SLNM. An in vitro study revealed that Rac1 downregulation tended to decrease cell migration and proliferation. CONCLUSION: Rac1 was suggested to be an important factor in the metastasis of OSCC, and it could be useful as a predictor of SLNM.

Invasive breast cancer with complete infarct necrosis: Presentation of case.

INTRODUCTION AND IMPORTANCE: Infarction occurs occasionally in benign mammary tumors but is extremely rare in breast cancer, with few cases having been reported. PRESENTATION OF CASE: A 53-year-old woman presented to our hospital with a mass and pain in the upper lateral region of the right breast. She underwent a needle biopsy and was histologically diagnosed as having invasive carcinoma. A ring-enhancing spherical mass was seen on contrast-enhanced computed tomography and magnetic resonance images. She underwent a right partial mastectomy with sentinel lymph node biopsy for T2N0M0 breast cancer. Macroscopically, the tumor was a yellow mass. Histopathologically, the site contained extensively necrotic tissue with foam cell aggregation, lymphocytic infiltration, and fibrosis in the periphery. No viable tumor cells were observed. The patient was followed up without postoperative chemotherapy or radiotherapy. CLINICAL DISCUSSION: Ultrasound examination performed before the biopsy showed blood flow inside the tumor, but a review of the histopathological tissue after surgery revealed generally low viability of the tumor cells in the biopsy specimen, and the possibility that the tumor had a strong tendency to be necrotic from the beginning was considered. It is presumed that some immunological mechanism was working. CONCLUSION: We have encountered a case of breast cancer with complete infarct necrosis. Infarct necrosis may be present if a contrast-enhanced image shows ring-like contrast.

[Malignant Melanoma of a Male Breast That Was Difficult to Differentiate from Breast Cancer-A Case Report].

INTRODUCTION: Malignant melanoma in the male breast is extremely rare. Here we report a case of malignant melanoma in which a small cystic lesion in the male breast gradually increased during follow-up and was difficult to distinguish from breast cancer. CASE: A 65-year-old male was diagnosed with a tumor in the right breast and was referred to our department for further examination. At 42 years of age, he underwent tumor resection of a malignant melanoma of the abdominal skin. Mammary ultrasonography showed a 0.6 cm cystic mass in his right breast. Eight months later, the right breast mass had increased to 1.4 cm, and a core needle biopsy suggested breast cancer. Total mastectomy with axillary lymph node dissection was performed. HE staining of the resected tumor showed intranuclear inclusion bodies and some large nucleoli. On the basis of various immunostaining methods, malignant melanoma was diagnosed instead of breast cancer. After surgery, adjuvant chemotherapy with molecularly targeted drugs was administered. DISCUSSION: This might have been a case of male breast metastasis of malignant melanoma with very late recurrence.

A case of early gastric cancer resembling a subepithelial lesion diagnosed by endoscopic ultrasound-guided fine needle aspiration.

We present a case of early gastric cancer resembling a subepithelial lesion (GCSEL) derived from the submucosal ectopic gastric glands (SEGGs), diagnosed using endoscopic ultrasound-guided fine needle aspiration (EUS-FNA). A 55-year-old woman was referred to our hospital for the investigation of a subepithelial lesion (SEL). Contrast computed tomography and esophagogastroduodenoscopy revealed two SELs in the greater curvature of the fundus and the posterior wall of the upper body of the stomach. EUS revealed a hypoechoic lesion in the submucosa and suggested partial invasion into the muscularis propria of the greater curvature of the fundus, and an anechoic lesion in the submucosa of the posterior wall of the upper body. The different diagnosis for the SEL in the fundus was GCSEL, neuroendocrine tumor, malignant lymphoma, and gastric adenocarcinoma of fundic gland type. EUS-FNA findings suggested adenocarcinoma. The patient underwent a laparoscopic proximal gastrectomy. Pathological findings confirmed a differentiated tubular adenocarcinoma derived from the SEGG, which partially invaded into the submucosa of the surrounding gastric wall without lymphovascular invasion or lymph node metastasis. The patient has been recurrence-free after 10 months of follow-up. EUS should be performed for SELs followed by EUS-FNA for lesions, such as GCSEL, that require early intervention.

