Magnetic Resonance Imaging Features for Differentiating Low-Grade and High-Grade Malignant Peripheral Nerve Sheath Tumors.

OBJECTIVE: This study aimed to assess the usefulness of magnetic resonance imaging (MRI) findings for differentiating low-grade and high-grade malignant peripheral nerve sheath tumors (MPNSTs). METHODS: This study included 31 patients (onset age range, 19-83 years; mean onset age, 57 years; 9 men and 22 women) with 36 histopathologically proven MPNSTs (7 low-grade MPNSTs and 29 high-grade MPNSTs) who underwent preoperative MRI between December 2007 and October 2022. Quantitative and qualitative MRI findings were retrospectively evaluated and compared between the 2 subtypes. RESULTS: The maximum tumor diameter (106.1 ± 64.0 vs 54.9 ± 19.8 mm, P = 0.032) and tumor-to-muscle signal intensity ratio (SIR) of fat-suppressed gadolinium-enhanced T1-weighted images (2.69 ± 1.40 vs 1.62 ± 0.40, P = 0.005) were significantly higher in high-grade MPNSTs than in low-grade MPNSTs. The receiver operating characteristic analysis revealed that the tumor-to-muscle SIR of fat-suppressed gadolinium-enhanced T1-weighted images exhibited the highest area under the curve value (0.88), followed by the maximum tumor diameter (0.76). The sensitivity and specificity of the tumor-to-muscle SIR of fat-suppressed gadolinium-enhanced T1-weighted images for diagnosing high-grade MPNST at an optimal SIR threshold of greater than 1.73 were 90% and 83%, respectively. However, other MRI findings showed no significant differences between the 2 subtypes (P = 0.16-1.00). CONCLUSIONS: Although the MRI findings of low-grade and high-grade MPNST overlapped considerably, the maximum tumor diameter and degree of contrast enhancement can be used to differentiate low-grade MPNST from high-grade MPNST.

Poorly Differentiated Chordoma of the Clivus With Loss of SMARCB1 Expression in a Pediatric Patient: A Case Report.

Poorly differentiated chordoma (PDC) is a rare, aggressive subtype of chordoma. A two-year-old girl presented with cervical pain, limb paralysis and respiratory failure. Magnetic resonance imaging and positron emission tomography-computed tomography revealed a tumor compressing the pons at the clivus and osteoblastic metastatic lesions of the left upper arm and right iliac bone. Her tumors shrank substantially after treatment with chemotherapy and proton beam therapy. Our initial diagnosis was an atypical teratoma/rhabdoid tumor, but final diagnosis of PDC was made on the basis of the immunohistochemical expression of brachyury. In addition, the detection of SMARCB1/INI1 mutation confirmed the diagnosis of PDC.

A somatic activating KRAS variant identified in an affected lesion of a patient with Gorham-Stout disease.

Gorham-Stout disease (GSD), a rare disorder of unknown etiology, is characterized by massive osteolysis that is associated with proliferation and dilation of lymphatic vessels. Variants in cancer-associated genes have been described in complex lymphatic anomalies. To explore the pathogenesis of GSD, we performed the amplicon-based deep sequencing on 50 cancer-related genes to assay affected tissues from the six patients with GSD. In one patient, a somatic activating KRAS c.182A > G variant (p.Q61R) was detected in 1% of the tissue sample. Conversely, the mutant allele was not detected in uninvolved normal skin and blood samples. Histopathology of the patient's tissue sample showed proliferation of abnormal lymphatic and blood vascular endothelial cells, osteoclasts, and activated macrophages. The activating KRAS variant is a known 'hotspot' variant, frequently identified in several types of human cancer. This is the first report of identifying a pathogenic variant in a patient with GSD. This finding may set the stage for elucidation of pathophysiology and the development of novel therapies for GSD.

Serum Exosomal Gamma-Glutamyltransferase Activity Increased in Patients with Renal Cell Carcinoma with Advanced Clinicopathological Features.

