Succinate dehydrogenase-deficient GISTs: a clinicopathologic, immunohistochemical, and molecular genetic study of 66 gastric GISTs with predilection to young age

Gastrointestinal stromal tumors in fine-needle aspiration biopsies

Gastrointestinal stromal tumors (GISTs), although rare, are the most common mesenchymal neoplasms of the gastrointestinal tract. Their potential for malignancy underscores the significance of identifying them through cytomorphologic findings and pertinent immunohistochemical markers. GISTs can emerge anywhere along the gastrointestinal tract with a predilection for the stomach. The clinical manifestations vary from nonspecific abdominal symptoms to incidental discovery during diagnostic interventions for unrelated signs and symptoms. Cytologically, GIST aspirates contain spindle or epithelioid cells with immunoreactivity for CD117/c-KIT, DOG-1, and CD34. Molecularly, KIT or PDGFRA mutations are prevalent, guiding targeted therapy with tyrosine kinase inhibitors. Distinct subtypes like succinate dehydrogenase-deficient GISTs pose challenges, often affecting younger individuals and displaying unique features. Histologically, GISTs are graded by mitotic rates, aiding prognostication. Distinguishing GISTs from similar entities is pivotal, necessitating attention to their immunostaining patterns for making an accurate diagnosis and molecular alterations for effectively planning treatment. Common differential diagnoses include leiomyoma, schwannoma, and solitary fibrous tumor. This article presents a classic GIST case and showcases relatively simple diagnostic clues for identifying similar lesions that may occur in diverse locations.

Gastrointestinal Stromal Tumors (GISTs) in Pediatric Patients: A Case Report and Literature Review

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms that primarily affect adults, with pediatric cases constituting only 0.5-2.7% of the total. Pediatric GISTs present unique clinical, genetic, and pathological features that distinguish them from adult cases. This literature review aims to elucidate these differences, emphasizing diagnostic and therapeutic challenges. We discuss the resistance of pediatric GISTs to conventional chemotherapy and highlight the importance of surgical intervention, especially in emergency situations involving intra-abdominal bleeding. The review also explores the molecular characteristics of pediatric GISTs, including rare mutations such as quadruple-negative wild-type GIST with an FGF3 gene gain mutation. To illustrate these points, we conclude with a case from our clinic involving a 15-year-old female with multiple CD117-positive gastric GISTs and a quadruple-negative wild-type genetic profile who required urgent surgical intervention following a failed tumor embolization. This case underscores the critical need for early diagnosis and individualized therapeutic strategies combining oncologic and surgical care to improve outcomes in pediatric GIST patients.

Molecular Profiling of KIT/PDGFRA-Mutant and Wild-Type Gastrointestinal Stromal Tumors (GISTs) with Clinicopathological Correlation: An 18-Year Experience at a Tertiary Center in Kuwait

In gastrointestinal stromal tumors (GISTs), identifying prototypical mutations in the KIT/PDGFRA oncogenes, or in rare alternate genes, is essential for prognostication and predicting response to tyrosine kinase inhibitors. Conversely, wild-type GISTs (WT-GIST), which lack known mutations, have limited treatment options. Data on the mutational landscape of GISTs and their impact on disease progression are very limited in Kuwait. Using a targeted next-generation sequencing panel, we investigated the spectrum and frequency of KIT, PDGFRA, and RAS-pathway-related mutations in 95 out of 200 GISTs diagnosed at Kuwait Cancer Center from 2005 to 2023 and assessed their correlation with clinicopathological parameters. Among the 200 tumors (median age 55 years; 15-91), 54% originated in the stomach, 33% in the small bowel, 7% in the colorectum, 1.5% in the peritoneum, and 4.5% had an unknown primary site. Of the 95 molecularly profiled cases, 88% had a mutation: KIT (61%), PDGFRA (25%), NF1 (2%), and one NTRK1 rearrangement. Ten WT-GISTs were identified (stomach = 6, small bowel = 2, and colorectum = 2). WT-GISTs tended to be smaller (median 4.0 cm; 0.5-8.0) (p = 0.018), with mitosis ≤5/5 mm2, and were of lower risk (p = 0.019). KIT mutations were an adverse indicator of disease progression (p = 0.049), while wild-type status did not significantly impact progression (p = 0.934). The genetic landscape in this cohort mirrors that of global studies, but regional collaborations are needed to correlate outcomes with genetic variants.

A PDE3A-SLFN12 Molecular Glue Exhibits Significant Antitumor Activity in TKI-Resistant Gastrointestinal Stromal Tumors

PURPOSE

Gastrointestinal stromal tumor (GIST), the most common mesenchymal tumor with KIT or PDGFRA driver mutations, is typically treated with tyrosine kinase inhibitors (TKI). However, resistance to TKIs due to secondary mutations is a common challenge in advanced GISTs. In addition, there are currently no effective therapies for several other molecular subtypes, such as succinate dehydrogenase-deficient GISTs. Therefore, novel therapeutic strategies are needed.

EXPERIMENTAL DESIGN

To address this need, we tested the efficacy of a novel non-TKI compound, OPB-171775, using patient-derived xenograft models of GISTs. In parallel, we sought to elucidate the mechanism of action of the compound.

RESULTS

Our study revealed that OPB-171775 exhibited significant efficacy against GISTs regardless of their KIT mutation status by inducing complex formation between phosphodiesterase 3A (PDE3A) and Schlafen family member 12 (SLFN12), which are highly expressed in GISTs, leading to SLFN12 RNase-mediated cell death. Furthermore, we identified the activation of general control non-derepressible 2 and its downstream response as an effector pathway of SLFN12 in mediating anticancer activity and revealed potential pharmacodynamic markers.

CONCLUSIONS

These findings suggest that OPB-171775, with its significant efficacy, could potentially serve as a novel and effective treatment option for advanced GISTs, particularly those resistant to TKIs.

Recurrence of fusocellular subtype GIST with SDHB mutation: A case of SDHB-loss and therapeutic challenges

Gastrointestinal stromal tumors (GISTs) are sarcomas affecting the stomach and small intestine, with a rare subtype characterized by succinate dehydrogenase B (SDHB)-loss posing significant diagnostic and therapeutic challenges. A 62-year-old man with weight loss and abdominal pain was diagnosed with a gastric GIST showing SDHB-loss. Initial treatment with Imatinib reduced the tumor size, but surgery revealed no residual tumor. Despite adjuvant Imatinib, recurrence occurred, necessitating further surgical intervention. While GISTs typically benefit from surgery and tyrosine kinase inhibitors (TKIs), those with SDHB-loss are resistant to TKIs, requiring a different management approach. This case emphasizes the importance of surgical intervention for SDHB-deficient GISTs and the need for ongoing research into effective treatments for this subtype.