Laparoscopic Approach to Presacral Recurrence of Sacrococcygeal Teratoma.

A 6-month-old girl was presented to our hospital due to a presacral mass found 5 months after surgery of sacrococcygeal teratoma. The original tumor was a 63 x 50 mm sized round cyst connecting to the coccyx, observed with computed tomography. The initial operation was performed with en bloc removal of the tumor along with the coccyx in the prone position. During a routine follow up, ultrasonography indicated a possible local recurrence, 5 months after the initial operation. The magnetic resonance imaging revealed a polycystic formation with a diameter of 20 x 11 x 17 mm in the presacral space. The laparoscopic operation was conducted with the patient in the lithotomy and Trendelenburg position. The broad ligament of uterus was fixed to the abdominal skin and the rectum was mobilized to identify the tumor, which was resected laparoscopically. A histopathological examination showed the tumor to be a mature cystic teratoma. We observed her without any additional treatment and no recurrence is seen after 6 months.

DNA methylation profiles in the blood of newborn term infants born to mothers with obesity.

Maternal obesity is an important risk factor for childhood obesity and influences the prevalence of metabolic diseases in offspring. As childhood obesity is influenced by postnatal factors, it is critical to determine whether children born to women with obesity during pregnancy show alterations that are detectable at birth. Epigenetic mechanisms such as DNA methylation modifications have been proposed to mediate prenatal programming. We investigated DNA methylation signatures in male and female infants from mothers with a normal Body Mass Index (BMI 18.5-24.9 kg/m2) compared to mothers with obesity (BMI≥30 kg/m2). BMI was measured during the first prenatal visit from women recruited into the Ontario Birth Study (OBS) at Mount Sinai Hospital in Toronto, ON, Canada. DNA was extracted from neonatal dried blood spots collected from heel pricks obtained 24 hours after birth at term (total n = 40) from women with a normal BMI and women with obesity matched for parity, age, and neonatal sex. Reduced representation bisulfite sequencing was used to identify genomic loci associated with differentially methylated regions (DMRs) in CpG-dense regions most likely to influence gene regulation. DMRs were predominantly localized to intergenic regions and gene bodies, with only 9% of DMRs localized to promoter regions. Genes associated with DMRs were compared to those from a large publicly available cohort study, the Avon Longitudinal Study of Parents and Children (ALSPAC; total n = 859). Hypergeometric tests revealed a significant overlap in genes associated with DMRs in the OBS and ALSPAC cohorts. PTPRN2, a gene involved in insulin secretion, and MAD1L1, which plays a role in the cell cycle and tumor suppression, contained DMRs in males and females in both cohorts. In males, KEGG pathway analysis revealed significant overrepresentation of genes involved in endocytosis and pathways in cancer, including IGF1R, which was previously shown to respond to diet-induced metabolic stress in animal models and in lymphocytes in the context of childhood obesity. These preliminary findings are consistent with Developmental Origins of Health and Disease paradigm, which posits that adverse prenatal exposures set developmental health trajectories.

Recurrent malignant peripheral nerve sheath tumor presenting as an asymptomatic intravenous thrombus extending to the heart: a case report.

BACKGROUND: Malignant peripheral nerve sheath tumor (MPNST) is a rare soft tissue sarcoma mainly treated via surgical resection. Herein, we report a case of MPNST wherein a massive tumor thrombus extended to the major veins and heart. CASE PRESENTATION: A 39-year-old female with a history of neurofibromatosis type 1 developed MPNST from the right radial nerve. In addition to adjuvant chemotherapy, she underwent wide tumor resection and concomitant radial nerve resection, followed by postoperative radiotherapy. Histological evaluation revealed marked venous invasion. The 2-year follow-up CT revealed an asymptomatic recurrent tumor thrombus extending from the right subclavian vein to the heart. An urgent life-saving operation was performed to ligate the base of the right subclavian vein and remove the entire intravenous thrombus that extended to the right ventricle. The remaining tumor in the right subclavian vein increased in size 3 months after thrombectomy. After confirming the absence of any metastatic lesions, the patient underwent extended forequarter amputation to achieve surgical remission. One year later, a new metastasis to the right diaphragm was safely resected. The patient remains alive without any evidence of disease 2 years after the extended forequarter amputation. CONCLUSIONS: In cases of a previous history of microscopic venous invasion, recurrence can occur as a massive tumor thrombus that extends to the great vessels.