BACKGROUND: There has been no clinically useful diagnostic or prognostic biomarker for renal cell carcinoma (RCC). Serum γ-glutamyltransferase (GGT) activity has been reported to be a prognostic marker for several types of cancer including RCC. Exosomes or small extracellular vesicles present in body fluids have potential as a biomarker. We have recently demonstrated that GGT activity on exosomes isolated from serum is useful for the differential diagnosis of prostate cancer and benign prostate hyperplasia. In this study, we aimed to examine if serum exosomal GGT activity could be a marker for RCC. METHODS: We examined GGT1 expression and GGT activity in cell lysates and exosomes from culture medium of HK-2 proximal tubule epithelial and RCC cell lines. GGT activity was measured using a fluorescent probe for GGT, γ-glutamyl hydroxymethyl rhodamine green. Serum and serum exosomal GGT activities were measured in patients with RCC. GGT1 expression in RCC tissues was evaluated by immunohistochemical staining. RESULTS: GGT1 levels in exosomes from KMRC-1, OS-RC-2 and 786-O cells were elevated compared with those from HK-2 cells. In exosomes, GGT1 expression correlated with GGT activity determined using a fluorescent probe for GGT. In RCC patients, serum exosomal GGT activity was elevated in those with advanced stages (III/IV vs. I/II, p = 0.037) and those with microvascular invasion (with vs. without, p = 0.034). Immunohistochemical analysis showed that membranous GGT1 expression was increased in RCC with microvascular invasion. Notably, preoperative serum exosomal GGT activity could predict the likelihood of having microvascular invasion diagnosed by pathological examination of surgically resected specimens. CONCLUSIONS: Our results suggest that serum exosomal GGT activity could be a clinically useful marker for advanced clinicopathological features of RCC patients, and its combined use with conventional diagnostic modalities may improve the diagnosis and treatment of patients.

Endoscopic and Pathological Characteristics of Helicobacter pylori Infection-Negative Early Gastric Cancer.

BACKGROUND: The characteristics of Helicobacter pylori (HP) infection-negative gastric cancer (HPINGC) have not been well documented because of the rareness. The aim of this study was to classify HPINGC endoscopically and clinicopathologically. METHODS: This retrospective study included 1,741 early gastric cancer lesions and evaluated their HP infection status. Expression levels of MUC5AC, MUC6, MUC2, CD10, p53, MIB-1, pepsinogen-I, H+/K+ ATPase, chromogranin A, E-cadherin, and gastrin were evaluated in tumors by immunohistochemistry (IHC). RESULTS: Among the analyzed lesions, 19 (1.1%) were diagnosed as HPINGC and classified into 6 types: undifferentiated (5 lesions), fundic gland (2 lesions), cardiac gland (1 lesion), pyloric gland (3 lesions), foveolar (5 lesions), and mixed (3 lesions) types. Undifferentiated lesions were of pale color, with unclear demarcation and decreased E-cadherin expression. Fundic-type lesions were tan to reddish in color, with submucosal tumor-like protrusions, and positive for pepsinogen-I and H+/K+ ATPase. The cardiac gland type was located in the gastroesophageal junction and was positive for MUC6 and pepsinogen-I. Pyloric gland-type lesions were of the same color as normal mucosa, with mild elevation and unclear demarcation, likely positive for CD10 and chromogranin A. Foveolar epithelial-type lesions were white and elevated, with defined demarcation, and contained MUC5AC-positive cells. Mixed-type lesions, showing various staining patterns in IHC, had both elevated and depressed shape and reddish color. CONCLUSION: Endoscopic observation and IHC were useful for classifying the characteristics of HPINGC, which may preserve the characteristics of its region of origin.

[Retroperitoneal Dedifferentiated Liposarcoma which Could Be Diagnosed Using Dual Color in Situ Hybridization : A Case Report].

Ten years ago, a seventy-year-old female underwent extirpation of a left retroperitoneal tumor that was 58×36 mm in size. The pathological diagnosis was malignant peripheral nerve sheath tumor (MPNST) at that time. The patients visited our hospital with the chief complaint of back pain at ten years after surgery. Computer tomography (CT) showed recurrent tumors at the pancreas and the left kidney. Fine-needle aspiration biopsy was performed because of the possibility of pancreatic tumor. The pathological diagnosis was the recurrence of MPNST. The patient underwent extirpation of the recurrent tumors along with the pancreatic body and tail, transverse colon, spleen and left kidney. The definitive diagnosis was dedifferentiated liposarcoma with murine double minute 2 (MDM2) gene amplification and positive of p16Ink4 (p16). The previously resected tumor also revealed MDM2 gene amplification and positive of p16. Based on these results, our diagnosis in this case was recurrence of dedifferentiated liposarcoma. At 6 months after surgery, the patient had no local recurrence or distant metastases.

