We report a rare case of a solitary metastasis in which long-term complete remission was achieved with chemotherapy alone. An 81-year-old woman underwent a right hemicolectomy and D3 lymph node dissection for ascending colon cancer. Pathological findings showed type 2, 40×20 mm, tub2>muc, pT3, int, INF b, ly1, v0, pN1(1/32), pPM0, pDM0, and fStage Ⅲa. However, the patient chose not to undergo adjuvant chemotherapy and opted for further observation. Five months after the surgery, lymph node metastasis was observed near the right external iliac artery. Because the patient did not wish to undergo surgical treatment, SOX therapy was initiated. Owing to considerable side effects, the patient's treatment was switched to oral S-1. Gradually, the lesion disappeared, and the treatment was changed to UFT. The patient has maintained complete long-term remission for 10 years postoperatively. Here, we report this case along with a literature review.

While recent advances in chemotherapy for pancreatic cancer have improved treatment outcomes, pathological complete responses(pCR)remain rare. Here, we present four cases of pancreatic cancer in which a pCR was achieved following chemotherapy. Three cases were classified as borderline resectable and one was resectable. Two patients received gemcitabine+nab-paclitaxel, 1 received mFOLFIRINOX, and one received gemcitabine+S-1 therapy. Histopathological examination after resection revealed only fibrosis and scarring. No tumor cells were found in any of these cases, leading to diagnoses of pCR. Two of the 4 patients survived without recurrence for a long time. The other 2 patients experienced recurrence, one of whom died 8 months after surgery.

The patient was a 79-year-old male diagnosed with gastric cancer with lung metastasis(cT3N2M1[PUL], cStage ⅣB)and sigmoid colon cancer(cT3N0M0, cStage Ⅱa). He underwent systemic chemotherapy with the SOX plus nivolumab regimen for unresectable advanced gastric cancer. Six months after the initiation of chemotherapy(9 courses), the primary tumor and lymph node metastases in the lesser curvature and suprapancreatic margin had shrunk, and the lung metastases had disappeared. However, chemotherapy was discontinued because of the development of immune-related interstitial pneumonia, and steroid therapy was initiated. Nine months after the initiation of chemotherapy, the tumor shrinkage rate remained constant and interstitial pneumonia improved; however, the patient was referred to our hospital for surgical treatment for gastric stenosis. A laparoscopic distal gastrectomy was performed for gastric cancer. Histopathological findings revealed no residual cancer cells in the primary tumor or lymph nodes, and the histological response was Grade 3. The patient remained recurrence-free for 10 months after the surgery. SOX plus nivolumab therapy for unresectable advanced gastric cancer is expected to have a high tumor-shrinkage effect, and combining it with conversion surgery may lead to an improved long-term prognosis.

A woman in her 60s visited our hospital after colonoscopy revealed a circumferential type 2 lesion located 10 cm from the anal verge. Computed tomography revealed metastases in liver S4 and S8. The regional lymph nodes were markedly enlarged, compressing the sciatic nerve. The patient was diagnosed with unresectable advanced rectal cancer (cT4aN2bM1a, cStage Ⅳa), and treated with 5 courses of FOLFOXIRI+bevacizumab. The patient subsequently underwent open left lobectomy and cholecystectomy. One month later, a robotic high anterior resection of the primary tumor was performed. Although the patient had undergone laparotomy, robotic surgery was used to ensure complete R0 resection. Liver-first approaches may offer greater benefit for certain patient populations than other treatment strategies, including prior or concurrent resection of the primary lesion. Robotic surgery may also be a viable option for primary colorectal cancer even after open surgery.

