A Predictor Combining Clinical and Genetic Factors for AML1-ETO Leukemia Patients

Core Binding Factor (CBF)-AML is one of the most common somatic mutations in acute myeloid leukemia (AML). t(8;21)/AML1-ETO-positive acute myeloid leukemia accounts for 5-10% of all AMLs. In this study, we consecutively included 254 AML1-ETO patients diagnosed and treated at our institute from December 2009 to March 2020, and evaluated molecular mutations by 185-gene NGS platform to explore genetic co-occurrences with clinical outcomes. Our results showed that high KIT VAF(≥15%) correlated with shortened overall survival compared to other cases with no KIT mutation (3-year OS rate 26.6% vs 59.0% vs 69.6%, HR 1.50, 95%CI 0.78-2.89, P=0.0005). However, no difference was found in patients’ OS whether they have KIT mutation in two or three sites. Additionally, we constructed a risk model by combining clinical and molecular factors; this model was validated in other independent cohorts. In summary, our study showed that c-kit other than any other mutations would influence the OS in AML1-ETO patients. A proposed predictor combining both clinical and genetic factors is applicable to prognostic prediction in AML1-ETO patients.

PDGRFA-mutant gastrointestinal stromal tumours (GISTs) in Eastern England: clinicopathological features and outcomes of 50 patients diagnosed between 2008-2021

Background PDGRFA-mutant gastrointestinal tumours (GISTs) comprise approximately 10% of GISTs and are mostly gastric. Targeted therapies against these tumours have historically been limited by tyrosine kinase inhibitor (TKI)-resistance. We reviewed the characteristics and outcome of all PDGRFA-mutant patients seen at our centre over the last 13 years. Methods All PDGRFA-mutant patients seen at the Cambridge University Hospitals NHS Foundation Trust GIST clinic from July 2008-July 2021 were retrospectively reviewed and followed up. Results: 50 PDGRFA-mutant GIST patients were diagnosed during the 13-year period. 60% were male. Median tumour size was 5 cm and the majority were epithelioid (44%) or mixed (36%) type. Commonest primary location was the gastric body (52%). In non-metastatic patients the low-risk modified AFIP risk group was the most common (65.2%). PDGFRA exon 18 (86%) were the most common PDGFRA mutations, most being imatinib resistant. None harboured a KIT mutation. 38% of cases had high KIT expression (immunohistochemistry), whilst 48% had patchy expression and 14% were negative. Most were positive for DOG1 (94%). CD34 was highly expressed in 48% of cases. 13% developed metastases during the 13-year follow-up period: liver (80%) being the commonest site. 76% of all patients underwent radical resection. 14% received TKI therapy. After a median follow-up of 55.1 months, 82% remained alive: 6 patients died from metastatic GIST; 3 from other causes. Median time to metastatic disease was 30.1 months, and median time from metastatic diagnosis to death was 18.5 months. Patients who presented with metastatic disease had the poorest survival outcome (p=0.001) Conclusion To date this is the largest single-centre European PDGRFA-mutant GIST cohort. Results highlight the generally indolent nature of PDGRFA-mutant disease (contrasted to the poor outcome of those who present with metastatic disease), male and gastric preponderance (unlike KIT-mutant GISTs), and variable KIT expression.