A case of lung adenocarcinoma complicated by pulmonary talcosis occurring in a patient employed in the confectionery industry.

A 73-year-old Japanese man, who worked at a confectionery company for more than 20 years, was diagnosed with a 28 mm nodular lesion in the superior lobe of the right lung by whole-body computed tomography examination. A biopsy revealed the presence of adenocarcinoma. With a diagnosis of a primary lung cancer, a right upper lobectomy was performed. A nodular lesion, 25 × 23 mm in size, was observed in the upper right lobe lung field, and was diagnosed histopathologically as a papillary adenocarcinoma. In addition, fibrous scars in the central part of the tumor showed numerous Langhans and/or foreign body giant cells, and histiocytic cells that had phagocytized numerous small transparent crystals, together with coal powder deposition. The extracted crystals were observed with a scanning electron microscope, and although plate-like structures were observed, ferruginous bodies suggestive of asbestos were not found. The crystals were demonstrated to be talc by powder X-ray diffraction. Herein, we investigated a case of lung adenocarcinoma in a patient with talcosis, with discussions based on a literature search. This collision of talcosis and lung adenocarcinoma adds to an increasing body of knowledge on an apparent association between talc and cancer cases.

p53 Expression as a Diagnostic Biomarker in Ulcerative Colitis-Associated Cancer.

Ulcerative colitis (UC) is defined as an idiopathic inflammatory disorder primarily involving the mucosa and submucosa of the colon. UC-associated colon cancers (also known as colitic cancers) develop through the inflammation-dysplasia sequence, which is a major problem affecting the prognosis of patients with UC. It is therefore very important to detect malignancy from UC at an early stage. As precancerous lesions arising in UC, there are pathological adenomatous changes, basal cell changes, in situ anaplasia, clear cell changes, and pan-cellular change. It is considered that the mutation of the p53 gene plays a crucial role, and the protein expression of p53 in dysplastic crypts may serve as a good biomarker in the early stages of UC-associated colon carcinogenesis. Immunohistochemistry for p53 is a very valuable diagnostic tool in UC-associated colon cancers. However, protein expression of p53 is not always universal, and additional methods may be required to assess p53 status in UC-associated colon cancers.

[A case of an elderly patient with inverted Meckel's diverticulum with small intestinal bleeding detected using capsule and double-balloon endoscopies].

An 80-year-old man was examined with esophagogastroduodenoscopy and colonoscopy because of digestive tract hemorrhage;however, no specific cause was found. Small intestinal capsule endoscopy revealed a reddish elevated lesion in the ileum. This lesion was also detected using double-balloon endoscopy as a 5-cm reddish elevated lesion covered with normal villous architecture in the 95-cm part of the Bauhin valve on the oral side. The lesion was laparoscopically resected and diagnosed as inverted Meckel's diverticulum based on pathological examination. This was a rare case where Meckel's diverticulum was inverted, and the lesion was observed using capsule and double-balloon endoscopies before surgery. Although complications of Meckel's diverticulum are rare in the elderly, it is necessary to identify this disease as a cause of small intestinal bleeding, even in elderly patients.

18-F fluorodeoxyglucose uptake in positron emission tomography as a pathological grade predictor for renal clear cell carcinomas.

OBJECTIVES: To evaluate the usefulness of Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18-F FDG-PET/CT) in the prediction of Fuhrman pathological grades of renal clear cell carcinoma (cRCC). METHODS: This retrospective study was approved by our institutional review board, and written informed consent was waived. Thirty-one patients with pathologically proven cRCC underwent 18-F FDG-PET/CT for tumour staging. Maximum standardized uptake value of cRCC (tumour SUVmax) and mean SUV of the liver and spleen (liver and spleen SUVmean) were measured by two independent observers. Tumour SUVmax, tumour-to-liver SUV ratio, and tumour-to-spleen SUV ratio were correlated with the pathological grades. RESULTS: Logistic analysis demonstrated that only the tumour-to-liver SUV ratio was a significant parameter for differentiating high-grade (Fuhrman grades 3 and 4) tumours from low-grade (Fuhrman grades 1 and 2) tumours (P = 0.007 and 0.010 for observers 1 and 2, respectively). Sensitivity, specificity, and positive and negative predictive values for detecting tumours of Fuhrman grades 3 and 4 were 64, 100, 100, and 77%, respectively, for observer 1, and 79, 88, 85, and 83%, respectively, for observer 2. CONCLUSIONS: The tumour-to-liver SUV ratio with 18-F FDG-PET/CT appeared to be a valuable imaging biomarker in the prediction of high-grade cRCC. KEY POINTS: • Tumour SUV max was correlated with the Fuhrman grades. • High-grade tumours have significantly higher SUV max than low-grade tumours. • Tumour-to-liver SUV ratio is useful in the prediction of high-grade cRCC.