Non-small cell lung cancer with multiple brain metastases remains relapse-free for more than 13 years: A case report.

Brain metastasis (BM) in patients with non-small cell lung cancer (NSCLC) is usually associated with a poor prognosis. A 55-year-old Japanese man visited Tokyo Dental College Ichikawa General Hospital with complaints of motor aphasia and fatigue. Enhanced magnetic resonance imaging of the brain revealed multiple tumors. The patient's medical history included lung cancer surgery performed at another hospital 3 months prior to his visit to our hospital. Total resection of the left frontal tumor revealed BM from lung adenocarcinoma. Stereotactic radiosurgery (SRS) was performed for the remaining three BMs. At 9 months after SRS, another new BM was discovered, and SRS was again performed. More than 13 years have elapsed since the last SRS was performed, and the patient has remained relapse-free. To the best of our knowledge, this is the first case report describing a patient with NSCLC with multiple BMs who has remained relapse-free for >13 years with no neurological dysfunction, including cognitive deficit.

Dedifferentiated Osteosarcoma of the Distal Ulna: A Case Report.

Osteosarcoma is the most common malignant primary bone tumor that occurs most frequently in the second decade of life but rarely in patients over 40 years of age. The most common primary sites of osteosarcoma are the distal femur followed by proximal tibia and proximal humerus, and involvement of the wrist is extremely rare. Moreover, dedifferentiated osteosarcoma is also a rare condition that progresses to high-grade osteosarcoma from low-grade osteosarcoma, usually central low-grade osteosarcoma or parosteal osteosarcoma that bears MDM2 and/or CDK4 gene amplifications. We herein report an extremely rare case of dedifferentiated osteosarcoma arising in the distal ulna of an adult over 40 years of age. The patient was a 46-year-old man with a 2-month history of pain in his left swollen wrist. The initial radiological findings suggested a benign bone tumor in the distal ulna, and the lesion was marginally excised at the nearby hospital. Although the pathological diagnosis at the nearby hospital suggested a benign cartilaginous tumor, the tumor recurred in an aggressive manner 8 months after the initial surgery. The patient was referred to our hospital, and an incisional biopsy showed a high-grade osteosarcoma. The primary tumor was retrospectively re-evaluated at our hospital and diagnosed as low-grade osteosarcoma. Since neoadjuvant chemotherapy failed to shrink the tumor, the patient had to undergo below the elbow amputation to cure the disease. Although the tumor was negative for MDM2 nor CDK4, the definitive diagnosis of dedifferentiated osteosarcoma was made according to the clinical course and the histological findings. Lung metastases were found 10 months after the amputation, which were successfully treated by neoadjuvant chemotherapy and surgery. The patient has been doing well with no evidence of disease for 1 year and 6 months. Surprisingly, the literature review revealed that many low-grade osteosarcomas of the distal ulna progressed to high-grade dedifferentiated osteosarcomas. One should bear in mind that the diagnosis and treatment for bone-forming tumors of the distal ulna should be made very carefully because, although rare, it is possible that the tumor may initially appear as a benign or low-grade malignant tumor and may progress to high-grade osteosarcoma.

Low-grade osteosarcoma is predominant in gnathic osteosarcomas: A report of seven cases of osteosarcoma of the jaw.