Pan-Canadian consensus recommendations for GIST management in high- and low-throughput centres across Canada

Gastrointestinal stromal tumours (GISTs) are mesenchymal tumours that originate from the interstitial cells of Cajal. GISTs are mainly driven by gain-of-function mutations in receptor tyrosine kinase or platelet-derived growth factor receptor alpha. Surgical resection is the only curative treatment for localized tumours and all currently approved medical GIST treatments are based on orally available tyrosine kinase inhibitors. Recent discoveries in the molecular and clinical features of GISTs have greatly impacted GIST management. Due to the provincially rather than nationally administered Canadian healthcare system, there have been inconsistencies in the treatment of GISTs across the country. Therefore, guidance on the latest knowledge, clinical management and treatment of GIST is needed to standardize the approach to GIST management nationwide. To establish pan-Canadian guidance, provide up-to-date data and harmonize the clinical practice of GIST management in high- and low-throughput centres across Canada; a panel of 20 physicians with extensive clinical experience in GIST management reviewed relevant literature. This included radiologists, pathologists, interventional radiologists, surgeons and medical oncologists across Canada. The structured literature focused on seven key domains: molecular profiling, radiological techniques/reporting, targeted localized therapy, intricacies of systemic treatments, emerging tests, multidisciplinary care and patient advocacy. This literature review, along with clinical expertise and opinion, was used to develop this concise and clinically relevant consensus paper to harmonize the knowledge and clinical practice on GIST management across Canada. The content presented here will help guide healthcare providers, especially in Canada, in terms of approaching and managing GIST.

English version of Japanese Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) issued by the Japan Society of Clinical Oncology

The Japan Society of Clinical Oncology Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) have been published in accordance with the Minds Manual for Guideline Development 2014 and 2017. A specialized team independent of the working group for the revision performed a systematic review. Since GIST is a rare type of tumor, clinical evidence is not sufficient to answer several clinical and background questions. Thus, in these guidelines, we considered that consensus among the experts who manage GIST, the balance between benefits and harms, patients' wishes, medical economic perspective, etc. are important considerations in addition to the evidence. Although guidelines for the treatment of GIST have also been published by the National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO), there are some differences between the treatments proposed in those guidelines and the treatments in the present guidelines because of the differences in health insurance systems among countries.

Genetic Predisposition to Sarcoma: What Should Clinicians Know?

OPINION STATEMENT

Pathogenic germline variants in the setting of several associated cancer predisposition syndromes (CPS) may lead to the development of sarcoma. We would consider testing for a CPS in patients with a strong family history of cancer, multiple primary malignancies, and/or pediatric/adolescent/young adult patients diagnosed with other malignancies strongly associated with CPS. When a CPS is diagnosed in a patient with sarcoma, additional treatment considerations and imaging options for those patients are required. This applies particularly to the use of radiation therapy, ionizing radiation with diagnostic imaging, and the use of alkylating chemotherapy. As data and guidelines are currently lacking for many of these scenarios, we have adopted a shared decision-making process with patients and their families. If the best chance for cure in a patient with CPS requires utilization of radiation therapy or alkylating chemotherapy, we discuss the risks with the patient but do not omit these modalities. However, if there are treatment options that yield equivalent survival rates, yet avoid these modalities, we elect for those options. Considering staging imaging and post-therapy evaluation for sarcoma recurrence, we avoid surveillance techniques that utilize ionizing radiation when possible but do not completely omit them when their use is indicated.

Combined Germline and Mosaic SDHA Mutation Is Associated With a Multicancer Syndrome Including Neuroblastoma, Renal Cancer, and Multifocal GI Tumor

Highlighting here a patient case with neuroblastoma, renal cancer & GIST from germline SDHA.

Prevalence and prognosis of hypoxia-inducible factor-2α (HIF-2α) pathway gene mutations across advanced solid tumors

INTRODUCTION

Hypoxia-inducible factor-2α (HIF-2α) modulates the hypoxic response pathway in tumors; however, mutations in pathways (including SDHA, SDHB, SDHC, SDHD, FH, and VHL genes) that are suspected to activate HIF-2α are poorly understood, with limited understanding of the prevalence and clinical prognosis.

METHODS

This retrospective observational study used a de-identified nationwide (US-based) clinico-genomic database (CGDB) across 15 available tumor types.

RESULTS

Among the 9467 adult patients with advanced/metastatic solid tumors included in the analysis, any mutation at the above-mentioned six genes was observed in 1.8% (95% CI: 1.5-2.1) of patients. The mutation prevalence ranged from 0.05% of SDHD to 0.93% of VHL. When further stratified by tumor type, the prevalence of gene mutation in each tumor type was well below 1%, except for VHL with 44% in renal cell carcinomas (RCC). Excluding RCC, the prevalence of any HIF-2α gene mutations in the study population was 0.9% (95% CI: 0.8-1.2). The median overall survival (OS) from 1 and 2 L therapy among patients with any HIF-2α gene mutation was 14.5 (95% CI: 11.5-24.2) and 9.3 (95% CI: 6.0-18.1) months, respectively, compared with 13.4 (95% CI: 12.9-13.9) and 9.8 (95% CI: 9.3-10.4) months among patients without HIF-2α gene mutations.

DISCUSSION AND CONCLUSIONS

The prevalence of HIF-2α related gene mutations was generally low (<1%) across the 15 solid tumor types, except for VHL in RCC. No significant association between HIF-2α gene mutation status and OS was identified among patients evaluated in this study.

Gastrointestinal Malignancy: Genetic Implications to Clinical Applications

Advances in molecular genetics have revolutionized our understanding of the pathogenesis, progression, and therapeutic options for treating gastrointestinal (GI) cancers. This chapter provides a comprehensive overview of the molecular landscape of GI cancers, focusing on key genetic alterations implicated in tumorigenesis across various anatomical sites including GIST, colon and rectum, and pancreas. Emphasis is placed on critical oncogenic pathways, such as mutations in tumor suppressor genes, oncogenes, chromosomal instability, microsatellite instability, and epigenetic modifications. The role of molecular biomarkers in predicting prognosis, guiding treatment decisions, and monitoring therapeutic response is discussed, highlighting the integration of genomic profiling into clinical practice. Finally, we address the evolving landscape of precision oncology in GI cancers, considering targeted therapies and immunotherapies.

