Genotyping and immunohistochemistry of gastrointestinal stromal tumors: An update

When Is It Important to Sequence Sarcomas and Other Mesenchymal Neoplasms? A Practical Guide to Molecular Testing

The increasingly widespread availability of next-generation sequencing has led to its incorporation as a diagnostic tool in pathology and a modality for identifying targetable alterations. However, sequencing is still a somewhat expensive and time-consuming. Here, we discuss tumor types for which (1) molecular testing is not generally indicated, (2) surrogate immunohistochemical markers have rendered molecular testing unnecessary, or (3) sequencing is important for diagnostic and therapeutic purposes. We also provide a practical framework to assist in decision-making for molecular testing of both classified and unclassified mesenchymal neoplasms, reflecting our practice in a tertiary sarcoma referral center.

Gastrointestinal stromal tumours (GIST) in children: An update of this orphan disease

BACKGROUND

Gastrointestinal stromal tumours (GIST) are tumours of the digestive tract that mainly develop in adults. Recommendations for the management of GIST in pediatrics are limited.

MATERIAL AND METHODS

We performed an updated review of the literature serving as a basis for the development of diagnostic and therapeutic recommendations for GIST in children and young adults (YA).

RESULTS

GIST in pediatric population can have a sporadic presentation but occur more often in a syndromic and/or familial context. Currently more than 170 cases of sporadic GIST or in association with Carney-Stratakis syndrome or Carney's triad family cases of familial GIST have been described in children and YA. These syndromes are frequently associated with germline or somatic alterations in a sub-unit of Succinate Dehydrogenase (SDH). In contrast, the frequency of somatic KIT and PDGFRα oncogene mutations (±15%) is significantly lower as compared to adults with GIST. The recommendations for the management of children with GIST are generally comparable to those used for adult patients, although certain biological differences influence the therapeutic attitude.

CONCLUSIONS

International collaborations have been deployed in order to increase the clinical and biological knowledge of this orphan pathology in pediatrics.

Pathologic diagnosis and molecular features of gastrointestinal stromal tumors: a mini-review

Gastrointestinal stromal tumors (GISTs) arise from the interstitial cells of Cajal, predominantly affecting the stomach and small intestine, with rare occurrences in the duodenum, rectum, and extraintestinal sites. Histologically, GISTs can present as spindle cells, epithelioid cells, or mixed morphologies, with immunohistochemical staining revealing expression of KIT (CD117) and discovered on GIST 1 (DOG1). Approximately 80% of GISTs harbor activating mutations in KIT or platelet derived growth factor receptor α (PDGFRA), which influence their clinical behavior and treatment response. SDH-deficient GISTs, associated with syndromes such as Carney triad and Carney-Stratakis syndrome, represent a distinct subgroup with unique characteristics and management challenges. The standard treatment includes surgery and imatinib for metastatic cases; however, resistance to tyrosine kinase inhibitors remains a significant hurdle, especially in pediatric and wildtype GISTs. This highlights the need for advanced therapeutic strategies and emphasizes the importance of molecular profiling in guiding treatment decisions and improving outcomes for GIST patients.

True Mitotic Count Prediction in Gastrointestinal Stromal Tumors: Bayesian Network Model and PROMETheus (Preoperative Mitosis Estimator Tool) Application Development

BACKGROUND

Gastrointestinal stromal tumors (GISTs) present a complex clinical landscape, where precise preoperative risk assessment plays a pivotal role in guiding therapeutic decisions. Conventional methods for evaluating mitotic count, such as biopsy-based assessments, encounter challenges stemming from tumor heterogeneity and sampling biases, thereby underscoring the urgent need for innovative approaches to enhance prognostic accuracy.

OBJECTIVE

The primary objective of this study was to develop a robust and reliable computational tool, PROMETheus (Preoperative Mitosis Estimator Tool), aimed at refining patient stratification through the precise estimation of mitotic count in GISTs.

METHODS

Using advanced Bayesian network methodologies, we constructed a directed acyclic graph (DAG) integrating pertinent clinicopathological variables essential for accurate mitotic count prediction on the surgical specimen. Key parameters identified and incorporated into the model encompassed tumor size, location, mitotic count from biopsy specimens, surface area evaluated during biopsy, and tumor response to therapy, when applicable. Rigorous testing procedures, including prior predictive simulations, validation utilizing synthetic data sets were employed. Finally, the model was trained on a comprehensive cohort of real-world GIST cases (n=80), drawn from the repository of the Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Humanitas Research Hospital, with a total of 160 cases analyzed.

RESULTS

Our computational model exhibited excellent diagnostic performance on synthetic data. Different model architecture were selected based on lower deviance and robust out-of-sample predictive capabilities. Posterior predictive checks (retrodiction) further corroborated the model's accuracy. Subsequently, PROMETheus was developed. This is an intuitive tool that dynamically computes predicted mitotic count and risk assessment on surgical specimens based on tumor-specific attributes, including size, location, surface area, and biopsy-derived mitotic count, using posterior probabilities derived from the model.