[Small cell carcinoma of the prostate effectively treated for relatively long term: a case report].

A 72-year-old Japanese man was referred to a hospital because of urinary retention. Digital rectal examination revealed a stony, hard nodule in the prostate. A high level of serum PSA was not detected. Prostatic biopsy was performed, and pathological examination indicated adenocarcinoma of the prostate. He was referred to our hospital for treatment. Imaging examinations revealed no metastases (T4N0M0), so we re-evaluated the biopsy specimens. Immunohistochemical examination revealed prostatic small cell carcinoma. His levels of neuron-specific enolase (NSE) and pro-gastrin-releasing peptide (Pro-GRP) were high. We treated him with combination chemotherapy comprising irinotecan and cisplatin, and the treatment was effective. After four courses of the chemotherapy, levels of NSE and Pro-GRP had decreased, and the prostatic mass had decreased in size. Needle rebiopsy of the prostate demonstrated no evidence of malignancy. Adjuvant external beam radiation therapy was also performed. The patient iss till alive at 18 month after diagnosis with no evidence of relapse or metastasis of the disease.

Lumbar clear cell meningioma mimicking schwannoma 7 years after resection of the same type of intracranial tumor: a case report.

BACKGROUND: Meningioma is the second most common intradural extramedullary tumor, following schwannoma. Meningioma is primarily categorized as benign World Health Organization grade 1, but clear cell meningioma is grade 2 of the intermediate malignant category. Clear cell meningiomas are rare, accounting for less than 1% of all meningioma tumors. There is no previous report of multiple intraspinal clear cell meningiomas without dural attachment. CASE PRESENTATION: A 27-year-old Asian male patient presented with lower right extremity pain, and had undergone tumor resection for intracranial clear cell meningioma 7 years previously, with re-resection and radiotherapy for local tumor recurrence at our hospital's department of neurosurgery being carried out 4 years previously. No recurrence was observed since then. Preoperative lumbar magnetic resonance imaging showed two tumors at the L1 and L4 levels, both mimicking schwannoma with well-defined margins, no dural tail sign and homogeneous internal contrast. Intraoperative findings on tumor resection showed two tumors contiguous with the right L2 and L5 roots, which were not attached to the dura mater, similar to a schwannoma. After gross total resection, the postoperative pathology revealed no nuclear SMARCE1 antibody staining. The patient was diagnosed with clear cell meningioma. The patient's postoperative course went well, with no symptoms of nerve dropout and no recurrence 2 years after surgery. In this case, both lumbar lesions were well demarcated and spherical in shape, occurring with single roots. Tumor characteristics suggested a primary rather than a metastatic lesion. Clear cell meningioma is characterized by a SMARCE1 mutation and is different from other types of meningiomas. CONCLUSION: To the best of our knowledge, this is the first report of multiple intraspinal clear cell meningiomas without dural attachment at the lumbar spine after resection of intracranial clear cell meningioma. We speculate that the two tumors were de novo lesions on the basis of the features of the tumors, although they were detected 7 years after the resection of intracranial clear cell meningioma.

Rapid expansion of a left atrial myxoma caused by acute multiple internal hemorrhages: a case report and literature review.

BACKGROUND: Left atrial myxoma is the most common benign tumor, with the growth rate remaining unknown because specific symptoms do not present until the tumor grows to a certain size. Early surgical management is performed in most cases once it is detected by physicians. Despite cardiac myxomas commonly being perceived as slow-growing tumors, rapid enlargement of myxomas has been reported. CASE PRESENTATION: A 64-year-old woman was referred to our hospital with a diagnosis of a left atrial tumor. The pointed tumor changed morphologically in a few hours, and her respiratory condition, which had been normal at admission, suddenly deteriorated. Emergent surgery was performed, and the diagnosis was myxoma with multiple intratumor massive hematomas. The patient recovered uneventfully and was discharged on postoperative day 12 without any complications. CONCLUSIONS: We report an extremely rare case of left atrial myxoma rapidly expanded due to acute multiple hemorrhages within itself. Massive internal hemorrhage alters the size, shape, and fragility of the tumor. We should recognize the potential risk of internal hemorrhage that may lead to acute deterioration of the so-called "slow-growing benign" tumors, such as myxomas.