Hereditary succinate dehydrogenase-deficient renal cell carcinoma

Succinate dehydrogenase (SDH), formed by four subunits SDHA, SDHB, SDHC, SDHD, and an assembly factor SDHAF2, functions as a key respiratory enzyme. Biallelic inactivation of genes encoding any of the components, almost always in the presence of a germline mutation, causes loss of function of the entire enzyme complex (so-called SDH deficiency) and subsequent development of SDH-deficient neoplasms which include pheochromocytoma/paraganglioma, gastrointestinal stromal tumor, and renal cell carcinoma (RCC). These tumors may occur in the same patient or kindred. SDH-deficient RCC shows distinctive morphological features with vacuolated eosinophilic cytoplasm due to distinctive cytoplasmatic inclusions containing flocculent material. The diagnosis is confirmed by loss of SDHB on immunohistochemistry with positive internal control. The majority of tumors occur in the setting of germline mutations in one of the SDH genes, most commonly SDHB. The prognosis is excellent for low-grade tumors but worse for high-grade tumors with high-grade nuclei, sarcomatoid change, or coagulative necrosis. Awareness of the morphological features and low-threshold for applying SDHB immunohistochemistry help identify patients with SDH-deficient RCC and hereditary SDH-deficient tumor syndromes. In this review we summarize recent development on the clinical and genetic features, diagnostic approach, and pitfalls of SDH-deficient syndrome, focusing on SDH-deficient renal cell carcinomas.

Preferential MGMT hypermethylation in SDH-deficient wild-type GIST

AIMS

Wild-type gastrointestinal stromal tumours (wtGIST) are frequently caused by inherited pathogenic variants, or somatic alterations in the succinate dehydrogenase subunit genes (SDHx). Succinate dehydrogenase is a key enzyme in the citric acid cycle. SDH deficiency caused by SDHx inactivation leads to an accumulation of succinate, which inhibits DNA and histone demethylase enzymes, resulting in global hypermethylation. Epigenetic silencing of the DNA repair gene MGMT has proven utility as a positive predictor of the therapeutic efficacy of the alklyating drug temozolomide (TMZ) in tumours such as glioblastoma multiforme. The aim of this study was to examine MGMT promoter methylation status in a large cohort of GIST.

METHODS

MGMT methylation analysis was performed on 65 tumour samples including 47 wtGIST (33 SDH-deficient wtGIST and 11 SDH preserved wtGIST) and 21 tyrosine kinase (TK) mutant GIST.

RESULTS

MGMT promoter methylation was detected in 8 cases of SDH-deficient (dSDH) GIST but in none of the 14 SDH preserved wild-type GIST or 21 TK mutant GIST samples analysed. Mean MGMT methylation was significantly higher (p 0.0449) and MGMT expression significantly lower (p<0.0001) in dSDH wtGIST compared with TK mutant or SDH preserved GIST. No correlation was identified between SDHx subunit gene mutations or SDHC epimutation status and mean MGMT methylation levels.

CONCLUSION

MGMT promoter hypermethylation occurs exclusively in a subset of dSDH wtGIST. Data from this study support testing of tumour MGMT promoter methylation in patients with dSDH wtGIST to identify those patients who may benefit from most from TMZ therapy.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Research progress on the pathogenesis of the SDHB mutation and related diseases

With the improvement of genetic testing technology in diseases in recent years, researchers have a more detailed and clear understanding of the source of cancers. Succinate dehydrogenase B (SDHB), a mitochondrial gene, is related to the metabolic activities of cells and tissues throughout the body. The mutations of SDHB have been found in pheochromocytoma, paraganglioma and other cancers, and is proved to affect the occurrence and progress of those cancers due to the important structural functions. The importance of SDHB is attracting more and more attention of researchers, however, reviews on the structure and function of SDHB, as well as on the mechanism of its carcinogenesis is inadequate. This paper reviews the relationship between SDHB mutations and related cancers, discusses the molecular mechanism of SDHB mutations that may lead to tumor formation, analyzes the mutation spectrum, structural domains, and penetrance of SDHB and sorts out some of the previously discovered diseases. For the patients with SDHB mutation, it is recommended that people in SDHB mutation families undergo regular genetic testing or SDHB immunohistochemistry (IHC). The purpose of this paper is hopefully to provide some reference and help for follow-up researches on SDHB.

Novel Genomic Risk Stratification Model for Primary Gastrointestinal Stromal Tumors (GIST) in the Adjuvant Therapy Era

PURPOSE

Traditional risk stratification schemes in gastrointestinal stromal tumors (GIST) were defined in the pre-imatinib era and rely solely on clinicopathologic metrics. We hypothesize that genomic-based risk stratification is prognostically relevant in the current era of tyrosine kinase inhibitor (TKI) therapeutics.

EXPERIMENTAL DESIGN

Comprehensive mutational and copy-number profiling using MSK-IMPACT was performed. We integrated clinicopathologic and genomic parameters and utilized an elastic-net penalized Cox proportional hazards machine learning model for outcome risk stratification.

RESULTS

A 3-tier genomic risk stratification model for recurrence-free survival (RFS) in 152 primary localized gastric and 80 small bowel GISTs was proposed. Gastric GISTs were classified as high risk if chr1p deletion or SDHB loss was present, and intermediate risk if chr14q deletion was present or KIT exon 11 mutation was absent. Small bowel GISTs were classified as high risk if MAX/MGA/MYC, CDKN2A, or RB1 alterations were present, and intermediate risk if chr1p deletion or chr5q amplification was present. Compared with conventional risk stratification, genomic risk stratification both upgrades and downgrades, suggesting that conventional risk stratification may underestimate or overtreat some high-risk and low-risk patients, respectively. Longitudinal sequencing detected most KIT-independent genomic alterations at baseline. Subanalysis in 26 SDH-deficient GISTs revealed that presence of TP53 mutations or chr1q amplifications portends worse RFS and disease-free survival.

CONCLUSIONS

We developed a novel, next-generation genomic risk stratification model for primary gastric and small bowel GISTs, complementing traditional clinicopathologic models. Future independent validation of our model in external cohorts is essential.

Primary vulvar extragastrointestinal stromal tumor in a 77-year-old woman

Extragastrointestinal stromal tumors (EGISTs) carry the same morphological, immunohistochemical and molecular features as gastrointestinal stromal tumors (GISTs) and involve extragastrointestinal tract soft tissue. The majority of reported EGIST cases arise from intraabdominal, retroperitoneal, or pelvic soft tissue. A significant subset of such tumors originates from the gastrointestinal muscle layer, grows in an exophytic manner, then loses attachment to the gastrointestinal tract. Consequently, true EGISTs are exceedingly rare. Herein, we are reporting a case of a vulvar EGIST. A 77-year-old woman presented with a painless subcutaneous nodule on the right perineum. An excisional biopsy showed a fairly circumscribed bland spindle cell lesion in the dermis. The tumor cells were positive for CD117 and ANO1/DOG-1 and negative for smooth muscle myosin, smooth muscle actin, STAT6, low- and high-molecular-weight cytokeratins, SOX10, MART-1, CD10, S-100 protein, and estrogen and progesterone receptors. A diagnosis of EGIST was made and complete excision was recommended. Superficial/subcutaneous EGISTs are extremely rare, and it is important for dermatopathologists to be aware of this entity as it can be misdiagnosed as more common spindle cell neoplasms, both benign and malignant, including but not limited to smooth muscle neoplasms (leiomyoma/leiomyosarcoma), spindle cell melanoma, and sarcomatoid squamous cell carcinoma.