CONCLUSIONS

The deployment of PROMETheus represents a potential advancement in preoperative risk stratification for GISTs, offering clinicians a precise and reliable means to anticipate mitotic counts on surgical specimens and a solid base to stratify patients for clinical studies. By facilitating tailored therapeutic strategies, this innovative tool is poised to revolutionize clinical decision-making paradigms, ultimately translating into improved patient outcomes and enhanced prognostic precision in the management of GISTs.

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.

Biological and therapeutic implications of RKIP in Gastrointestinal Stromal Tumor (GIST): an integrated transcriptomic and proteomic analysis

BACKGROUND

Gastrointestinal stromal tumors (GIST) represent a significant clinical challenge due to their metastatic potential and limited treatment options. Raf kinase inhibitor protein (RKIP), a suppressor of the MAPK signaling pathway, is downregulated in various cancers and acts as a metastasis suppressor. Our previous studies demonstrated low RKIP expression in GIST and its association with poor outcomes. This study aimed to expand on the previous findings and investigate the biological and therapeutic implications of RKIP loss on GIST.

METHODS

To validate the RKIP prognostic significance, its expression was evaluated by immunohistochemistry in 142 bona fide GIST cases. The functional role of RKIP was evaluated in vitro, using the GIST-T1 cell line, which was knocked out for RKIP. The biological and therapeutic implications of RKIP were evaluated by invasion, migration, apoptosis, and 2D / 3D viability assays. Additionally, the transcriptome and proteome of RKIP knockout cells were determined by NanoString and mass spectrometry, respectively.

RESULTS

Immunohistochemical analysis revealed the absence of RKIP in 25.3% of GIST cases, correlating with a tendency toward poor prognosis. Functional assays demonstrated that RKIP knockout increased GIST cells' invasion and migration potential by nearly 60%. Moreover, we found that RKIP knockout cells exhibited reduced responsiveness to Imatinib treatment and higher cellular viability in 2D and 3D in vitro models, as assessed by apoptosis-related protein expression. Through comprehensive genetic and proteomic profiling of RKIP knockout cells, we identified several putative RKIP-regulated proteins in GIST, such as COL3A1.

CONCLUSIONS

Using a multidimensional integrative analysis, we identified, for the first time in GIST, molecules and pathways modulated by RKIP that may potentially drive metastasis and, consequently, poor prognosis in this disease.

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.

Mutational Profile and Pathological Features of a Case of Interleukin-10 and RGS1-Positive Spindle Cell Variant Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma with spindle cell morphology is a rare variant. We present the case of a 74-year-old male who initially presented with a right supraclavicular (lymph) node enlargement. Histological analysis showed a proliferation of spindle-shaped cells with narrow cytoplasms. An immunohistochemical panel was used to exclude other tumors, such as melanoma, carcinoma, and sarcoma. The lymphoma was characterized by a cell-of-origin subtype of germinal center B-cell-like (GCB) based on Hans’ classifier (CD10-negative, BCL6-positive, and MUM1-negative); EBER negativity, and the absence of BCL2, BCL6, and MYC rearrangements. Mutational profiling using a custom panel of 168 genes associated with aggressive B-cell lymphomas confirmed mutations in ACTB, ARID1B, DUSP2, DTX1, HLA-B, PTEN, and TNFRSF14. Based on the LymphGen 1.0 classification tool, this case had an ST2 subtype prediction. The immune microenvironment was characterized by moderate infiltration of M2-like tumor-associated macrophages (TMAs) with positivity of CD163, CSF1R, CD85A (LILRB3), and PD-L1; moderate PD-1 positive T cells, and low FOXP3 regulatory T lymphocytes (Tregs). Immunohistochemical expression of PTX3 and TNFRSF14 was absent. Interestingly, the lymphoma cells were positive for HLA-DP-DR, IL-10, and RGS1, which are markers associated with poor prognosis in DLBCL. The patient was treated with R-CHOP therapy, and achieved a metabolically complete response.

Radiological Evaluation of a Malignant Gastrointestinal Stromal Tumor in a Female Patient With the Coincidental Detection of Primary Breast Cancer: A Case Report

Gastrointestinal stromal tumors (GIST) are a rare and unique group of mesenchymal tumors arising from the gastrointestinal tract, omentum, mesentery, and retroperitoneum. Though they have certain typical radiological features that can differentiate them from epithelial tumors, it is often difficult to differentiate them from other non-epithelial tumors. Their features also vary depending on their size, site of origin, etc. When differentiation from other mesenchymal tumors on histopathology is difficult, receptor tyrosine kinase (C-KIT proto-oncogene/CD117) and gastrointestinal stromal tumor (GIST-1) discovered on GIST1 (DOG-1) expression are confirmatory. The concurrent presence of other primary cancers with GISTs has been described in the literature, among which most have been of gastrointestinal origin. Few cases of primary breast cancer in GIST have been described. Lymph nodal metastasis is rarely encountered in GIST, and metastasis to the breast is even rarer. We present a case of a 39-year-old female with non-specific symptoms who was referred for ultrasonography (USG) and computed tomography (CT) that showed a small intestinal GIST along with a breast lump and axillary lymphadenopathy that were labeled as metastases from the GIST on frozen sections; however, they were later diagnosed as primary breast cancer with axillary metastases on the histopathology and immunohistochemistry of the excision biopsy specimens post-surgery. The patient underwent surgical resection and chemotherapy.

