Alveolar soft part sarcoma(ASPS)is a rare malignant tumor whose origin is unidentified, arising from deep soft tissue and affecting adolescents and young adults. ASPS is characterized by its abundant vascular network forming alveolar structures, and demonstrates frequent hematogenous metastasis. An ASPSCR1-TFE3 fusion gene derived from t(X;17)chromosome translocation is detected as a disease gene in all cases, and the ASPSCR1-TFE3 protein causes abnormal transcriptional regulation. We generated a mouse model for ASPS by introducing ASPSCR1-TFE3 into mouse embryonic mesenchymal cells. In the model, tumor angiogenesis and alveolar structures of human ASPS were reproduced, revealing pericyte-rich blood vessels and metastatic processes with pericytic encapsulation of tumor cell nests. ASPSCR1-TFE3 is frequently associated with active enhancers and super-enhancers, and angiogenesis-related enhancers were significantly diminished by the loss of ASPSCR1- TFE3. Angiogenesis-associated enhancers and important target genes, Rab27a, Sytl2, Pdgfb and Vwf were identified by epigenetic CRISPR screening. Rab27a and Sytl2 facilitates trafficking of cytoplasmic vesicles containing angiogenic factors such as Pdgfb and Vwf, resulting in pericyte-rich vascular structures in ASPS. These studies highlight the importance of the Rab27/Sytl axis as a novel drug target in cancer.

Cancer precision medicine (genome-based individualized treatment for cancer patients) has already been introduced for solid tumors, and involves identifying driver genes in the development and progression of tumors and suggesting optimal treatments targeting those genes. So far, many patients have received this style of treatment. Meanwhile, preparations for cancer genomic medicine based on cancer gene panel testing are also underway for hematopoietic tumors. In this article, I would like to share fundamental information about the main genetic mutations in malignant lymphomas and their clinical significance, and discuss how this information should be utilized in cancer genomic medicine in the future.

A 21-year-old man who was diagnosed with Ollier disease at the age of 1 year developed incidental multiple gliomas at the age of 15 years. Subsequently, the multiple gliomas enlarged and the patient underwent three surgical removals. Genetic analysis revealed the IDH1 p.R132C mutation in the gliomas, and histopathology showed malignant transformation. Despite multimodality treatment, the gliomas could not be controlled, and the patient died at the age of 23 years. Ollier disease is a rare disease with IDH1/2 mutations and is often associated with gliomas. However, there are very few reports on genetic analysis of IDH1/2 mutations and long-term follow-up in Ollier disease-related gliomas. Genetic analysis of IDH mutations may contribute to the elucidation of its pathogenesis. The cross-departmental collaboration is required for long-term follow-up of Ollier disease-related gliomas.

An 80-year-old woman had developed a slight fever and loss of appetite since October 20XX. In November of the same year, the patient visited our hospital. Peripheral blood tests revealed the presence of atypical lymphocytes and a significant increase in sIL-2R. Tests of bone marrow aspiration samples showed the infiltration of small lymphocytes positive for CD19, CD20, CD23, and lambda. Therefore, a diagnosis of small lymphocytic lymphoma(SLL)was made. A complex karyotype including -X and del(13q)was observed in 19/20. Additionally, an enlarged spleen and retroperitoneal tumors were observed. As a result of 3 courses of fludarabine plus rituximab therapy, atypical lymphocytes were no longer observed in the peripheral blood and the enlarged spleen decreased in size. However, the retroperitoneal tumors could not be reduced. Consequently, a needle biopsy from the same area was performed in February 20XX+1, and a diagnosis of diffuse large B-cell lymphoma(DLBCL)was made. Because massive infiltration of CD23-negative lymphocytes was observed in the bone marrow, it was suggested that chronic lymphocytic leukemia(CLL)had transformed into DLBCL. Following 4 courses of CHOP therapy, the retroperitoneal tumors were reduced. In cases where -X is a microclone, the mutation is often age-related. However, in cases of advanced chronogenesis, as occurred in this patient, a correlation with hematopoietic tumors is arguable. Moreover, cases of CLL with -X have been reported to be related to de(l 13q). Our results strongly suggest that -X with del(13q)may be a clonal expansion in CLL/SLL.