Emerging Targeted Therapeutic Strategies to Overcome Imatinib Resistance of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common malignant mesenchymal neoplasms of the gastrointestinal tract. The gold standard for the diagnosis of GISTs is morphologic analysis with an immunohistochemical evaluation plus genomic profiling to assess the mutational status of lesions. The majority of GISTs are driven by gain-of-function mutations in the proto-oncogene c-KIT encoding the tyrosine kinase receptor (TKR) known as KIT and in the platelet-derived growth factor-alpha receptor (PDGFRA) genes. Approved therapeutics are orally available as tyrosine kinase inhibitors (TKIs) targeting KIT and/or PDGFRA oncogenic activation. Among these, imatinib has changed the management of patients with unresectable or metastatic GISTs, improving their survival time and delaying disease progression. Nevertheless, the majority of patients with GISTs experience disease progression after 2-3 years of imatinib therapy due to the development of secondary KIT mutations. Today, based on the identification of new driving oncogenic mutations, targeted therapy and precision medicine are regarded as the new frontiers for GISTs. This article reviews the most important mutations in GISTs and highlights their importance in the current understanding and treatment options of GISTs, with an emphasis on the most recent clinical trials.

The Recent Advances in Molecular Diagnosis of Soft Tissue Tumors

Soft tissue tumors are rare mesenchymal tumors with divergent differentiation. The diagnosis of soft tissue tumors is challenging for pathologists owing to the diversity of tumor types and histological overlap among the tumor entities. Present-day understanding of the molecular pathogenesis of soft tissue tumors has rapidly increased with the development of molecular genetic techniques (e.g., next-generation sequencing). Additionally, immunohistochemical markers that serve as surrogate markers for recurrent translocations in soft tissue tumors have been developed. This review aims to provide an update on recently described molecular findings and relevant novel immunohistochemical markers in selected soft tissue tumors.

SDHA Germline Mutations in SDH-Deficient GISTs: A Current Update

Loss of function of the succinate dehydrogenase complex characterizes 20–40% of all KIT/PDGFRA-negative GIST. Approximately half of SDH-deficient GIST patients lack SDHx mutations and are caused by a hypermethylation of the SDHC promoter, which causes the repression of SDHC transcription and depletion of SDHC protein levels through a mechanism described as epimutation. The remaining 50% of SDH-deficient GISTs have mutations in one of the SDH subunits and SDHA mutations are the most common (30%), with consequent loss of SDHA and SDHB protein expression immunohistochemically. SDHB, SDHC, and SDHD mutations in GIST occur in only 20–30% of cases and most of these SDH mutations are germline. More recently, germline mutations in SDHA have also been described in several patients with loss of function of the SDH complex. SDHA-mutant patients usually carry two mutational events at the SDHA locus, either the loss of the wild type allele or a second somatic event in compound heterozygosis. This review provides an overview of all data in the literature regarding SDHA-mutated GIST, especially focusing on the prevalence of germline mutations in SDH-deficient GIST populations who harbor SDHA somatic mutations, and offers a view towards understanding the importance of genetic counselling for SDHA-variant carriers and relatives.

Back to Biochemistry: Evaluation for and Prognostic Significance of SDH Mutations in Paragangliomas and Pheochromocytomas

There is increasing recognition of the high prevalence of hereditary predisposition syndromes in patients diagnosed with paraganglioma/pheochromocytoma. It is widely acknowledged that germline pathogenic alterations of the succinate dehydrogenase complex genes (SDHA, SDHB, SDHC, SDHD, SDHAF2) contribute to the pathogenesis of most of these tumors. Herein, we have provided an update on the biology and diagnosis of succinate dehydrogenase-deficient paraganglioma/pheochromocytoma, including the molecular biology of the succinate dehydrogenase complex, mechanisms and consequences of inactivation of this complex, the prevalence of pathogenic alterations, and patterns of inheritance.

Dataset for reporting of gastrointestinal stromal tumours: recommendations from the International Collaboration on Cancer Reporting (ICCR)

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the gastrointestinal tract and are among the most frequent sarcomas. Accurate diagnosis, classification, and reporting are critical for prognostication and patient management, including selection of appropriate targeted therapy. Here we report on international consensus-based datasets for the pathology reporting of biopsy and resection specimens of GIST. The datasets were produced under the auspices of the International Collaboration on Cancer Reporting (ICCR), a global alliance of major international pathology and cancer organizations. An international expert panel consisting of pathologists, a surgical oncologist, and a medical oncologist produced a set of core and noncore data items for biopsy and resection specimens based on a critical review and discussion of current evidence. All professionals involved were subspecialized soft tissue tumour experts and affiliated with tertiary referral centres. Commentary was provided for each data item to explain its clinical relevance and the rationale for selection as a core or noncore element. Following international public consultation, the datasets, which include synoptic reporting guides, were finalized and ratified, and published on the ICCR website. These first international datasets for GIST are intended to promote high-quality, standardised pathology reporting. Their widespread adoption will improve consistency of reporting, facilitate multidisciplinary communication, and enhance comparability of data, all of which will ultimately help to improve the management of patients with GIST. All the ICCR datasets, including these on GIST, are freely available worldwide on the ICCR website (www.iccr-cancer.org/datasets).