Health-Related Quality of Life and Side Effects in Gastrointestinal Stromal Tumor (GIST) Patients Treated with Tyrosine Kinase Inhibitors: A Systematic Review of the Literature

BACKGROUND

The introduction of tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of gastrointestinal stromal tumors (GISTs), resulting in a substantial gain in median overall survival. Subsequently, health-related quality of life (HRQoL) has become more relevant. Here, we systematically review the available literature on HRQoL issues and side effects of different TKIs registered for the treatment of GIST.

METHODS

A search through five databases was performed. Full reports in English describing HRQoL outcomes and/or side effects in GIST patients on TKI therapy were included.

RESULTS

A total of 104 papers were included; 13 studies addressed HRQoL, and 96 studies investigated adverse events. HRQoL in patients treated with imatinib, regorafenib, and ripretinib remained stable, whereas most sunitinib-treated patients reported a decrease in HRQoL. Severe fatigue and fear of recurrence or progression were specifically assessed as HRQoL issues and had a negative impact on overall HRQoL as well as psychological and physical well-being. The majority of studies focused on physician-reported side effects. Nearly all GIST patients treated with a TKI experienced at least one adverse event, mostly mild to moderate.

CONCLUSIONS

Despite the fact that almost all patients treated with a TKI experienced side effects, this did not seem to affect overall HRQoL during TKI therapy. In daily practice, it are the side effects that hamper a patient's HRQoL resulting in treatment adjustments, suggesting that the reported side effects were underestimated by physicians, or the measures used to assess HRQoL do not capture all relevant issues that determine a GIST patient's HRQoL.

Recent Progress and Challenges in the Diagnosis and Treatment of Gastrointestinal Stromal Tumors

Simple Summary

Gastrointestinal stromal tumors (GIST) are potentially malignant tumors and require evidence-based surgical and/or medical treatment. Laparoscopy has similar safety and prognostic outcomes to those of laparotomy and is currently a standard procedure for localized GISTs. However, surgery for gastric GISTs less than 2 cm may be re-evaluated due to the indolent nature of the GIST and other competing risks among GIST patients. A work-up with endoscopy and endoscopic ultrasonography as well as endoscopic or percutaneous biopsy is important for the preoperative diagnosis of GISTs. Medical treatment with tyrosine kinase inhibitors is the mainstay for recurrent/metastatic GISTs. The activity of an individual drug is well correlated with gene alterations, and, in the era of precision medicine, cancer genome profiling should be considered before medical treatment.

Abstract

Gastrointestinal stromal tumors (GISTs) are the most frequent malignant mesenchymal tumors in the gastrointestinal tract. The clinical incidence of GISTs is estimated 10/million/year; however, the true incidence is complicated by frequent findings of tiny GISTs, of which the natural history is unknown. The initial work-up with endoscopy and endoscopic ultrasonography plays important roles in the differential diagnosis of GISTs. Surgery is the only modality for the permanent cure of localized GISTs. In terms of safety and prognostic outcomes, laparoscopy is similar to laparotomy for GIST treatment, including tumors larger than 5 cm. GIST progression is driven by mutations in KIT or PDGFRA or by other rare gene alterations, all of which are mutually exclusive. Tyrosine kinase inhibitors (TKIs) are the standard therapy for metastatic/recurrent GISTs. Molecular alterations are the most reliable biomarkers for TKIs and for other drugs, such as NTRK inhibitors. The pathological and genetic diagnosis prior to treatment has been challenging; however, a newly developed endoscopic device may be useful for diagnosis. In the era of precision medicine, cancer genome profiling by targeted gene panel analysis may enable potential targeted therapy even for GISTs without KIT or PDGFRA mutations.

