Clinical utility of whole-genome DNA methylation profiling as a primary molecular diagnostic assay for central nervous system tumors-A prospective study and guidelines for clinical testing.

Background: Central nervous system (CNS) cancer is the 10th leading cause of cancer-associated deaths for adults, but the leading cause in pediatric patients and young adults. The variety and complexity of histologic subtypes can lead to diagnostic errors. DNA methylation is an epigenetic modification that provides a tumor type-specific signature that can be used for diagnosis. Methods: We performed a prospective study using DNA methylation analysis as a primary diagnostic method for 1921 brain tumors. All tumors received a pathology diagnosis and profiling by whole genome DNA methylation, followed by next-generation DNA and RNA sequencing. Results were stratified by concordance between DNA methylation and histopathology, establishing diagnostic utility. Results: Of the 1602 cases with a World Health Organization histologic diagnosis, DNA methylation identified a diagnostic mismatch in 225 cases (14%), 78 cases (5%) did not classify with any class, and in an additional 110 (7%) cases DNA methylation confirmed the diagnosis and provided prognostic information. Of 319 cases carrying 195 different descriptive histologic diagnoses, DNA methylation provided a definitive diagnosis in 273 (86%) cases, separated them into 55 methylation classes, and changed the grading in 58 (18%) cases. Conclusions: DNA methylation analysis is a robust method to diagnose primary CNS tumors, improving diagnostic accuracy, decreasing diagnostic errors and inconclusive diagnoses, and providing prognostic subclassification. This study provides a framework for inclusion of DNA methylation profiling as a primary molecular diagnostic test into professional guidelines for CNS tumors. The benefits include increased diagnostic accuracy, improved patient management, and refinements in clinical trial design.

Leiomyoma-like Morphology in Metastatic Uterine Inflammatory Myofibroblastic Tumors.

Uterine inflammatory myofibroblastic tumors (IMTs) are rare mesenchymal neoplasms that frequently harbor ALK gene rearrangements and have a low risk of metastasis. We reported 3 of these tumors mimicking the appearance of leiomyoma in their recurrence. These patients were 34, 43, and 45 years old. Two uterine tumors demonstrated classic morphology, with combined myxoid, compact fascicular, and hyalinized patterns and spindled cells with bipolar cytoplasmic processes, moderate atypia, and lymphoplasmacytic inflammatory infiltrates. The third had a "leiomyoma-like" appearance, with fascicles of plump spindled cells and a sparse lymphoplasmacytic infiltrate. ALK immunohistochemistry was positive in all the tumors, and all demonstrated ALK rearrangements using fluorescence in situ hybridization (n = 2) and/or RNA sequencing (n = 2). Two classic IMTs recurred at 3 and 50 months in the lung and abdomen, respectively, and recurrent tumors had a "leiomyoma-like" appearance, with 0 and 1 mitosis per 10 high-power fields, no inflammation in 1, and a sparse lymphocytic infiltrate in the other. ALK was positive in both tumors; 1 with available tissue showed an IGFBP5::ALK fusion using RNA sequencing. The third patient, who had a "leiomyoma-like" uterine tumor, experienced multiple recurrences, first in the abdomen at 100 months showing a similar appearance. Subsequent recurrence at 105 months showed transmural invasion of the sigmoid colon and a similar microscopic appearance but with the addition of infiltrative borders, moderate cellularity, mild-to-moderate atypia, and 10 mitoses per 10 high-power fields. Both recurrences were positive for ALK, and RNA sequencing revealed the same ACTG2::ALK fusion transcript identified in the primary tumor. The patient was treated with crizotinib, resulting in prolonged clinical remission, with no evidence of disease at 168 months from the initial surgery. Although "leiomyoma-like" uterine IMTs have been recently described, to our knowledge, this is the first report of recurrence of these tumors and the first report of a "leiomyoma-like" appearance in the recurrences of conventional uterine IMTs. A low threshold for performing ALK immunohistochemistry on recurrent uterine tumors can identify patients who may benefit from tyrosine kinase inhibitors.

Single-cell sequencing reveals suppressive transcriptional programs regulated by MIS/AMH in neonatal ovaries.

Müllerian inhibiting substance (MIS/AMH), produced by granulosa cells of growing follicles, is an important regulator of folliculogenesis and follicle development. Treatment with exogenous MIS in mice suppresses follicle development and prevents ovulation. To investigate the mechanisms by which MIS inhibits follicle development, we performed single-cell RNA sequencing of whole neonatal ovaries treated with MIS at birth and analyzed at postnatal day 6, coinciding with the first wave of follicle growth. We identified distinct transcriptional signatures associated with MIS responses in the ovarian cell types. MIS treatment inhibited proliferation in granulosa, surface epithelial, and stromal cell types of the ovary and elicited a unique signature of quiescence in granulosa cells. In addition to decreasing the number of growing preantral follicles, we found that MIS treatment uncoupled the maturation of germ cells and granulosa cells. In conclusion, MIS suppressed neonatal follicle development by inhibiting proliferation, imposing a quiescent cell state, and preventing granulosa cell differentiation.