TKI Treatment Sequencing in Advanced Gastrointestinal Stromal Tumors

Prior to the early 2000s, patients with advanced gastrointestinal stromal tumors (GIST) had very poor prognoses owing to a lack of effective therapies. The development of tyrosine kinase inhibitors at the turn of the century significantly improved the overall survival for patients with GIST. The resounding success of imatinib in the first clinical trial of a tyrosine kinase inhibitor to treat GIST led to its approval for first-line therapy for advanced GIST; this study was open to all comers and not restricted to any GIST subtype(s). The trials that led to the approvals of second-, third-, and fourth-line therapy for advanced GIST were also open to all patients with advanced/metastatic GIST. Only in retrospect do we realize the role that the molecular subtypes played in the results observed in these studies. In this review, we discuss the studies that led to the US Food and Drug Administration approval of imatinib (first line), sunitinib (second line), regorafenib (third line), and ripretinib (fourth line) for advanced KIT-mutant GIST. In addition, we review how information about GIST molecular subtypes has been used to accelerate the approval of other targeted therapies for non-KIT mutant GIST, leading to the approval of five additional drugs indicated for the treatment of specific GIST molecular subtypes. We also discuss how our understanding of the molecular subtypes will play a role in the next generation of therapeutic approaches for treating advanced GIST.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

Tumorigenesis Mechanisms Found in Hereditary Renal Cell Carcinoma: A Review

Renal cell carcinoma is a heterogenous cancer composed of an increasing number of unique subtypes each with their own cellular and tumor behavior. The study of hereditary renal cell carcinoma, which composes just 5% of all types of tumor cases, has allowed for the elucidation of subtype-specific tumorigenesis mechanisms that can also be applied to their sporadic counterparts. This review will focus on the major forms of hereditary renal cell carcinoma and the genetic alterations contributing to their tumorigenesis, including von Hippel Lindau syndrome, Hereditary Papillary Renal Cell Carcinoma, Succinate Dehydrogenase-Deficient Renal Cell Carcinoma, Hereditary Leiomyomatosis and Renal Cell Carcinoma, BRCA Associated Protein 1 Tumor Predisposition Syndrome, Tuberous Sclerosis, Birt-Hogg-Dubé Syndrome and Translocation RCC. The mechanisms for tumorigenesis described in this review are beginning to be exploited via the utilization of novel targets to treat renal cell carcinoma in a subtype-specific fashion.

Dutch Gastrointestinal Stromal Tumor (GIST) Registry Data Comparing Sunitinib with Imatinib Dose Escalation in Second-Line Advanced Non-KIT Exon 9 Mutated GIST Patients

Background

The prognosis of patients with advanced gastrointestinal stromal tumor (GIST) has improved greatly after the introduction of imatinib. However, primary or secondary resistance to imatinib occurs in the majority of patients. Sunitinib is the standard second line treatment in exon-9 mutated GIST.

Objective

We compared the clinical outcomes of sunitinib with imatinib dose escalation in patients with progressive advanced non-KIT exon 9 mutated GIST after failure of first line imatinib.

Patients and Methods

A retrospective study was performed, retrieving data from a real-life database (Dutch GIST Registry) including patients with GIST treated with sunitinib or imatinib dose escalation after failure on first line imatinib 400 mg daily. Primary outcome measures were progression free survival (PFS) and overall survival (OS).

Results

In total, 110 patients were included, 72 (65.5%) patients were treated with sunitinib (group A) and 38 (34.5%) received an imatinib dose escalation (group B). Important prognostic features at baseline, such as tumor size, stage at diagnosis, mitotic count and localization were equally distributed in both groups. No significant difference (p = 0.88) between median PFS in group A [8.7 months (95% CI 5.6–11.3)] and group B [5.6 months, (95% CI 2.6–8.7)] was observed. Moreover, the OS was similar between group A and group B; 63.2 months and 63.4 months, respectively.

Conclusion

This study represents a proper sample size cohort containing detailed data on mutational status of patients with advanced GIST. We illustrated that imatinib dose escalation could serve as a good alternative for sunitinib as second-line treatment in patients with a non-KIT exon 9 mutation.

NCCN Guidelines® Insights: Gastrointestinal Stromal Tumors, Version 2.2022

Gastrointestinal stromal tumors (GIST) are the most common type of soft tissue sarcoma that occur throughout the gastrointestinal tract. Most of these tumors are caused by oncogenic activating mutations in the KIT or PDGFRA genes. The NCCN Guidelines for GIST provide recommendations for the diagnosis, evaluation, treatment, and follow-up of patients with these tumors. These NCCN Guidelines Insights summarize the panel discussion behind recent important updates to the guidelines, including revised systemic therapy options for unresectable, progressive, or metastatic GIST based on mutational status, and updated recommendations for the management of GIST that develop resistance to specific tyrosine kinase inhibitors.

Lymph Node Metastases in Gastrointestinal Stromal Tumors: an Uncommon Event

BACKGROUND

Lymph node (LN) metastases are uncommon among gastrointestinal stromal tumors (GISTs), and their presence has not been utilized in disease prognostication. This study was designed to examine factors associated with GIST nodal metastases and their impact on survival.

PATIENTS AND METHODS

Patients undergoing surgical resection of GIST with nodal evaluation were selected from the National Cancer Database. Logistic regression was utilized to evaluate factors associated with LN metastases. Survival was assessed for patients with and without nodal involvement and Cox regression was used to evaluate the impact of LN metastases while adjusting for other prognostic factors.

RESULTS

Out of 5018 patients, 301 (6.0%) had LN involvement. Nodal metastases occurred most frequently among tumors of the stomach (49.5%), followed by the small bowel (43.2%), colorectum (6.0%), and esophagus (1.3%). On multivariable analysis, male sex (OR 1.34), high mitotic rate (OR 2.10), tumor size (OR 1.02), and a primary tumor located in the small bowel (OR 1.36) were all significantly associated with nodal metastases. LN metastases were significantly associated with decreased overall survival (OS) for tumors arising in the small bowel (log-rank p < 0.01) and the colorectum (log-rank p < 0.01). Within a multivariable model adjusting for established prognostic factors, LN metastases remained independently associated with decreased survival (HR 1.60, p < 0.001).

CONCLUSIONS

For GISTs, LN metastases occur more often in males and were associated with tumor size and mitotic activity. Nodal involvement is associated with decreased survival, independent of other well-established prognostic factors.

Angiogenesis in gastrointestinal stromal tumors: From bench to bedside

Gastrointestinal stromal tumors (GISTs) are rare neoplasms with an estimated incidence from 0.78 to 1-1.5 patients per 100000. They most commonly occur in the elderly during the eighth decade of life affecting predominantly the stomach, but also the small intestine, the omentum, mesentery and rectosigmoid. The available treatments for GIST are associated with a significant rate of recurrent disease and adverse events. Thorough understanding of GIST’s pathophysiology and translation of this knowledge into novel regimens or drug repurposing is essential to counter this challenge. The present review summarizes the existing evidence about the role of angiogenesis in GIST’s development and progression and discusses its clinical underpinnings.

An exploration in pitfalls in interpreting SDHB immunohistochemistry

AIMS

Mutations and epimutations in genes encoding the succinate dehydrogenase complex (SDHx) are associated with multiple tumor types in which identification of SDH-deficiency has significant management implications. Immunohistochemistry (IHC) for the SDHB subunit can help detect SDH-deficiency, which manifests as complete loss of staining in tumor cells. However, a subset of SDH-deficient tumors can show aberrant cytoplasmic SDHB-IHC staining patterns and be misinterpreted as "retained," a diagnostic pitfall complicating interpretation. Herein, we characterize in detail aberrant SDHB-IHC staining patterns in SDH-deficient tumors.