A 45-year-old female with a medical history of systemic lupus erythematosus presented with breast cancer. On postoperative day 26 after undergoing left mastectomy and axillary lymph node dissection, she reported fever and anorexia at the outpatient clinic. Laboratory findings showed pancytopenia, and a subsequent bone marrow biopsy confirmed metastatic breast cancer involving the bone marrow. Tamoxifen and goserelin therapy was started initially. However, on the day after treatment initiation, the patient experienced rapid progression of anemia, with laboratory evidence of hemolysis and clinical signs of jaundice and splenomegaly; this led to a diagnosis of autoimmune hemolytic anemia(AIHA). Steroid pulse therapy resulted in a dramatic halt in anemia progression. Given that AIHA is a paraneoplastic syndrome with suspected resistance to endocrine therapy, chemotherapy with paclitaxel was initiated. AIHA recurrence was not observed after this intervention. In cases of breast cancer with bone marrow metastasis and acute anemia, especially in patients with an autoimmune history, a differential diagnosis beyond marrow suppression from metastasis should be carefully considered.

Appendiceal adenocarcinoma(AA), a rare cancer, has been treated as right-sided colon cancer in accordance with colorectal cancer treatment guidelines. However, AA has distinct characteristics compared to colorectal cancer, such as a higher prevalence of mucinous histology and a tendency for peritoneal metastasis. In addition, there are many cases where the histological grade does not correlate with disease progression, and differences in treatment response and prognosis have been reported depending on genetic mutation subtypes. In terms of chemotherapy, in addition to oxaliplatin-based regimens, there have been reports on the efficacy of molecular targeted therapies and immunotherapies. In our multicenter observational study, AA patients with multiple factors such as poor PS, high tumor burden, and moderate to massive ascites had significantly poor prognosis compared to those without. In the future, we need to develop novel therapeutic strategies based on genetic status and tumor biological characteristics.

Appendiceal tumors are relatively rare and their classification remains controversial. In particular, for tumors specific to the appendix, such as appendiceal mucinous neoplasm and goblet cell adenocarcinoma, understanding the disease has become difficult due to transition of terminology and complex grading systems. There has been little large-scale data on appendiceal tumors in Japan, but a full picture is gradually emerging on account of project research by the Japanese Society for Cancer of Colon and Rectum. Now, we explain the overview of appendiceal mucinous neoplasm and goblet cell adenocarcinoma, as well as their histological grading and staging system, including the latest findings, and describe their impact on patient prognosis and treatment. Both of these tumors frequently cause clinical problems due to peritoneal dissemination. In Europe and the United States, the combination of cytoreductive surgery(CRS)and hyperthermic intraperitoneal chemotherapy(HIPEC)is recommended, but in Japan, HIPEC is not widely used, so there is not enough data available. There are still many unknowns about appendiceal tumors, so it is important to clarify the concept of the disease and accumulate accurate data. In addition, the histological classification of appendiceal tumors in this article conforms to Japanese Classification of Colorectal, Appendiceal, and Anal Carcinoma, 9th edition and the WHO Classification, 5th edition, although new editions of both are scheduled to be published soon. The outlook for the 10th edition of the Japanese Classification is briefly mentioned in the text, but please note that the classification introduced here may be subject to change.

A 60-year-old man was diagnosed with a rectal gastrointestinal stromal tumor(GIST). Endoscopy revealed a submucosal tumor in the lower rectum near the dentate line. CT and MRI findings showed that the tumor was compressing the prostate and seminal vesicles. To shrink the tumor whilst preserving the anus, 400 mg/day of imatinib mesylate (IM)was administered as preoperative drug therapy. Six months after the initiation of neoadjuvant therapy, the patient underwent laparoscopic low anterior resection of the rectum. Postoperatively, IM was resumed as adjuvant therapy, but was discontinued after 10 months due to the occurrence of side effects. No recurrence of the tumor was observed during a 2 years and 3 months postoperative assessment. We believe that preoperative pharmacotherapy with IM is an effective treatment strategy. Herein, we report the details of this case along with a review of the literature.

unknown, but she remained symptom-free for 32 years. However, a CT scan performed for an unrelated condition revealed 2 liver tumors with calcifications located in S8(10 cm)and S6(3 cm). Given her medical history, liver metastasis from breast cancer was suspected. Core needle biopsies of the liver tumor and a left axillary lymph node detected on PET-CT, confirmed metastatic breast cancer that was estrogen receptor-positive, progesterone receptor-positive, and human epidermal growth factor receptor 2-negative. Upon diagnosis, chemotherapy with paclitaxel and bevacizumab was initiated. Follow-up CT scans at 6 and 15 months showed continued tumor regression in the liver and axilla. After 15 months of treatment, both tumors continued to shrink. Although late recurrence is common with breast cancer, recurrence more than 30 years post-surgery is rare. This case of late-stage metastatic breast cancer is presented alongside a literature review.