Gastrointestinal Stromal Tumor in Monozygotic Twins Shows Distinct Mutational Status: A Case Report

Case series

Patients: Female, 62-year-old • Female, 62-year-old

Final Diagnosis: Gastrointestinal stromal tumor (GIST)

Symptoms: Abdominal pain • fatigue

Medication: —

Clinical Procedure: Genetic analysis

Specialty: Oncology

Progress in determining response to treatment in gastrointestinal stromal tumor

Introduction: Gastrointestinal stromal tumor (GIST) is the most common malignant mesenchymal tumor of the gastrointestinal system. Multiple advances in the management of GIST from the discovery of KIT/PDGRA and other genetic alterations have led to the development of multiple tyrosine kinase inhibitors. Response assessment in GIST is determined with iRECIST (Response Evaluation Criteria in Solid Tumors), PERCIST (PET response criteria in solid tumors), or Choi criteria. Molecular genotyping of the tissue samples is the recent standard for diagnosis, treatment, and response to treatment.Areas covered: In this study, we provide a brief overview of the history of the GIST, molecular sequencing, available treatment options and clinical trials, radiologic response assessment, and the role of ctDNA in response evaluation.Expert opinion: Future GIST management is related to the development of sensitive assays to detect genetic alterations for initial diagnosis, treatment selection, monitoring the response to treatment, resistant mutations, and predicting survival.

Frequency, localization, and types of gastrointestinal stromal tumor-associated neoplasia

BACKGROUND

In recent years, increasing evidence of second neoplasms associated with gastrointestinal stromal tumors (GIST) has been found. Numerous case reports, mostly retrospective studies and a few reviews, have been published. To our knowledge, however, no systematic review or meta-analysis of the existing data has been performed so far.

AIM

To prepare a compilation, as complete as possible, of all reported second tumor entities that have been described in association with GIST and to systematically analyze the published studies with regard to frequency, localization, and types of GIST-associated neoplasms.

METHODS

The MEDLINE and EBSCO databases were searched for a combination of the keywords GIST/secondary, synchronous, coincident/tumor, neoplasm, and relevant publications were selected by two independent authors.

RESULTS

Initially, 3042 publications were found. After deletion of duplicates, 1631 remained, and 130 papers were selected; 22 of these were original studies with a minimum of 20 patients, and 108 were case reports. In the 22 selected studies, comprising a total number of 12050 patients, an overall rate of GIST-associated neoplasias of 20% could be calculated. Most second neoplasias were found in the gastrointestinal tract (32%) and in the male and female urogenital tract (30%). The specific risk scores of GISTs associated with other tumors were significantly lower than those without associated neoplasias.

CONCLUSION

In this first systematic review, we could confirm previously reported findings of a more than coincidental association between GIST and other neoplasias. The question whether there is an underlying causal association will need further investigation. Our data suggest that even GIST with a very low risk of disease progression should prompt screening for second neoplasia and subsequent frequent controls or extended staging.

Clinicopathologic features and outcomes of gastrointestinal stromal tumors arising from the esophagus and gastroesophageal junction

Background

Our aim was to characterize the clinicopathological features and outcomes of gastrointestinal stromal tumors (GISTs) arising from the esophagus and gastroesophageal junction (GEJ) and describe the survival of patients treated at our institution as well as from a national hospital-based registry.

Methods

Twenty-eight cases were identified using the Mayo Clinic Cancer Registry from 1997 to 2016, and 1,010 cases from the National Cancer Database (NCDB) between 2004 and 2014, with analysis of TNM staging, histopathological features, mitotic index, immunohistochemical studies, and KIT mutational analysis.

Results

At Mayo Clinic, the tumors ranged in size from 0.3-13 cm (mean 5.40 cm). IHC results were: CD117 (KIT) in 100% (23/23 cases) and DOG1 in 100% (6/6), followed by CD34 (85.7%, 12/14), smooth muscle actin (27.8%, 5/18), desmin (18.2%, 2/11), and S-100 protein (13.3%, 2/15). Mutational analysis (performed in 10 cases) showed KIT exon 11 mutations in 8 cases; KIT mutation was not identified in 2 cases (presumed wild-type). Two-thirds of patients underwent surgery, of which 70% had an esophagectomy. Fourteen patients received adjuvant imatinib mesylate. Five patients had liver metastases at the time of diagnosis; none had lymph node metastases. A total of 38.9% of cases had recurrent or metastatic disease. Complete clinical follow-up was available for 10 patients (median follow-up duration 31.5 months; range, 10-145 months): one (male) had a local recurrence at the anastomotic site and one (female) suffered a liver metastasis; the others were either disease-free or had stable disease at the time of last follow-up. There was a significant association seen among metastatic disease and mitotic count >5/50 high-powered field (HPF) (P=0.016), with median mitotic rate 90/50 HPF (range, 7-500) for metastatic tumors versus 6/50 HPF (range, 0-100) for non-metastatic tumors. For metastatic disease, median tumor size was 7.3 cm (range, 1-66 cm) compared to 4.8 cm (range, 0.02-71 cm) for non-metastatic disease, which was also statistically significant (P≤0.0001). Two hundred and fifty-eight NCDB cases were risk stratified using the Joensuu criteria. Among 89 low risk category tumors, only 2 (2.2%) were ultimately metastatic. A total of 10.9% (15/138) of high risk category tumors were metastatic. The median overall survival (OS) from the time of diagnosis for the Mayo Clinic cohort was 129.5 months (95% CI, 55.7-not reached), with 5-year OS 85.7%. Median OS for the NCDB cohort was 135.95 months (95% CI, 104.08-not reached) with 5-year OS 68.2%. Superior OS was seen in females (HR 0.67, 95% CI, 0.49-0.89, P=0.006).