METHODS AND RESULTS

We identified 23 tumors from patients with known germline SDHx and/or molecularly confirmed SDHx pathogenic/likely-pathogenic variants in their tumor. Of these, 8 (35%) showed significant SDHB-IHC staining: 1 SDHA-, 1 SDHB-, 3 SDHC- and 3 SDHD-mutated cases. In all 8 cases, closer inspection revealed differences in intensity and intracellular distribution of SDHB-IHC staining in tumor cells compared to adjacent nonneoplastic cells: nonneoplastic cells showed intense cytoplasmic coarse granular staining; tumor cells in 7/8 cases showed weak to focally strong, cytoplasmic blush to fine granular staining, in >80% of cells. The remaining case on initial block showed variably strong nongranular cytoplasmic staining with globular perinuclear accentuation throughout, only subtly distinct from staining pattern of nonneoplastic cells. SDHB-IHC performed on two additional blocks in this latter case revealed significant intratumoral heterogeneity including convincing areas of complete loss.

CONCLUSIONS

When evaluating SDHB-IHC, care should be taken to distinguish true retained expression from aberrant cytoplasmic expression, which may be difficult to appreciate. Sometimes this may require additional molecular testing.

The GIST of Advances in Treatment of Advanced Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common malignant neoplasm of mesenchymal origin and a compelling clinical and biologic model for the rational development of molecularly targeted agents. This is because the majority of GISTs are driven by gain-of-function mutations in KIT or PDGFRA receptor tyrosine kinases. Specific GIST mutations circumscribe well-defined molecular subgroups that must be determined during the diagnostic work-up to guide clinical management, including therapeutic decisions. Surgery is the cornerstone treatment in localized disease and can also be clinically relevant in the metastatic setting. The correct combination and sequence of targeted agents and surgical procedures improves outcomes for patients with GIST and should be discussed individually within multidisciplinary expert teams. All currently approved agents for the treatment of GIST are based on orally available tyrosine kinase inhibitors targeting KIT and PDGFRA oncogenic activation. Although first-line imatinib achieves remarkable prolonged disease control, the benefit of subsequent lines of treatment is more modest. Novel therapeutic strategies focus on overcoming the heterogeneity of KIT or PDGFRA secondary mutations and providing more potent inhibition of specific challenging mutations. This article reviews the current understanding and treatment of GIST, with an emphasis on recent advances.

New treatment strategies for advanced-stage gastrointestinal stromal tumours

When gastrointestinal stromal tumour (GIST), the most common form of sarcoma, was first recognized as a distinct pathological entity in the 1990s, patients with advanced-stage disease had a very poor prognosis owing to a lack of effective medical therapies. The discovery of KIT mutations as the first and most prevalent drivers of GIST and the subsequent development of the first KIT tyrosine kinase inhibitor (TKI), imatinib, revolutionized the treatment of patients with this disease. We can now identify the driver mutation in 99% of patients with GIST via molecular diagnostic testing, and therapies have been developed to treat many, but not all, molecular subtypes of the disease. At present, seven drugs are approved by the FDA for the treatment of advanced-stage GIST (imatinib, sunitinib, regorafenib, ripretinib, avapritinib, larotrectinib and entrectinib), all of which are TKIs. Although these agents can be very effective for treating certain GIST subtypes, challenges remain and new therapeutic approaches are needed. In this Review, we discuss the molecular subtypes of GIST and the evolution of current treatments, as well as their therapeutic limitations. We also highlight emerging therapeutic approaches that might overcome clinical challenges through novel strategies predicated on the biological features of the distinct GIST molecular subtypes.

Patient demographics, clinicopathologic features, and outcomes in wild-type gastrointestinal stromal tumor: a national cohort analysis

Wild-type KIT and PDGFRA gastrointestinal stromal tumors (GIST) are rare tumors with limited treatment options. We sought to determine the clinicopathologic features of wild-type GIST and identify factors that influence overall survival (OS) using a large national database. Retrospective evaluation of patients with wild-type GIST in the National Cancer Database (NCDB) was performed. Demographic, clinicopathologic, and treatment data were analyzed. Features associated with OS were investigated using Kaplan-Meier analysis and Cox proportional hazards model. 244 patients with median diagnosis age of 59 years (95% CI 57-63) were identified. The stomach was the most common primary site (57%) followed by the small intestine (35%). Surgical resection was performed on 85% of patients and 53% of patients received systemic therapy. Factors associated with decreased OS on multivariable analysis included small intestine primary (HR 2.72, 95% CI 1.13-6.69, P = 0.026) and > 5 mitoses per 50 HPF (HR 4.77, 95% CI 1.86-13.2, P = 0.001). Wild-type GISTs may be identified in older patients, with most arising in the stomach and small bowel. Surgery remains the principal treatment modality. Small intestine primary site and high mitotic count were associated with abbreviated OS.

Characterization of Aberrations in DNA Damage Repair Pathways in Gastrointestinal Stromal Tumors: The Clinicopathologic Relevance of γH2AX and 53BP1 in Correlation with Heterozygous Deletions of CHEK2, BRCA2, and RB1

Genetic aberrations involving DNA damage repair (DDR) remain underexplored in gastrointestinal stromal tumors (GISTs). We characterized DDR abnormalities using targeted next-generation sequencing and multiplex ligation-dependent probe amplification, and performed immunofluorescence (IF) and immunohistochemistry (IHC) analyses of γH2AX and 53BP1. Consistent with IF-validated nuclear co-localization, γH2AX and 53BP1 showed robust correlations in expression levels, as did both biomarkers between IF and IHC. Without recurrent pathogenic single-nucleotide variants, heterozygous deletions (HetDels) frequently targeted DNA damage-sensing genes, with CHEK2-HetDel being the most prevalent. Despite their chromosomal proximity, BRCA2 and RB1 were occasionally hit by HetDels and were seldom co-deleted. HetDels of CHEK2 and BRCA2 showed a preference for older age groups, while RB1-HetDel predominated in the non-gastric, high-risk, and 53BP1-overexpressing GISTs. Higher risk levels were consistently related to γ-H2AX or 53BP1 overexpression (all p < 0.01) in two validation cohorts, while only 53BP1 overexpression was associated with the deletion of KIT exon 11 (KITex11-del) among genotyped GISTs. Low expressers of dual biomarkers were shown by univariate analysis to have longer disease-free survival (p = 0.031). However, higher risk levels, epithelioid histology, and KITex11-del retained prognostic independence. Conclusively, IHC is a useful surrogate of laborious IF in the combined assessment of 53BP1 and γ-H2AX to identify potential DDR-defective GISTs, which were frequently aberrated by HetDels and a harbinger of progression.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