A Case of Unresectable Combined Hepatocellular-cholangiocarcinoma Treated with Combination Therapy Consisting of Durvalumab Plus Tremelimumab.

Combined hepatocellular cholangiocarcinoma is a rare and challenging primary liver malignancy that lacks any established standard treatments for unresectable cases. We herein present the first known case of a 49-year-old woman diagnosed with unresectable combined hepatocellular-cholangiocarcinoma, who underwent novel chemotherapy involving durvalumab plus tremelimumab combination therapy. The treatment was temporarily discontinued owing to immune-related adverse events, such as rash, and the patient was subsequently managed with systemic steroid therapy; however, the disease progressed after two courses of this treatment. Further studies are needed to validate the efficacy and safety of immune checkpoint inhibitors such as durvalumab and tremelimumab for the treatment of unresectable combined hepatocellular cholangiocarcinoma.

Discrepancy in the Location of Prostate Cancer Indicated on Biparametric Magnetic Resonance Imaging and Pathologically Diagnosed Using Surgical Specimens.

Accurate diagnosis of the localization of prostate cancer (PCa) on magnetic resonance imaging (MRI) remains a challenge. We aimed to assess discrepancy between the location of PCa pathologically diagnosed using surgical specimens and lesions indicated as possible PCa by the Prostate Imaging Reporting and Data System on MRI. The primary endpoint was the concordance rate between the site of probable clinically significant PCa (csPCa) identified using biparametric MRI (bpMRI) and location of PCa in the surgical specimen obtained using robot-assisted total prostatectomy. Among 85 lesions identified in 30 patients; 42 (49.4%) were identified as possible PCa on MRI. The 85 PCa lesions were divided into positive and negative groups based on the bpMRI results. None of the patients had missed csPCa. Although the diagnostic accuracy of bpMRI was relatively high for PCas located in the middle of the prostate (p = 0.029), it was relatively low for PCa located at the base of the prostate, all of which were csPCas. Although current modalities can accurately diagnose PCa, the possibility that PCa is present with multiple lesions in the prostate should be considered, even if MRI does not detect PCa.

Two cases of flow void sign of temporal bone metastasis from follicular thyroid carcinoma.

This report describes CT and MRI findings of temporal bone metastasis from follicular thyroid carcinoma in two cases. Both of these had large, osteolytic, hypervascular masses of the temporal bone, accompanied by internal scattered bone fragments and extraosseous mass formation on unenhanced and contrast-enhanced CT images. In the first case, several dilated and tortuous vessels within the markedly hypervascular mass were observed on the arterial phase of dynamic contrast-enhanced CT images. Compared with the signal intensity of the cerebellum, temporal bone masses showed slightly hypo- to slightly hyperintense on T1-weighted images and slightly hypo- to moderately hyperintense on T2-weighted images. Both cases had flow voids in abnormally dilated vessels within the mass on T1- and T2-weighted images. Thyroid follicular carcinoma rarely metastasizes the temporal bone and presents with an osteolytic hypervascular mass with flow void sign.

Clinical Predictors of Grade Group Upgrading for Radical Prostatectomy Specimens Compared to Those of Preoperative Needle Biopsy Specimens.

BACKGROUND: Decision-making and selection of treatment modalities for newly diagnosed prostate cancer (PCa) are often determined by risk stratification using grade group (GG), prostate-specific antigen (PSA), and clinical stage. The discrepancies between needle biopsy (NB) and radical prostatectomy (RP) specimens often occur because of the sampling errors in NB or multifocal features of PCa. Thus, we aimed to estimate the preoperative clinical factors for predicting GG upgrading after robot-assisted RP (RARP). METHODS: In this retrospective study, we reviewed the clinical and pathological records of patients who underwent RARP at Gifu University Hospital. We focused on patients with organ-confined PCa who had not received neoadjuvant therapy prior to RARP. The primary endpoint was identified as the predictive factor of GG upgrading for RARP specimens compared to those of NB specimens. RESULTS: Eighty-one patients were included in this study. The enrolled patients were divided into two groups: those who had GG upgrading for RARP specimens (the NB upgrade group) or those who did not have GG upgrading (the no upgrade group). The median age of all patients was 70 years, and the median body mass index (BMI) was 22.9 kg/m2. The median neutrophil count was 3720/µL, lymphocyte count was 1543/µL, and neutrophil-to-lymphocyte ratio (NLR) was 2.24. In univariate analysis, BMI, PSA, neutrophil count, and NLR were significantly associated with GG upgrading in RARP specimens compared to NB specimens. BMI and NLR were identified as strong predictive factors for GG upgrading in RARP specimens in the multivariate analysis. CONCLUSIONS: Although this study's small number of enrolled patients was a vital weakness, BMI and NLR might have been significantly correlated with GG upgrading for RP specimens compared with NB specimens. Therefore, BMI and NLR may have potential benefits for newly diagnosed patients with PCa in terms of decision-making and the selection of treatment modalities.