Myeloproliferative Hypereosinophilic Syndrome with Concomitant Ischemic Events

Background: Eosinophils are versatile reactionary cells that play a key role in the inflammatory response. Excessive proliferation and aggregation of eosinophils have been implicated in the pathogenesis of ischemic neurologic and cardiac events. We present a rare case of hypereosinophilic syndrome (HES) in a patient hospitalized for simultaneous acute cerebrovascular accident (CVA) and acute coronary syndrome. Case: A 53-year-old male with past medical history of hypertension and diabetes mellitus presented with new onset bifrontal headache, right arm numbness and apraxia, and concurrent typical angina. On physical examination, he had small non-tender raised nodules on the bilateral upper and lower limbs. MRI of the brain demonstrated multifocal infarcts in a watershed distribution. Biochemical investigation revealed rising troponins. Splenomegaly of 16.4 cm was found on CT imaging. He was admitted for management of acute CVA and non-ST segment elevation myocardial infarction (NSTEMI). Complete blood count (CBC) revealed leukocytosis (34.4 K/mcL) with an eosinophilia of 85% and an absolute eosinophil count (AEC) of 29.2 x 10 3 eosinophils/µL. Serum tryptase was 29.2 µg/L. The patient was started on a high dose steroid with subsequent resolution of his neurologic and cardiac symptoms. Due to high suspicion for HES, FISH panel and bone marrow biopsy were performed. A small focus of marrow on his biopsy showed abundant eosinophils and bland spindle cells (>15 mast cells in aggregate). FISH panel was positive for 4q12 rearrangement, consistent with a FIP1L1/PDGFRA fusion mutation. Skin biopsy of his lesions demonstrated superficial and deep inflammation with eosinophils. He was diagnosed with myeloproliferative HES with features of mastocytosis and started on imatinib. Discussion: The defining features of HES consist of eosinophilia greater than 1500/µL for greater than 6 months with evidence of eosinophil induced tissue infiltration and injury. The ability of eosinophils to induce pathologic outcomes is influenced by a variety of parameters, including the number of eosinophils present, their location, and the degree of activation. Published data suggests that neurologic and cardiac ischemic events occur in HES patients with a higher leukocyte count and AEC than what we present with in this case. Our patient meets the main lab criteria of HES and our case highlights that simultaneous clinical manifestations can occur in the absence of markedly elevated peripheral eosinophilia. As with most cases involving unexplained hypereosinophilia, a wide range of diagnostic testing was necessary. The presence of a PDGFRA fusion mutation established a clonal disorder, supporting the diagnosis of myeloproliferative HES variant. The presence of eosinophils and the lack of mast cells on skin biopsy further supports myeloproliferative HES variant rather than a true systemic mastocytosis. Despite recent advances in molecular and immunologic therapies, treatment for HES remains challenging due to the wide variety of etiological classifications necessitating targeted treatments. At the time of submission, KIT mutation analysis is pending. Identification of a KIT D816V mutation would support use of midostaurin or the recently approved avapritinib for treatment of overlap syndrome. Disclosures No relevant conflicts of interest to declare.

Indolent systemic mastocytosis or just ‘atypical enterocolic mast cell aggregates’?

Introduction/Objective Mastocytosis is a rare disease in which there are abnormal mast cell accumulation in one or more tissue sites. Multifocal dense mast cell aggregates with atypical morphology or immunohistochemistry are considered as systemic mastocytosis (SM) based on WHO criteria. SM usually involves bone marrow and majority of them also have KIT mutation. There are rare case reports of atypical enterocolic mast cell aggregates (EMCA) confined to gastrointestinal (GI) only with mild or no symptoms. Here we present a case with extensive atypical mast cell aggregates in lower GI tract yet no evidence of involvement of other organs. Methods/Case Report A 34-year-old woman presented with abdominal bloating, diarrhea along with pruritis but no cutaneous lesion. Biopsies from the ascending and descending colons, caecum and rectum consistently showed increased eosinophils and multifocal infiltrates of atypical spindle shaped mast cells which are positive for CD117/tryptase but negative for CD2 and CD25. This is consistent with SM by WHO criteria based on morphology. Bone marrow biopsy showed normal amount of mast cells with normal morphology. Upper gastrointestinal biopsy was unremarkable. Serum tryptase level was normal. No KIT mutation was detected in exon 9, 11, 13 or 17 from colonic mucosa. Patient has been treated with antihistamine and Montelukast and symptoms resolved. Results (if a Case Study enter NA) N/A Conclusion This case met the criteria of SM based on the presence of multifocal mast cell aggregates and atypical spindle morphology >25%. Johncilla et al. previously reported 16 cases of EMCA with atypical morphology or immunohistochemistry, absent to mild localized symptoms, and negative KIT mutation. Based on lack of generalized disease, the authors preferred using descriptive terminology instead of ‘systemic mastocytosis’ for those cases. Our case has broader involvement of lower gastrointestinal tract than any reported case and the patient needs treatment for the symptoms. However, there is no ‘systemic’ involvement of bone marrow or any other organ. The diagnosis of ‘Systemic Mastocytosis’ would cause potential confusion and/or unnecessary anxiety. Further study of more cases is needed to better characterize and categorize the cases of atypical mast cell aggregates localized only to the GI.