Oncometabolites as Regulators of DNA Damage Response and Repair

Dysregulation of DNA damage response and repair (DDR) contributes to oncogenesis, yet also generates the potential for targeted cancer therapies by exploiting synthetic lethal interactions. Oncometabolites, small intermediates of metabolism overproduced in certain cancers, have emerged as a new mechanism of DDR modulation through their effects on multiple DNA repair pathways. Increasing evidence suggests that oncometabolite-induced DDR defects may offer the opportunity for tumor-selective chemo- and radio-sensitization. Here we review the biology of oncometabolites and diverse mechanisms by which they impact DDR, with a focus on emerging therapeutic strategies and ongoing clinical trials targeting oncometabolite-induced DDR defects in cancer.

Molecular Pathogenesis of Gastrointestinal Stromal Tumor: A Paradigm for Personalized Medicine

Over the past three to four decades, the molecular pathogenesis of gastrointestinal stromal tumors (GISTs) has been elucidated in great detail. In this review, we discuss the biological genesis of GISTs, identification of the various primary activating driver mutations (focusing on KIT and PDGFRA), oncogene addiction and targeted therapies with imatinib and other tyrosine kinase inhibitors, and the subsequent characterization of the various mechanisms of drug resistance. We illustrate how GIST has become a quintessential paradigm for personalized medicine. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A proposed risk assessment score for gastrointestinal stromal tumors based on evaluation of 19,030 cases from the National Cancer Database

BACKGROUND

Standard risk assessment algorithms for gastrointestinal stromal tumor (GIST) are based on anatomic and histopathological variables with arbitrarily defined subcategories. Our goal was to improve risk assessment for GIST through retrospective analysis of patient data.

METHODS

The National Cancer Database (NCDB) was queried for patients with GIST; the final cohort consisted of 19,030 cases. Main outcomes were metastasis at presentation and overall survival. A test dataset was used to reevaluate risk stratification parameters in multivariate regression models. A novel risk assessment system was applied to the validation dataset and compared to other currently used risk assessment schemes.

RESULTS

Analysis of observed prevalence of metastases at presentation suggested 7 cm and mitotic rates > 10 per 5 mm² as optimal threshold values. A proposed risk stratification score showed statistical superiority compared to the National Comprehensive Cancer Network, American Joint Committee on Cancer, and modified National Institute of Health classifications in predicting probability of presentation with metastasis at diagnosis and 4-year overall survival after accounting for important covariables including patient age and comorbidities, year of diagnosis, and surgical/systemic therapeutic regimen.

CONCLUSIONS

Reexamination of prognostic factors for GIST demonstrated that current threshold values for tumor size and mitotic rate are suboptimal. A risk stratification score based on revised categorization of these factors outperformed currently used risk assessment algorithms.

DOG1 expression is common in human tumors: A tissue microarray study on more than 15,000 tissue samples

DOG1 (Discovered on GIST1) is a voltage-gated calcium-activated chloride and bicarbonate channel that is highly expressed in interstitial cells of Cajal and in gastrointestinal stromal tumors (GIST) derived from Cajal cells. To systematically determine in what tumor entities and normal tissue types DOG1 may be further expressed, a tissue microarray (TMA) containing 15,965 samples from 121 different tumor types and subtypes as well as 608 samples of 76 different normal tissue types was analyzed by immunohistochemistry. DOG1 immunostaining was found in 67 tumor types including GIST (95.7%), esophageal squamous cell carcinoma (31.9%), pancreatic ductal adenocarcinoma (33.6%), adenocarcinoma of the Papilla Vateri (20%), squamous cell carcinoma of the vulva (15.8%) and the oral cavity (15.3%), mucinous ovarian cancer (15.3%), esophageal adenocarcinoma (12.5%), endometrioid endometrial cancer (12.1%), neuroendocrine carcinoma of the colon (11.1%) and diffuse gastric adenocarcinoma (11%). Low level-DOG1 immunostaining was seen in 17 additional tumor entities. DOG1 expression was unrelated to histopathological parameters of tumor aggressiveness and/or patient prognosis in cancers of the breast (n = 1002), urinary bladder (975), ovary (469), endometrium (173), stomach (233), and thyroid gland (512). High DOG1 expression was linked to estrogen receptor expression in breast cancer (p < 0.0001) and absence of HPV infection in squamous cell carcinomas (p = 0.0008). In conclusion, our data identify several tumor entities that can show DOG1 expression levels at similar levels as in GIST. Although DOG1 is tightly linked to a diagnosis of GIST in spindle cell tumors, the differential diagnosis is much broader in DOG1 positive epithelioid neoplasms.

Clinicopathological value of long non-coding RNA profiles in gastrointestinal stromal tumor

Background

Long non-coding RNAs (lncRNAs) have been implicated in diagnosis and prognosis in various cancers. However, few lncRNA signatures have been established for prediction of gastrointestinal stromal tumors (GIST). We aimed to explore a lncRNA signature profile that associated with clinical relevance by mining data from Gene Expression Ominus (GEO) and Surveillance, Epidemiology, and End Results (SEER) Program.

Methods

Using a lncRNA-mining approach, we performed non-negative matrix factorization (NMF) consensus algorithm in Gastrointestinal stromal tumors (GISTs) cohorts (61 patients from GSE8167 and GSE17743) to cluster LncRNA expression profiles. Comparative markers selection, and Gene Set Enrichment Analysis (GSEA) algorithm were performed between distinct molecular subtypes of GIST. The survival rate of GIST patients from SEER stratified by gender were compared by Kaplan-Meier method and log-rank analysis. lncRNA-mRNA co-expression analysis was performed by Pearson correlation coefficients (PCC) using R package LINC. Somatic copy number alterations of GIST patients (GSE40966) were analyzed via web server GenePattern GISTIC2 algorithm.