Histiocytic and Dendritic Cell Sarcomas of Hematopoietic Origin Share Targetable Genomic Alterations Distinct from Follicular Dendritic Cell Sarcoma.

BACKGROUND: Histiocytic and dendritic cell neoplasms are a diverse group of tumors arising from monocytic or dendritic cell lineage. Whereas the genomic features for Langerhans cell histiocytosis and Erdheim-Chester disease have been well described, other less common and often aggressive tumors in this broad category remain poorly characterized, and comparison studies across the World Health Organization diagnostic categories are lacking. METHODS: Tumor samples from a total of 102 patient cases within four major subtypes of malignant histiocytic and dendritic cell neoplasms, including 44 follicular dendritic cell sarcomas (FDCSs), 41 histiocytic sarcomas (HSs), 7 interdigitating dendritic cell sarcomas (IDCSs), and 10 Langerhans cell sarcomas (LCSs), underwent hybridization capture with analysis of up to 406 cancer-related genes. RESULTS: Among the entire cohort of 102 patients, CDKN2A mutations were most frequent across subtypes and made up 32% of cases, followed by TP53 mutations (22%). Mitogen-activated protein kinase (MAPK) pathway mutations were present and enriched among the malignant histiocytosis (M) group (HS, IDCS, and LCS) but absent in FDCS (72% vs. 0%; p < .0001). In contrast, NF-κB pathway mutations were frequent in FDCSs but rare in M group histiocytoses (61% vs. 12%; p < .0001). Tumor mutational burden was significantly higher in M group histiocytoses as compared with FDCSs (median 4.0/Mb vs. 2.4/Mb; p = .012). We also describe a pediatric patient with recurrent secondary histiocytic sarcoma treated with targeted therapy and interrogated by molecular analysis to identify mechanisms of therapeutic resistance. CONCLUSION: A total of 42 patient tumors (41%) harbored pathogenic mutations that were potentially targetable by approved and/or investigative therapies. Our findings highlight the potential value of molecular testing to enable precise tumor classification, identify candidate oncogenic drivers, and define personalized therapeutic options for patients with these aggressive tumors. IMPLICATIONS FOR PRACTICE: This study presents comprehensive genomic profiling results on 102 patient cases within four major subtypes of malignant histiocytic and dendritic cell neoplasms, including 44 follicular dendritic cell sarcomas (FDCSs), 41 histiocytic sarcomas (HSs), 7 interdigitating dendritic cell sarcomas (IDCSs), and 10 Langerhans cell sarcomas (LCSs). MAPK pathway mutations were present and enriched among the malignant histiocytosis (M) group (HS, IDCS, and LCS) but absent in FDCSs. In contrast, NF-κB pathway mutations were frequent in FDCSs but rare in M group histiocytosis. A total of 42 patient tumors (41%) harbored pathogenic mutations that were potentially targetable by approved and/or investigative therapies.

18F-AV-1451 positron emission tomography in neuropathological substrates of corticobasal syndrome.