Most castration-sensitive prostate cancers(CSPC)with metastases progress to castration-resistant prostate cancer(CRPC)within a few years. In recent years, upfront treatment with second-generation antiandrogens, novel hormonal agents (ARSIs)and taxanes, administered at the mCSPC stage, has been developed and the evidence of delaying the time to reach CRPC has been reported. However, once the disease progresses to CRPC, there are few treatment options and no effective treatment sequence has been established. Ra223 as radiotherapy for bone metastases in mCRPC treatment has shown prolonged survival benefits, similar to ARSI and taxane-based anticancer drugs, and is widely used in Japan. Recently, prostate-specific membrane antigen(PSMA)-lutetium therapy, in which PSMA is coupled to 177Lutetium and administered systemically, has been developed in Western countries for mCRPC expressing PSMA and is an effective RI therapy that reduces bone and visceral metastases. It is expected to be covered by health insurance in Japan in the near future and is expected to be a promising treatment for mCRPC.

Approximately, 5-10% of differentiated thyroid cancer patients experience distant metastases. 131I radioiodine(RAI)therapy fails in 60-70% of them, resulting that patients of less than 5% are categorized in the RAI refractory group including patients of RAI non-avid lesions and those of RAI avid but insufficient lesions. Redifferentiation of RAI accumulation has been examined with a variety of pharmaceuticals such as MKIs and BRAF/MEK inhibitors. Redifferentiation effects are monitored by scintigraphic findings and RAI therapy can be applied again. The phenomenon that patients with RAI avid lesions would not respond to RAI therapy may be explained by insufficient lesional radiation doses. In such cases, shrinkage of lesions with interventional drugs before RAI therapy would result in increase of lesional radiation doses. Such kind of strategy should be incorporated in future patient management.

Thymic lymphoepithelial carcinoma (LEC) is a rare subtype of thymic cancer and reported in 6% of thymic carcinoma. In terms of histopathology, it closely mimics undifferentiated tumors that originate in the nasopharynx, and in half of the cases, it has been associated to the Epstein-Barr (EB) virus infection. Seven reports have been published on the result of surgical resection, particularly in the early stages of thymic LEC. Recurrence was reported in three patients, and one patient died. In our case, the patient underwent video-assisted thoracoscopic surgery for a partial thymectomy and thymomectomy and was alive without recurrence 92 months after the surgery without adjuvant therapy.

A 65-years-old female was admitted to our hospital for treatment of fever and chest pain. Contrast-enhanced computed tomography (CT) revealed an anterior mediastinal tumor with a thickened wall, and right pleural effusion. Ten days after antibiotic therapy, the fever, chest pain and pleural effusion disappeared. Thymectomy was performed to confirm the diagnosis. Histopathologic diagnosis was type B2 thymoma with extensive necrotic area, Masaoka's stageⅠ. No recurrence has been observed for approximately two years since the surgery. Thymomas have a variety of pathological features such as cystic and hemorrhagic changes and necrosis. However, thymomas with extensive necrosis are very rare. We presented this case with a review of the literature.

Aortic pseudoaneurysm is a rare complication of advanced esophageal cancer. While emergency open aortic surgery is associated with high operative mortality, massive bleeding without treatment is fatal. On the other hand, thoracic endovascular aortic repair (TEVAR) for pseudoaneurysm is far less invasive. We experienced two cases of aortic pseudoaneurysm successfully treated by TEVAR. Case 1:68-year-old male. During preoperative adjuvant chemotherapy for advanced esophageal cancer, he was diagnosed with esophageal non-aortic fistula by computed tomography (CT). Case 2:80-year-old woman. She complained dysphagia, and CT revealed an aortic pseudoaneurysm associated with mediastinal perforation of advanced esophageal cancer and direct invasion to the descending aorta. Considering their general condition, they underwent minimally invasive TEVAR. Clinical condition dramatically improved and they become able to eat well, and they were transferred to the hospice until they died of cachexia due to progression of esophageal cancer.