Conclusions

Among esophageal and GEJ GISTs, metastatic disease was associated with increased mitotic count and increased tumor size. Men were found to have inferior OS. The Joensuu risk criteria were validated for risk stratification of esophageal and GEJ GISTs.

Nationwide trends in the incidence and outcome of patients with gastrointestinal stromal tumour in the imatinib era

Background

The incidence, treatment and outcome of patients with newly diagnosed gastrointestinal stromal tumour (GIST) were studied in an era known for advances in diagnosis and treatment.

Methods

Nationwide population‐based data were retrieved from the Netherlands Cancer Registry. All patients with GIST diagnosed between 2001 and 2012 were included. Primary treatment, defined as any treatment within the first 6–9 months after diagnosis, was studied. Age‐standardized incidence was calculated according to the European standard population. Changes in incidence were evaluated by calculating the estimated annual percentage change (EAPC). Relative survival was used for survival calculations with follow‐up available to January 2017.

Results

A total of 1749 patients (54·0 per cent male and median age 66 years) were diagnosed with a GIST. The incidence of non‐metastatic GIST increased from 3·1 per million person‐years in 2001 to 7·0 per million person‐years in 2012; the EAPC was 7·1 (95 per cent c.i. 4·1 to 10·2) per cent (P < 0·001). The incidence of primary metastatic GIST was 1·3 per million person‐years, in both 2001 and 2012. The 5‐year relative survival rate increased from 71·0 per cent in 2001–2004 to 81·4 per cent in 2009–2012. Women had a better outcome than men. Overall, patients with primary metastatic GIST had a 5‐year relative survival rate of 48·2 (95 per cent c.i. 42·0 to 54·2) per cent compared with 88·8 (86·0 to 91·4) per cent in those with non‐metastatic GIST.

Conclusion

This population‐based nationwide study found an incidence of GIST in the Netherlands of approximately 8 per million person‐years. One in five patients presented with metastatic disease, but relative survival improved significantly over time for all patients with GIST in the imatinib era.

Surgery improves survival

The expression of MDM2 in gastrointestinal stromal tumors: immunohistochemical analysis of 35 cases

Background

Gastrointestinal stromal tumors (GIST) are the most common primary mesenchymal tumors of the digestive system. The assessment of their biological behavior still remains a scientific challenge. To date, there are no well-established biological prognostic markers of GIST. Our aim is to study the expression of the MDM2 oncoprotein in GIST through an immunohistochemical analysis.

Methods

It was a retrospective study of 35 cases of GIST diagnosed from 2009 to 2012 in the department of pathology of Hassan II university hospital, Fès, Morocco. MDM2 immunohistochemical staining was performed on archival paraffin-embedded and formalin-fixed specimens (with a threshold of nuclear positivity > 10%). Analysis of correlations between MDM2 immunoexpression and clinicopathological features of GIST has been performed.

Results

The mean age was 55.23 years (range 25–84 years) with a male predominance (sex ratio = 1.5). The stomach was the main site of GIST, with 17 cases (48.57%) followed by the small bowel (9 cases, 25.71%). The spindle cell type GIST was the most frequent morphological variant (29 cases, 82.85%). Tumor necrosis was present in 8 cases (22.85%). Two patients (5.71%) had very low risk GIST, 5 (14.28%) had low risk GIST, 7 patients (20%) had intermediate risk tumors. The remaining 21 cases (60%) had high risk GIST. At the time of diagnosis, 9 patients (25.71%) had metastatic tumors. At immunohistochemical analysis, 40% of cases (14 patients) stained positive for MDM2. Of these MDMD2-positive tumors, 11/14 (78.57%) had high risk tumors and 8/14 cases (57.14%) presented with metastatic GIST. MDM2 positivity was significantly associated with the metastatic status (p = 0.001).

Conclusion

The current study suggests that MDM2 immunohistochemical expression is a negative histoprognostic factor in GIST with a statistically significant correlation with metastasis.

Gastrointestinal stromal tumor of unusual phenotype after imatinib treatment: A case report and diagnostic utility of ETV1 mRNA in situ hybridization

RATIONALE

Gastrointestinal stromal tumor (GIST) is the most common tumor of mesenchymal origin in gastrointestinal tract. Immunohistochemical (IHC) staining combined with a typical morphology is used for the diagnosis of GIST. Typically, IHC staining for v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene (KIT) and discovered on GIST-1(DOG1) is positive in almost all GISTs. However, imatinib mesylate, a specific inhibitor of KIT tyrosine kinase, frequently involves changes in the morphology and IHC staining of GIST, impeding the diagnosis. Recently, in situ hybridization (ISH) for E26 transformation-specific sequence variant 1 (ETV1) mRNA was introduced as a useful marker to diagnose GIST.