Results

A total of four lncRNA molecular subtypes of GIST were identified with distinct biological pathways and clinical characteristics. LncRNA expression profiles well clustered the GIST samples into small size (<5 mm) and large size tumors (>5 mm), which is a fundamental index for GIST malignancy diagnosis. Several lncRNAs with abundant expression (LRRC75A-AS1, HYMAI, NEAT1, XIST and FTX) were closely associated with tumor size, which may suggest to be biomarkers for the GIST malignancy. Particularly, LRRC75A-AS1 was positively associated with tumor diameters and suggested an oncogene in GIST. Co-expression analysis suggested that chromosome region 17p11.2-p12 may contribute to the oncogenic process in malignant GIST. Interestingly, the gender had a strong influence on clustering by lncRNA expression profile. Data from the Surveillance, Epidemiology, and End Results (SEER) Program were further explored and 7983 patients who were diagnosed with GISTs from 1973 to 2014 were enrolled for analysis. The results also showed the favorable prognosis for female patients. The survival rate between male and female with GIST was statistically significant (P < 0.0001). Gene set enrichment analysis (GSEA) indicated distinct pathways between female and male, and malignant GIST was associated with several cancer metabolism and cell cycle associated pathways.

Conclusions

This lncRNAs-based classification for GISTs may provide a molecular classification applicable to individual GIST that has implications to influence lncRNA markers selection and prediction of tumor progression.

SDHC Methylation Pattern in Patients With Carney Triad

Carney triad is a multitumor syndrome affecting almost exclusively young women in a nonfamilial setting, which manifests by multifocal gastric gastrointestinal stromal tumors, paragangliomas, and pulmonary chondroma. The Carney triad-associated tumors are characterized by a deficiency of the mitochondrial succinate dehydrogenase enzymatic complex. Recently, it has been observed that the deficiency results from epigenetic silencing of the SDHC gene by its promoter hypermethylation. To elucidate anatomic distribution of SDHC promoter methylation in Carney triad patients and thus to shed some light on the possible natural development of this epigenetic change, both neoplastic and available non-neoplastic tissues of 3 patients with Carney triad were tested for hypermethylation at the SDHC promoter site. SDHC promoter hypermethylation was proven in all tumors studied. Lack of SDHC epigenetic silencing in the non-neoplastic lymphoid and duodenal tissue (ie, tissues not involved in the development of Carney triad-associated tumors) together with the finding of SDHC promoter hypermethylation in the non-neoplastic gastric wall favors the hypothesis of postzygotic somatic mosaicism as the biological background of Carney triad; it also offers an explanation of the multifocality of gastrointestinal stromal tumors of the stomach occurring in this scenario as well. However, the precise mechanism responsible for the peculiar organ-specific distribution of Carney triad-associated tumors is still unknown.

Beyond the Driver Mutation: Immunotherapies in Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are a subtype of soft tissue sarcoma (STS), and have become a concept of oncogenic addiction and targeted therapies.The large majority of these tumors develop after a mutation in KIT or platelet derived growth factor receptor α (PDGFRα), resulting in uncontrolled proliferation. GISTs are highly sensitive to imatinib. GISTs are immune infiltrated tumors with a predominance of tumor-associated macrophages (TAMs) and T-cells, including many CD8+ T-cells, whose numbers are prognostic. The genomic expression profile is that of an inhibited Th1 response and the presence of tertiary lymphoid structures and B cell signatures, which are known as predictive to response to ICI. However, the microtumoral environment has immunosuppressive attributes, with immunosuppressive M2 macrophages, overexpression of indoleamine 2,3-dioxygenase (IDO) or PD-L1, and loss of major histocompatibility complex type 1. In addition to inhibiting the KIT oncogene, imatinib appears to act by promoting cytotoxic T-cell activity, interacting with natural killer cells, and inhibiting the expression of PD-L1. Paradoxically, imatinib also appears to induce M2 polarization of macrophages. There have been few immunotherapy trials with anti-CTLA-4 or anti-PD-L1drugs and available clinical data are not very promising. Based on this comprehensive analysis of TME, we believe three immunotherapeutic strategies must be underlined in GIST. First, patients included in clinical trials must be better selected, based on the identified driver mutation (such as PDGFRα D842V mutation), the presence of tertiary lymphoid structures (TLS) or PD-L1 expression. Moreover, innovative immunotherapeutic agents also provide great interest in GIST, and there is a strong rationale for exploring IDO targeting after disease progression during imatinib therapy. Finally and most importantly, there is a strong rationale to combine of c-kit inhibition with immune checkpoint inhibitors.

Kidney cancer: from genes to therapy

Renal cell carcinoma incidence is rising worldwide with increasing subtype stratification by the World Health Organization. Each subtype has unique genetic alterations, cell biology changes and clinical findings. Such genetic alterations offer the potential for individualized therapeutic approaches that are rapidly progressing. This review highlights the most common subtypes of renal cell carcinoma, including both hereditary and sporadic forms, with a focus on genetic changes, clinical findings and ongoing clinical trials.

Succinate dehydrogenase-deficient gastrointestinal stromal tumor: from diagnostic dilemma to novel personalised therapy in 2 case reports

Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumor (GIST) is a unique and distinctive subtype of gastric GIST. The literature on this subtype from developing countries is exceedingly sparse. Patients with SDH-deficient GIST often experience a lack or delay in genomic profiling, despite stereotypical clinicopathologic features, potentially resulting in sub-optimal management. SDH-deficient GISTs are highly syndromic, typically have more indolent behavior, a prognosis not predicted by size and mitotic rate, a tendency to lymph node metastases, and are insensitive to standard tyrosine kinase inhibitors (TKIs). We report two women with SDH-deficient GIST. In the first case, SDH deficiency was identified late due to lack of awareness and poor access to diagnostic facilities. The patient progressed through TKI therapy, but responded to temozolomide, which is under investigation in clinical trials. In the second case, SDH deficiency was identified at diagnosis, and the patient responded well to ¹⁷⁷Lutetium peptide radionuclide receptor therapy (PRRT) after progressing through two lines of TKIs. We aim to highlight the need for more awareness and access to genomic diagnostic facilities for GIST patients, temozolomide as a novel therapy for SDH-deficient GIST, and the potential value of DOTATATE positron emission tomography (PET) and PRRT as a novel imaging modality and therapy for TKI insensitive GIST patients.

Targeted therapy in SDH-deficient GIST

The medical management of advanced gastrointestinal stromal tumors (GIST) has improved with the development of tyrosine kinase inhibitors (TKIs) targeting KIT and PDGFRA mutations. However, approximately 5-10% of GIST lack KIT and PDGFRA mutations, and about a half are deficient in succinate dehydrogenase (SDH) that promotes carcinogenesis by the cytoplasmic accumulation of succinate. This rare group of GIST primarily occurs in the younger patients than other subtypes, and is frequently associated with hereditary syndromes. The role of TKIs in patients with SDH-deficient GIST is controversial, with conflicting results; thus, there is an urgent need to uncover the disease mechanisms, treatment patterns, and responses to systemic therapy among these patients. Here, based on an extensive literature search, we have provided a rigorous overview of the current evidence on the medical treatment of SDH-deficient GIST.