Cerebellopontine (CP) angle meningiomas are surgically challenging because of their deep-seated location and proximity to the cranial nerves and vessels. Surgical approaches suitable for treating these tumors are described in detail in this article. CP angle meningiomas can be classified into six subtypes based on the tumor attachment location: 1)petrotentrial, 2)anterior petrous, 3)posterior petrous, 4)petroclival, 5)inferior petroclival or jugular tubercle, and 6)pure clival meningioma. The suitable approach for each subtype is described.

A 47-year-old male patient with anal pain underwent a colonoscopy 12 years after Crohn's disease diagnosis. A biopsy from the protuberance of the anal canal revealed a well-differentiated adenocarcinoma. A reexamination of the histopathological specimen at our hospital revealed anal high grade dysplasia (HGD), thereby changing the initial diagnosis. A distal colon resection and rectal amputation were performed, and the final diagnosis of the resected specimen was anal canal HGD. While HGD associated with Crohn's disease is rare in Japan, this case suggests the importance of endoscopic examination, which might help in early detection of HGD.

A woman in her 40s underwent transurethral resection of bladder tumor in September X-2 followed by preoperative chemotherapy for muscle-invasive bladder cancer. She later had robot-assisted radical cystectomy with neobladder cystostomy in February X-1. In July X-1, computed tomography revealed metastasis in the right pulmonary apex and right upper mediastinal lymph node, and a partial resection of these sites was performed. Based on the pathological results, the patient was diagnosed with bladder cancer metastasis. Pembrolizumab was started in December X-1 ; however, right upper mediastinal lymph node enlargement was noted in October X, with progressive growth. In December X, the patient visited her primary care physician due to amnesia and decreased attention. Magnetic resonance imaging (MRI) revealed abnormal signal areas in the right temporal pole and the medial portions of both temporal lobes. Her symptoms worsened after a week, prompting steroid pulse therapy for suspected limbic encephalitis. Although her brain MRI revealed some improvement, her symptoms persisted. Repeated steroid pulse therapy had no effect. Following intravenous immunoglobulin, the patient's symptoms and MRI findings improved. Based on these findings, she was diagnosed with limbic encephalitis due to bladder cancerassociated paraneoplastic neurological syndrome.

A 73-year-old man presented with asymptomatic macroscopic hematuria. Contrast-enhanced computed tomography revealed a mass filling the right renal pelvis, along with a 2cm cystic tumor in the dorsal aspect of the right upper pole. A retroperitoneoscopic nephroureterectomy was performed based on the diagnosis of right renal pelvic carcinoma. Pathological diagnosis confirmed that the right renal pelvic mass was an invasive urothelial carcinoma, classified as G2 with INFa, pT1, ly0, and v0, while the cystic tumor was a chromophobe renal cell carcinoma, classified as G2 with INFb, pT1a, and v0. No postoperative chemotherapy was administered. The patient's recovery was uneventful, and, seven years after the operation, he remains alive with no signs of recurrence or metastasis.

A 64-year-old man was incidentally found to have a right renal tumor during a medical check-up. The tumor was diagnosed as renal cell carcinoma cT1aN0M0 by magnetic resonance imaging and computed tomography, and the left kidney was hypoplastic. Open partial nephrectomy was performed. Postoperatively, lung, stomach, and ipsilateral renal metastases were observed sequentially. By adjusting the dose of IFNα, the progression of cancer was controlled for 18 years while managing the side effects of IFNα. Despite the declining recommendation for IFNα in renal cancer practice guidelines, it may still be a viable treatment option in selected cases.

The development of dual energy CT (DECT) has made it possible to provide not only morphological characteristics but also a wide range of quantitative information. The purpose of this study is to differentiate between benign and malignant solitary pulmonary nodules (SPN) by using electron density values obtained from DECT.