PATIENT CONCERNS

We report 2 cases of gastric GIST, which expressed unusual phenotypes after imatinib therapy.

DIAGNOSES

The first patient was found to have a gastric subepithelial tumor in gastroduodenoscopy done for regular checkup. In biopsy of the tumor, it showed homogenous spindle cells that were positive to standard IHC markers for GIST. The second patient visited our hospital because of a palpable mass in the abdomen. In abdominal computed tomography (CT), a tumor arising from the stomach was found. A needle biopsy was done and the patient was diagnosed of gastric GIST because the biopsy showed spindle cells positive to typical IHC markers for GIST. After imatinib treatment, in both patients, the resected tumors were composed of heterogeneous spindle cells negative to KIT, DOG1, and CD34 IHC staining, which was unusual for GIST. However, ISH for ETV1 mRNA done for both biopsied and resected tumors was positive, even after imatinib treatment. A molecular analysis found a mutation in exon 11 of KIT gene before and after imatinib therapy in both patients, confirming the diagnosis of GIST.

INTERVENTIONS

Both patients took neoadjuvant imatinib treatment, and afterwards, underwent a surgical resection.

OUTCOMES

The patients remain on imatinib treatment and no progression or recurrence has been detected to date.

LESSONS

ISH for ETV1 mRNA is a useful technique in diagnosing GIST when IHC with KIT, DOG1, or CD34 fail to stain positive after imatinib therapy.

Lack of microsatellite instability in gastrointestinal stromal tumors

The microsatellite instability (MSI) phenotype may constitute an important biomarker for patient response to immunotherapy, particularly to anti-programmed death-1 inhibitors. MSI is a type of genomic instability caused by a defect in DNA mismatch repair (MMR) proteins, which is present mainly in colorectal cancer and its hereditary form, hereditary nonpolyposis colorectal cancer. Gastrointestinal stromal tumor (GIST) development is associated with activating mutations of KIT proto-oncogene receptor tyrosine kinase (KIT) or platelet-derived growth factor receptor α (PDGFRA), which are oncogenes that predict the response to imatinib mesylate. In addition to KIT/PDGFRA mutations, other molecular alterations are important in GIST development. In GISTs, the characterization of the MSI phenotype is scarce and the results are not consensual. The present study aimed to assess MSI in a series of 79 GISTs. The evaluation of MSI was performed by pentaplex polymerase chain reaction comprising five markers, followed by capillary electrophoresis. The expression of MMR proteins was evaluated by immunohistochemistry. Regarding the KIT/PDGFRA/B-Raf proto-oncogene, serine/threonine kinase molecular profile of the 79 GISTs, 83.6% of the tumors possessed KIT mutations, 10.1% had PDGFRA mutations and 6.3% were triple wild-type. The mutated-PDGFRA cases were associated with gastric location and a lower mitotic index compared with KIT-mutated and wild-types, and these patients were more likely to be alive and without cancer. MSI analysis identified 4 cases with instability in one marker, however, additional evaluation of normal tissue and immunohistochemical staining of MMR proteins confirmed their microsatellite-stable nature. The results of the present study indicated that MSI is not involved in GIST tumorigenesis and, therefore, cannot serve as a biomarker to immunotherapy response in GIST.

PDGFRA and KIT Mutation Status and Its Association With Clinicopathological Properties, Including DOG1

Most of the gastrointestinal stromal tumors (GISTs) have gain-of-function mutations in the KIT gene, which can be used as a prognostic marker for the biological behavior of tumors, predictive marker for the response of tyrosine kinase inhibitors, and diagnostic marker. Researchers have focused on PDGFRA mutations because of both their prognostic and predictive potential and DOG1 positivity for diagnosis on GISTs. The aim of this study is to investigate the effect DOG1, PDGFRA, and KIT mutations on the prediction of the outcome for GIST management. Polymerase chain reaction was performed for KIT gene exons 9, 11, 13, and 17 and PDGFRA gene exons 12 and 18 with the genomic DNA of 46 GIST patients, and amplicons were sequenced in both directions. Immunocytochemical stainings were done by using primary antibodies. Molecular analysis revealed that the KIT mutation was observed in 63% of all cases, while the PDGFRA mutation was observed in 23.9% of cases. Significant relationships were found between age and KIT mutation, tumor location and KIT mutations, and tumor location and PDGFRA mutations (p ≤ 0.05). DOG1 positivity was detected in 65.2% of all GISTs and DOG1-positive cells had a higher KIT mutation ratio than DOG1-negative cells (p ≤ 0.05). KIT gene exon 11 mutations in DOG1-positive cells was higher than DOG1-negative cells (p ≤ 0.05). Conversely, KIT gene exon 13 mutations were higher in DOG1-negative cells than DOG1-positive cells (p ≤ 0.05). In this study, KIT mutation frequency was found similar with the European population; conversely, PDGFRA mutation frequency was similar with an Asian-Chinese-based study. KIT/PDGFRA mutations and tumor location can be used for the prediction of tumor behavior and the management of disease in GISTs. DOG1 positivity might be a candidate marker to support KIT and PDGFRA mutations, due to the higher DOG1 positivity in KIT exon 11 mutant and stomach- and small intestine-localized GISTs.