A Japanese woman in her early 70's presented to our hospital with abdominal pain and nausea. Abdominal computed tomography showed irregular wall thickening of the ileocecal region and small intestine dilatation. Colonoscopy revealed a tumor lesion at the ileocecal valve and adenocarcinoma was detected in the biopsy specimen. Accordingly, the diagnosis was cecal cancer and bowel obstruction. Right hemicolectomy was performed as palliative surgery, and laparotomy findings revealed peritoneal dissemination. The final staging was pT4a, pN2b, pM1c, pStage Ⅳc, harboring a BRAFV600E mutation. Rapid postoperative tumor progression occurred, leading to multiple liver metastases and ascites. Encorafenib, binimetinib, and cetuximab triple therapy was started as a second line regimen. The therapy was extremely effective. CA19-9 level decreased to within normal range, and the liver tumor size was visibly diminished. After receiving treatment for 2 months in outpatient care, she had to discontinue the treatment due to carcinomatous peritonitis. Unfortunately, she died 6 months after initial diagnosis. BRAF-mutated colon cancer is associated with poor prognosis. In Japan, encorafenib, binimetinib, and cetuximab triple therapy is a new BRAF targeting regimen approved in 2020. We report this clinical course in hopes of eventually achieving better outcomes for patients with this aggressive disease.

The blood cancer field has played a pioneering role in advancing precision medicine, with milestones such as development of ABL1 inhibitors for chronic myeloid leukemia. The significance of gene mutation information in AML treatment has increased, evident in classifications and guidelines from organizations such as WHO and ELN. This article examines the anticipated roles of cancer genome panels (CGPs) in AML treatment from three perspectives: diagnosis, risk stratification, and treatment selection. Use of CGPs enables more accurate diagnosis and risk stratification. In treatment selection, CGPs not only complements but also substitutes existing companion diagnostics, and is expected to be a crucial information source for future drug adoption and investigation of tumor-agnostic therapies. However, various challenges remain to be addressed, including the purpose and timing of CGPs, the time required for the tests, and how to utilize expert panels.

As of December 2023, there are 5 types of cancer gene panel tests covered by public insurance in Japan. Four of them partly feature companion diagnostics. When cancer gene panel test is used for the purpose of comprehensive gene profiling (CGP), a total of 56,000 points(44,000 points for the test administration fee and 12,000 points for the expert panel fee) can be claimed, whereas if the cancer gene panel test is used for the purpose of companion diagnostics, hospitals can claim only the reimbursement as a companion diagnostics, which fee is much cheaper than that of CGP. Therefore, cancer gene panel tests are rarely used as a companion diagnosis in daily clinical practice. Even when the test is performed as a CGP test, since its indication is limited to patients who have completed or are expected to complete standard chemotherapy, most biomarkers associated with approved drugs are already evaluated with stand-alone companion diagnostics at the time of CGP test application. On the other hand, there are some approved drugs, such as pembrolizumab for TMB-H or entrectinib or larotrectinib for NTRK fusion gene, for which there is no stand-alone companion diagnostics and the eligibility for these drugs cannot be judged without the results of CGP test. This paper discusses the current status and issues of companion diagnostics in cancer genomic medicine.

As genomic medicine advances, opportunities for molecular pathology diagnosis by pathologists to be used as companion diagnostics is increasing. Pathological specimens must be useful not only for pathological diagnosis, but also for genetic testing panel and molecular pathology diagnosis. Companion diagnostics performed by pathologists uses immunohistochemical staining and fluorescence in situ hybridization to determine patient eligibility for molecular target drugs and immune checkpoint inhibitors. By accurately observing a wide variety of diagnostic criteria and performing with high precision, pathological diagnosis will become closer to therapeutic pathology.

There have been many driver gene abnormalities identified in NSCLC, and the development and clinical adoption of targeting drugs for such are progressing. This has, as a result, complicated the situation surrounding companion diagnostics (CDx). Lung cancer treatment guidelines recommend the use of Multiplex testing that allow for CDx for many driver gene abnormalities to be used prior to 1L treatment for advanced lung cancer. The problem is that insurance rules stipulate that only one of Multiplex test is deemed reimbursable per junction in time, particular CDx are linked to particular targeted drugs instead of particular driver gene abnormalities, and none of the currently available Multiplex tests contain the CDx for all genetic mutations for which drugs have been approved. This results in a fair number of cases in which regulatory issues ensue. It is also very difficult to obtain enough of a tissue sample to get accurate results in Multiplex testing for advanced NSCLC. CDx are not full-proof, as results must be interpreted with a consideration of the potential for a false-negative due to the nature of tests. This paper, therefore, will focus on the issues with CDx from the viewpoint of medical oncologists in the clinical setting.