OBJECTIVE: Primary osteosarcoma of the jaw bones is very rare, and histological features of gnathic osteosarcoma remain obscure. The purpose of this study was to describe the clinicopathological features of gnathic osteosarcoma. MATERIALS AND METHODS: Seven cases of gnathic osteosarcoma from Japan diagnosed during the period between 2000 and 2016 were examined retrospectively. The histology of the surgical pathology materials was reviewed by two pathologists. Clinical information was obtained from the hospital's information system. RESULTS: Of the seven cases, two patients had secondary osteosarcomas. As for the five cases of primary osteosarcoma, their ages ranged from 26 to 58 years (mean: 36.2, median: 28). Histologically, three cases were fibrotic tumors composed of spindle-shaped cells with mild to moderate nuclear atypia and the collagenous stroma accompanied by woven bones or mature lamellar-like bones. Two cases had cartilage formation. MDM2 and CDK4 expression was observed in two out of three cases on immunostaining. The histopathology of these three cases was regarded as the counterpart of low-grade osteosarcomas, namely, parosteal osteosarcoma and low-grade central osteosarcoma, arising in long bones. CONCLUSIONS: The surprisingly high incidence (60%, 3/5 cases) of low-grade osteosarcoma explains the reason why gnathic osteosarcomas present a more favorable prognosis than osteosarcomas arising in long bones. Furthermore, it provides insight into the tumorigenesis mechanism of low-grade osteosarcomas arising in the jaw and other sites.

Methotrexate-associated lymphoproliferative disorder of the thoracic spine in a patient with rheumatoid arthritis receiving methotrexate: a case report.

Methotrexate-associated lymphoproliferative disorder is recognized as a lymphoma that occurs following methotrexate administration. The lesion of the spine is extremely rare, and only one case of lesion in the lumbar spine has been reported so far. Here, we present a case of methotrexate-associated lymphoproliferative disorder of the thoracic spine in a 54-year-old woman with rheumatoid arthritis. The lesion formed an extra-skeletal tumor mass from lateral to the vertebral body to the paravertebral muscle extending posterior to the epidural space without bone destruction. Magnetic resonance imaging showed low signal intensities on both T1- and T2-weighted images and high signal intensity with short-tau inversion recovery. These radiological findings were similar to those for primary spinal lymphoma. The lesion rapidly paralyzed the patient, forcing her to be treated with posterior spinal decompression. The lesion could not be resected because it adhered to the dura. Following the histopathological diagnosis as methotrexate-associated lymphoproliferative disorder, methotrexate administration was terminated. The remaining mass lesion showed complete regression within 6 months. Methotrexate-associated lymphoproliferative disorder, which could be cured by the discontinuation of methotrexate, should be considered a differential diagnosis in spinal lesion cases showing lymphoma-like appearance with methotrexate treatment to avoid unnecessary treatments.

[Two Cases of Hereditary Breast Cancer in Which Genetic Counseling Was Useful].

INTRODUCTION: The importance of genetic counseling has been noted for hereditary breast cancer. We report the cases of two 32-year-old woman, unmarried, BRCA mutation-positive patients. CASES: In Case 1, the chief complaint was awareness of a right breast mass. There was a family history of breast cancer(3 previous cases in the family). The BRCA2 mutation was positive during the BRACAnalysis test. Right breast mastectomy and axillary dissection were performed. Genetic counseling was performed postoperatively, and her eggs were cryopreserved. In Case 2, the chief complaint was calcification of the right breast. She also had a family history of breast cancer(3 previous cases in the family). The BRCA1 mutation was positive during the BRACAnalysis test. Nipple-sparing mastectomy and sentinel lymph node biopsy were performed, and the pathological diagnosis was DCIS. After genetic counseling, she did not desire the cryopreservation of her eggs. DISCUSSION: In these cases, the histological type, stage, subtype, BRCA mutation site, etc., were different from each other, and detailed support by genetic counseling was taken according to each medical condition such as surgery and postoperative adjuvant therapy.

[Surgical Resection of Pulmonary Metastases from Gastric Cancer;Report of a Case].