Molecular cytology genotyping of primary and metastatic GI stromal tumors by using a custom two-gene targeted next-generation sequencing panel with therapeutic intent

BACKGROUND AND AIMS

In an era of precision medicine, customized genotyping of GI stromal tumors by screening for driver mutations will become the standard of care. The fidelity of genotype concordance between paired cytology smears and surgical pathology specimens is unknown. In patients with either primary or metastatic sporadic disease, we sought to determine the frequency of KIT and PDGFRA pathogenic alterations within such specimens, imatinib sensitivity, and the concordance of pathogenic alterations between paired specimens.

METHODS

DNA obtained from cytology smears from 36 patients, 24 of whom had paired surgical pathology specimens, underwent targeted next-generation sequencing by using a custom panel to evaluate somatic mutations within KIT (exon 2, 9, 10, 11, 13, 14, 15, 17, 18) and PDGFRA (exon 12, 14, 15, 18) genes. Patients with KIT and PDGRFA wild-type genes completed the Qiagen Human Comprehensive Cancer GeneRead DNAseq Targeted Array V2.

RESULTS

Genotyping revealed KIT and PDGFRA mutations in 68% and 15% of patients. The wild-type population did not harbor mutations in BRAF, RAS family, SDHB, SETD2, or NF1. Imatinib sensitivity based on the oncogenic kinase mutation prevalence was estimated to be 68%. Mutational concordance between paired cytology and surgical pathology specimens was 96%.

CONCLUSIONS

Our data have demonstrated the ability to stratify either primary or metastatic gastrointestinal stromal tumors by mutational subtype using a targeted next-generation sequencing 2 gene mutation panel. We highlight the ability to use cytology specimens obtained via minimally invasive techniques as a surrogate to surgical specimens given the high mutational landscape concordance between paired specimens.

Molecular and Immunohistochemical Study of Platelet Derived Growth Factor Receptor Alpha in KIT Negative Gastrointestinal Stromal Tumors; the First Report from Iran

BACKGROUND Gastrointestinal stromal tumors (GISTs) are potentially malignant tumors; however their behavior and response to treatment is dependent on the type of mutation and immunohistochemical expression of antigens. It is recommended to perform routine molecular and immunohistochemical tests in KIT and platelet derived growth factor receptor alpha (PDGFRA) molecules for making decision regarding targeted therapy and prediction of the behavior of the tumor.

OBJECTIVES

There has been no study from Iran regarding the PDGFRA mutational analysis in GISTs. In this study, for the first time from Iran, we performed immunohistochemical and molecular analysis of PDGFRA molecule on GISTs. METHODS In a cross-sectional study during 7 years (2008-2014) on 50 untreated non-recurrent non-metastatic newly diagnosed GISTs, molecular analysis and immunohistochemical staining for PDGFRA were performed and findings were compared with different clinicopathological characteristics.. RESULTS During the 7 years, 50 cases of GISTs according to the above mentioned criteria were found. 17 cases were negative for KIT mutation. Of them, 15 (30%) were positive for either exon 12 or 18 mutation of PDGFRA. These cases showed more epithelioid morphology and the number of mitotic figures were lower than PDFRA negative GISTs. Also according to the criteria for risk assessment, it seems that PDGFRA mutant GISTs are rarely in the high risk category. CONCLUSION PDGFRA mutant GISTs are common in Iranian population and it is recommended to perform mutation analysis for PDGFRA in every GIST with wild type KIT and epithelioid morphology.

Metastatic Gastrointestinal Stromal Tumor to the Skull

BACKGROUND

Gastrointestinal stromal tumors (GISTs) arising from the interstitial cells of Cajal along the gastrointestinal tract rarely metastasize to the central nervous system (CNS) but require aggressive multimodal therapies when they do. We present a case of recurrent GIST metastasis to the skull and review the literature on management, including the role of molecular profiling in determining adjuvant treatment.

CASE

A 64-year-old woman presented with an enlarging palpable mass over her right eye. Magnetic resonance imaging revealed an enhancing T1-hypointense, T2-hyperintense right frontal calvarial lesion with lytic features on computed tomography. Pathology confirmed metastatic GIST to the skull with dural involvement. Molecular profiling revealed a mutation in exon 11 of KIT in her primary tumor, while the skull metastasis harbored an additional mutation in exon 17 associated with acquired drug resistance.