Aggressive Behavior of Gastrointestinal Stromal Tumors (GISTs) Involving the Female Genital Tract (GYN- GIST) is Associated with TP53 Alterations

Introduction/Objective Women with female reproductive system involvement by GISTs have an unfavorable outcome. We explored the possibility that the more aggressive behavior of GYN-GIST is related to a specific genetic alteration. Our objective was to study such tumors in a cohort of women in search of actionable genes for evolving targeted therapy. Methods/Case Report The pathology databases (2004-2020) of the participating institutions were searched for GIST with histologically proven GYN-GIST (study group). The control group consisted of women known to have high risk GIST without genital tract involvement. Patients for whom genetic testing of their GISTs and follow-up information were available were included in the study. Results (if a Case Study enter NA) Of 1082 patients with GIST, eight patients fulfilled the study group criteria. Primary sites for both groups were as follows: 5 small bowel, 1 colon, 1 rectum, 1 stomach. The mean follow-up period was 86 and 77 months (study and control, respectively, p=0.34). Favorable outcomes (disease free, stable disease) were seen in 2 and 5 women (study and Control, respectively). Unfavorable outcomes (death, progression on treatment) were seen in 6 and 3 women (study and control, respectively, p<0.05). All patients had initial KIT mutation (exons 11 or 9). In addition, 4 patients from the study group (of 5 tested) had alteration in TP53. One patient without TP53 alterations is disease free. None of the neoplasms from 8 patients tested in the control group had TP53 alterations; fatal outcomes in this group were related to superimposed KIT exon 17 mutation. Conclusion Alterations in TP53 (linked to the poor outcome in a host of tumors) may be related to adverse outcome in patients GYN-GIST patients and may be a potential focus as targeted therapy evolves in those patients.

Sustained response to imatinib in patient with extraskeletal myxoid chondrosarcoma and novel KIT mutation

A 55-year-old woman presented with a 3-month history of right groin swelling, discomfort and impaired mobility. On examination, a palpable mass was noted both to the right of midline in the lower abdomen and in the right groin. MRI of the pelvis showed two masses involving the anterior abdominal wall and right groin, as well as lymph node involvement. CT imaging revealed multiple bilateral pulmonary metastases. Pathology demonstrated a myxohayline stroma morphology. Tumour was also notable for NR4A3 gene region rearrangement and mutation in KIT exon 11 at position c.1669 T>G. Based on these findings, she was diagnosed with extraskeletal myxoid chondrosarcoma (EMC). The patient has been on imatinib, a tyrosine kinase inhibitor with activity against KIT, for 3 years with stable disease. Metastatic EMC is generally treated with surgical resection and perioperative radiation therapy with adjuvant chemotherapy and is associated with poor prognosis.

Combined Inhibition of AKT and KIT Restores Expression of Programmed Cell Death 4 (PDCD4) in Gastrointestinal Stromal Tumor

The majority of gastrointestinal stromal tumor (GIST) patients develop resistance to the first-line KIT inhibitor, imatinib mesylate (IM), through acquisition of secondary mutations in KIT or bypass signaling pathway activation. In addition to KIT, AKT is a relevant target for inhibition, since the PI3K/AKT pathway is crucial for IM-resistant GIST survival. We evaluated the activity of a novel pan-AKT inhibitor, MK-4440 (formerly ARQ 751), as monotherapy and in combination with IM in GIST cell lines and preclinical models with varying IM sensitivities. Dual inhibition of KIT and AKT demonstrated synergistic effects in IM-sensitive and -resistant GIST cell lines. Proteomic analyses revealed upregulation of the tumor suppressor, PDCD4, in combination treated cells. Enhanced PDCD4 expression correlated to increased cell death. In vivo studies revealed superior efficacy of MK-4440/IM combination in an IM-sensitive preclinical model of GIST compared with either single agent. The combination demonstrated limited efficacy in two IM-resistant models, including a GIST patient-derived xenograft model possessing an exon 9 KIT mutation. These studies provide strong rationale for further use of AKT inhibition in combination with IM in primary GIST; however, alternative agents will need to be tested in combination with AKT inhibition in the resistant setting.