Lung metastasis of gastric cancer often presents as multiple pulmonary metastases or cancerous lymphadenopathy, which is rarely indicated for surgery and has a poor prognosis. We report a case of solitary metastases that were surgically resected. The patient underwent distal gastrectomy for stomach cancer and then received chemotherapy for abdominal lymph node metastasis. However, he developed pulmonary metastases in the right S6 and S8, and thus underwent right S6 resection and partial resection 29 and 41 months after the gastrectomy, respectively. The pathological diagnosis was gastric cancer metastases. After undergoing surgery for resection of the metastases, he developed new metastases in abdominal lymph nodes and died 5 years after the 1st surgery.

[Chronic active Epstein-Barr virus infection with multiple vascular lesions successfully treated by cord blood transplantation].

An 18-year-old woman presented with fever and liver dysfunction. Computed tomography showed lymphadenopathy, hepatosplenomegaly, and vascular lesions such as aneurysms and irregularities at multiple arteries, including coronary arteries. Based on the high copy number of Epstein-Barr virus (EBV)-DNA in the peripheral blood, EBV-infected CD4+T cells, and the proliferation of EBER-positive cells in the bone marrow, chronic active EBV infection (CAEBV) was diagnosed. Although the fever and liver dysfunction improved as a result of the initial immunosuppressive therapy and multiagent chemotherapy, EBV-DNA remained high. Moreover, she experienced repeated episodes of angina pectoris due to coronary arterial lesions. Therefore, cord blood transplantation was performed after reduced-intensity conditioning. EBV-DNA decreased quickly after initiating the conditioning and became undetectable at day 7 after the transplant. Vascular lesions did not progress after the transplant, and the patient's angina pectoris resolved. At 2.5 years after the transplant, she is alive without disease recurrence. The prognosis of CAEBV with vascular lesions is especially poor. Although the indication for allogeneic hematopoietic stem cell transplantation (HSCT) is difficult to determine in such cases, the clinical course of our case suggests that allogenic HSCT could be safely performed under appropriate management and could successfully control not only CAEBV but also vascular lesions.

IgG4-related pleural disease in a patient with pulmonary adenocarcinoma under durvalumab treatment: a case report.

BACKGROUND: Immune checkpoint inhibitors (ICIs) are the standard treatment for non-small cell lung cancer. The unique adverse events that can arise after treatment with ICIs are known as immune-related adverse events (irAE). As the number of cases under treatment with ICIs increases, new types of characteristics of irAE have emerged. This case report suggests that IgG4-related pleural disease could occur as an irAE. CASE PRESENTATION: A 64-year-old man was diagnosed with pulmonary adenocarcinoma stage IIIB. Following concurrent chemoradiotherapy, durvalumab was administered every two weeks. The patient complained of dyspnea on effort 4 months after the initiation of durvalumab therapy. Chest CT scans showed mild bilateral pleural effusion 4 months after the initiation of durvalumab therapy, and the amount of pleural effusion increased further at 7 months. Durvalumab was thought to be a potential cause of pleural effusion and was withdrawn after 13 courses of administration over 7 months. The level of serum IgG4 was 2750 mg/dL. The levels of IgG4 of the pleural fluids were 2790 mg/dL on the right side and 2890 mg/dL on the left side at 7 months. Microscopic examination of the pleural biopsy revealed lymphoplasmacytic infiltration with storiform fibrosis. Immunohistochemical examinations showed that the number of IgG4-positive cells was > 20/high power field and the percentage of IgG4-positive to IgG-positive plasma cells was > 50%. Oral prednisolone at a dose of 30 mg/day was initiated, and remarkable clinical improvements were achieved. After 4 months of prednisolone therapy, the level of serum IgG4 decreased to 370 mg/dL and chest CT revealed the disappearance of bilateral pleural effusion. CONCLUSION: This was a case of IgG4-related pleural disease in a patient with pulmonary adenocarcinoma under durvalumab treatment. To our knowledge, this is the first case report of IgG4-related pleural disease as an irAE. It is important to consider the possibility of IgG4-related pleural disease in cases of pleural effusion during the treatment with ICIs.