CONCLUSION

We review the epidemiology of GIST metastases and discuss potential reasons for its rare presentation to the CNS. Additionally, we highlight the diagnostic and prognostic value of molecular profiling for metastatic GIST, as well as its influence in arbitrating targeted molecular inhibitor therapy. Evolving molecular signatures, associated with treatment resistance, may play a pivotal role in future integration with multimodality treatment strategies for CNS GIST.

SDHC methylation in gastrointestinal stromal tumors (GIST): a case report

BACKGROUND

Gastrointestinal stromal tumors (GIST) recently have been recognized as a genetically and biologically heterogeneous disease. In addition to KIT or PDGFRA mutated GIST, mutational inactivation of succinate dehydrogenase (SDH) subunits has been detected in the KIT/PDGFRA wild-type subgroup, referred to as SDH deficient (dSDH). Even though most dSDH GIST harbor mutations in SDHx subunit genes, some are SDHx wild type. Epigenetic regulation by DNA methylation of CpG islands recently has been found to be an alternative mechanism underlying the lack of SDH complex in GIST.

CASE PRESENTATION

We report a particular case of dSDH GIST, previously analyzed with microarrays and next-generation sequencing, for which no molecular pathogenetic events have been identified. Gene expression analysis showed remarkable down-modulation of SDHC mRNA with respect to all other GIST samples, both SDHA-mutant and KIT/PDGFRA-mutant GIST. By a bisulfite methylation assay targeted to 2 SDHC CpG islands, we detected hypermethylation of the SDHC promoter.

CONCLUSION

Herein we report an additional case of dSDH GIST without SDHx mutation but harboring hypermethylation in the SDHC promoter, thus confirming the complexity of the molecular background of this subtype of GIST.

DOG1 Expression in Low-Grade Fibromyxoid Sarcoma

DOG1 is a highly sensitive marker for gastrointestinal stromal tumor (GIST) and is in the routine diagnostic antibody repertoire of many surgical pathology laboratories. Moreover, GIST is well recognized by both pathologists and clinicians in the differential diagnosis of intra-abdominal and pelvic neoplasms. Low-grade fibromyxoid sarcoma (LGFMS) is, however, much less frequently anticipated, particularly when occurring at unusual sites, because of its rarity and bland histology, particularly on core biopsy. We describe a case of a 53-year-old male with a large pelvic and pararectal mass, which on biopsy showed a moderately cellular spindle cell neoplasm within fibrous stroma. Immunohistochemistry at the referring center showed diffuse and strong expression of DOG1 with negativity for other markers. After referral to a tertiary center, repeat DOG1 immunohistochemistry again showed diffuse expression, but MUC4 was also positive, and this was confirmed to be LGFMS, harboring FUS-CREB3L2 fusion transcripts by reverse transcription-polymerase chain reaction and FUS rearrangement with fluorescence in situ hybridization. In view of this we assessed DOG1 expression in 10 other LGFMS (all MUC4 positive, and 9 molecularly confirmed to harbor FUS-CREB3L2 fusion transcripts and/or FUS or EWSR1 gene rearrangement), of which 5 showed DOG1 expression in up to 75% of tumor cells, varying in intensity from weak to strong. While LGFMS and GIST are generally morphologically dissimilar, less typical variants of each exist, and both can contain bland spindled cells within fibrous stroma. As the morphologic spectrum of LGFMS is wide, and as it can occur in unusual sites and may not be well recognized by general pathologists and non–soft tissue pathologists, we highlight the potential for diagnostic confusion with GIST owing to aberrant DOG1 expression. This is clinically pertinent, as the management and prognosis of these 2 neoplasms differs significantly.

Rare Neoplasia of the Stomach

BACKGROUND

Gastric adenocarcinoma accounts for more than 90% of malignant lesions of the stomach. Besides this entity, numerous neoplastic lesions with malignant or benign characteristics as well as lesions with uncertain malignant potential occur. This review gives an overview on rare neoplasia of the stomach, focusing on gastric polyps, gastrointestinal stromal tumors, gastric lymphoma and neuroendocrine neoplasia.

SUMMARY

A broad spectrum of rare neoplastic lesions of the stomach with significant differences in malignant potential and with specific demands of interventional therapy is known. In addition to the use of high-definition endoscopy techniques, the histopathological assessment of lesions and of the surrounding mucosa is mandatory to characterize and differentiate malignant and benign tumors.

KEY MESSAGE

Rare neoplasia of the stomach is detected in approximately 6% of patients undergoing esophagogastroduodenoscopy. Diligent examination of the gastric mucosa remains essential to detect mucosal and submucosal lesions.

PRACTICAL IMPLICATIONS

Presenting with a broad spectrum of symptoms, ranging from unspecific abdominal discomfort to gastrointestinal bleeding or symptoms of gastric outlet obstruction, different rare neoplastic lesions of the stomach with demand of specific diagnostic and therapeutic work-up occur. Diligent endoscopic evaluation of the entire gastric mucosa, preferably by high-definition endoscopy techniques, is essential in addition to histopathological examination of lesional and surrounding tissue.