Companion diagnostics(CDx)are in vitro diagnostic products that are used to predict the efficacy and adverse effects of therapeutic drugs prior to administration, and are co-developed and co-approved with the therapeutic drugs in principle. In Japan, 40 CDx products have been approved by January 2024, and 39 products are used to determine if therapeutic drugs are applicable for cancer treatment. In the CDx products for cancer treatment, PCR, immunohistochemistry, or in situ hybridization is used to clarify the mutations(point mutations, insertions/deletions, fusions, etc.)in cancer-related genes or the expression levels of cancer-related molecules in the cancer tissues. The results of the analysis determine whether a particular therapeutic drug could be used or not for the treatment of the corresponding patient. Recently, several next-generation sequencing(NGS)-based CDx products have been approved and utilized for cancer treatment. The rise of NGS-based diagnostics has made it possible to comprehensively analyze mutations in many cancer-related genes in a single test and to determine whether each of several therapeutic drugs is applicable to the patient at once. On the other hand, with the increase in the number of CDx products, several regulatory issues have arisen, including an issue related to the co-development of CDx and a therapeutic drug and an issue related to the interchangeable use of CDx products that detect the same mutations of the cancer-related genes. The revision of CDx-related guidance is being considered in Japan and overseas in response to this situation.

A 2-year-old, male patient presented with an 18-month history of scattered, brown macules and nodules up to 2 cm in size on his trunk and extremities. These macules were accompanied by pruritus and were positive for Darier's sign. A skin biopsy of a brown macule on the left thigh revealed a dense accumulation of CD117-positive, round or oval cells with amphophilic cytoplasm within the upper to middle dermis. The patient was otherwise healthy and had normal laboratory and imaging test results. Sequence analysis of genomic DNA from a skin biopsy demonstrated the presence of an Asp419del mutation in exon 8 of the KIT gene. Based on these findings, maculopapular cutaneous mastocytosis (MPCM) was diagnosed. The patient received H 1-antihistamine. Although the pruritus resolved, the brown macules remained for one year after the initial treatment. To the best of our knowledge, only three cases of cutaneous mastocytosis (CM) with an Asp419del mutation, including the present case, have been reported in the Japanese literature to date; moreover, while the previous two cases were of DCM, the present case was the first instance of MPCM. Normally, the symptoms of childhood-onset MPCM are dormant until puberty. However, a recent study reported that many MPCM patients may experience persistent or exacerbated symptoms. The present study therefore evaluated 53 Japanese cases of childhood onset MPCM with a KIT gene mutation and discussed the patients' clinical outcomes.

A 28-year-old female with a history of treatment for small intestinal polyps and characteristic pigmentation of her lip was clinically diagnosed with Peutz-Jeghers syndrome(PJS). Her sister had the pathogenic variant of STK11 upon genetic testing. A 20-mm polyp was identified in the second part the patient's duodenum on routine gastrointestinal surveillance, and biopsy revealed a well-differentiated adenocarcinoma. Laparoscopic partial duodenectomy with endoscopy was planned. After confirming the location of the tumor and Kocherization using a laparoscope, the polyp was resected via submucosal dissection under direct visualization with a small incision. The polyp was diagnosed as well-differentiated adenocarcinoma in situ and was resected without remnants. PJS is characterized by a high incidence of malignant tumors, and lifelong surveillance for gastrointestinal and extra-gastrointestinal tumors is necessary. The incidence of duodenal cancer is not high among patients with PJS. However, surgery for advanced cancer is highly invasive. It is desirable to detect the tumors at an early stage so that they can be resected via a less invasive treatment method such as endoscopic resection or laparoscopic surgery with an endoscope.

Cytotoxic chemotherapeutic agents are defined by the AACR as traditional chemotherapy and have long been a mainstay of cancer treatment. Many of these drugs have been developed through screening natural substances. The efficacy of these drugs for non-small cell lung cancer was demonstrated by a 1995 meta-analysis, which showed an extension of survival time with cisplatin. Although numerous drugs have been developed, combinations such as carboplatin with paclitaxel and cisplatin with gemcitabine have been standard treatments. The development of molecularly targeted therapy represents a significant advance in the treatment of lung cancer, with EGFR inhibitors first approved in Japan. Predictive factors for therapeutic effect have been identified as specific abnormalities in the EGFR gene, and it has been shown that resistance due to secondary mutations in the gatekeeper region occurs, and that increasing specificity for genetic abnormalities enhances drug efficacy. Subsequently, genetic abnormalities causing multiple cancers have been identified, and corresponding drugs have been developed. Immunotherapy has shown the effectiveness of immune checkpoint inhibitors. In lung cancer, the therapeutic effect of PD-1/PD-L1 inhibitors was demonstrated early on. Currently, immunotherapy is standard treatment from the first-line for patients likely to respond well to it, and in combination with chemotherapy for others. Furthermore, as an adjunct to curative treatment, combinations of molecularly targeted therapy and immune checkpoint inhibitors have shown to extend survival. This indicates that a composite approach is beneficial for patient prognosis.