Atraumatic splenic rupture and infection-related glomerulonephritis in a patient with infected aortic aneurysm: A case report.

INTRODUCTION: Atraumatic splenic rupture is very rare and the case is often difficult to determine. We report a case of atraumatic splenic rupture in a patient with an infected aortic aneurysm. CASE PRESENTATION: A 40-year-old man under evaluation and treatment for renal dysfunction presented with the sudden onset of epigastric pain. The patient had a previous history of aortic arch replacement for Stanford type B aortic dissection. Contrast-enhanced computed tomography revealed intraabdominal hemorrhaging around the spleen and intrasplenic extravasation of contrast medium, and atraumatic splenic rupture was diagnosed. The patient slipped into hemorrhagic shock, and emergency splenectomy was scheduled. The histopathological diagnosis was splenic rupture with splenic infarction. The patient became febrile on postoperative day 10. Repeat contrast-enhanced computed tomography revealed enlargement of a cystic aortic aneurysm that was present prior to splenectomy. Infected aortic aneurysm was suspected, which was confirmed following thoracic endovascular aortic repair performed on postoperative day 12. DISCUSSION: We consider that splenic rupture occurred following infected of the kidney and spleen by an infected aortic aneurysm. CONCLUSION: Infection should be considered as a cause in patients with atraumatic splenic rupture.

[Longitudinally Extensive Transverse Myelitis Caused by Granulomatous Primary Central Nervous System Vasculitis with Characteristic Brain Magnetic Resonance Image: A Case Report].

We report a case of primary central nervous system vasculitis (PCNSV) with longitudinally extensive transverse myelitis. A 47-year-old woman presented with malaise, progressive cognitive impairment, and lower limb spasticity. Diffuse hyperintense areas in the deep cerebral white matter on the diffusion-weighted image and T2-weighted images were observed during brain magnetic resonance imaging. Gadolinium-enhanced T1-weighted images showed multiple linear enhancements. A sagittal T2-weighted image displayed a longitudinal extensive lesion of transverse myelitis in the spinal column from the upper cervical (C7) to the thoracic region (Th12). On brain biopsy, the patient was diagnosed as having granulomatous primary angiitis of the central nervous system (PCNSV). This case suggests that PCNSV could show longitudinally extensive transverse myelitis. (Received 14 January, 2021; Accepted 18 February, 2021; Published 1 August, 2021).

A case of multiple metastatic sarcomatoid renal cell carcinoma with complete response to nivolumab.

BACKGROUND: Sarcomatoid renal cell carcinoma (SRCC) is associated with poor prognosis. Although there is no standard treatment for SRCC, recent studies have reported the effectiveness of immune checkpoint inhibitors. CASE: An 82-year-old Japanese man presented to our hospital with an incidental right renal tumor. Abdominal computed tomography (CT) showed an exophytic tumor in the right kidney with suspected right iliopsoas muscle invasion. Laparoscopic right radical nephrectomy was performed. Histopathological diagnosis revealed a clear cell RCC with a spindle cell carcinoma component. CT performed 3 months after surgery revealed multiple bilateral lung metastases and local recurrence. Although the patient received tyrosine-kinase inhibitors for treating multiple metastases, the lung metastases continued to gradually increase, and peritonitis carcinomatosis was observed. Thus, the patient was intravenously administered nivolumab once every 2 weeks. After nivolumab administration, lung metastases, local recurrence, and peritonitis carcinomatosis gradually reduced. After 20 months of nivolumab treatment, the patient achieved a complete response of multiple metastases on CT. CONCLUSION: Nivolumab may be used as a treatment option for sarcomatoid renal cell carcinoma with multiple metastases.