Multiple neuropathological processes can manifest in life as a corticobasal syndrome. We sought to relate retention of the tau-PET tracer 18F-AV-1451 and structural magnetic resonance measures of regional atrophy to clinical features in clinically diagnosed and neuropathologically confirmed cases of corticobasal syndrome and to determine whether these vary with the underlying neuropathological changes. In this observational, cross-sectional study, 11 subjects (eight female and three male, median age 72 years) with corticobasal syndrome underwent structural MRI, tau-PET with 18F-AV-1451, amyloid-PET with 11C-Pittsburgh compound B, detailed clinical examinations and neuropsychological testing. Of the 11, three had evidence of high amyloid burden consistent with Alzheimer's disease while eight did not. Neuropathological evaluations were acquired in six cases. Mixed effects general linear models were used to compare 18F-AV-1451 retention and atrophy in amyloid-negative corticobasal syndrome cases to 32 age-matched healthy control subjects and to relate cortical and subcortical 18F-AV-1451 retention and atrophy to clinical features. Subjects without amyloid, including three with pathologically confirmed corticobasal degeneration, showed greater regional 18F-AV-1451 retention and associated regional atrophy in areas commonly associated with corticobasal degeneration pathology than healthy control subjects [retention was higher compared to healthy controls (P = 0.0011), driven especially by the precentral gyrus (P = 0.011) and pallidum (P < 0.0001), and greater atrophy was seen in subjects compared to control subjects (P = 0.0004)]. Both 18F-AV-1451 retention and atrophy were greater in the clinically more affected hemisphere [on average, retention was 0.173 standardized uptake value ratio units higher on the more affected side (95% confidence interval, CI 0.11-0.24, P < 0.0001), and volume was 0.719 lower on the more affected side (95% CI 0.35-1.08, P = 0.0001)]. 18F-AV-1451 retention was greater in subcortical than in cortical regions, P < 0.0001. In contrast to these findings, subjects with amyloid-positive corticobasal syndrome, including two neuropathologically confirmed cases of Alzheimer's disease, demonstrated greater and more widespread 18F-AV-1451 retention and regional atrophy than observed in the amyloid-negative cases. There was thalamic 18F-AV-1451 retention but minimal cortical and basal ganglia uptake in a single corticobasal syndrome subject without neuropathological evidence of tau pathology, likely representing non-specific signal. Asymmetric cortical and basal ganglia 18F-AV-1451 retention consonant with the clinical manifestations characterize corticobasal syndrome due to corticobasal degeneration, whereas the cortical retention in cases associated with Alzheimer's disease is greater and more diffuse.

Fatal GNAQ-mutated CNS melanoma in an adolescent with nevus of Ota.

Nevus of Ota is an uncommon benign mesodermal melanosis that involves the first and second divisions of the trigeminal nerve. Primary non-cutaneous melanoma often involves distinct genetic mutations compared to cutaneous melanoma. In primary central nervous system (CNS) melanomas associated with nevus of Ota, somatic mutations most commonly occur at the Q209 and R183 residues of GNAQ and likely induce tumorigenesis through upregulation of the MAP kinase pathway. This case underscores the importance of elucidating neurologic symptoms early in patients with nevus of Ota, as a delayed presentation of CNS melanoma could portend a devastating outcome.

A Simplified Brain Blocking Protocol Optimized for the Diagnosis of Neurodegenerative Disease Saves Time and Money While Preserving Anatomic Relationships.

CONTEXT.­: Postmortem evaluation for neurodegenerative disease is expensive in time and materials. These challenges can be met by implementing simpler sampling protocols while preserving anatomic relations. OBJECTIVE.­: To determine the diagnostic effectiveness and cost-effectiveness of a simplified brain blocking protocol compared with the standard blocking protocol used in our Alzheimer's Disease Research Center (ADRC). DESIGN.­: We prospectively compared the neuropathologic diagnoses established from our standard 19-cassette/19 brain sites ADRC protocol to a simplified 6-cassette/12 brain sites protocol in 52 consecutive cases. The simplified protocol generated 14 slides for comparison to 52 slides from our standard protocol. RESULTS.­: Compared with the ADRC protocol the simplified protocol produced Alzheimer Disease Neuropathologic Changes probability scores that were the same in 50 of 52 cases (r = 0.99). Staging for Lewy pathology was equivalent in 45 of 52 (r = 0.98), scoring for cerebral amyloid angiopathy was equivalent in 48 of 52 (r = 0.97), and grading for arteriolosclerosis was the same in 45 of 52 cases (r = 0.92). Progressive supranuclear palsy (n = 4), multiple system atrophy (n = 2), and corticobasal degeneration (n = 1) could be diagnosed by either protocol independently. The estimated savings per case was 72% or $1744.89 ($2436.37 [ADRC] versus $691.48 [simplified]). CONCLUSIONS.­: The diagnosis of neurodegenerative disease at autopsy can be done accurately with a less expensive, simplified protocol. Our protocol is similar to those of previously published approaches, but it has a simpler organization scheme. This method should be valuable to institutions where autopsy cost considerations may be important.

Secondary Involvement of the Uterine Cervix by Nongynecologic Neoplasms: A Detailed Clinicopathologic Analysis.

Secondary involvement of the uterine cervix by nongynecologic neoplasms is rare accounting for <2% of metastases to the gynecologic tract. This study aimed to analyze the clinicopathologic features of cervical involvement by nongynecologic malignancies. A total of 47 cases were identified including 39 (83%) carcinomas, 6 lymphomas (12.8%), and 2 (4.2%) cutaneous malignant melanomas. The most common primary site of origin among carcinomas was the gastrointestinal tract (27, 69.2%), followed by breast and urothelium (5 each, 12.8%), gallbladder, and lung (1 each, 2.6%). The gynecologic tract was involved at the presentation in 16 patients (34%), including 5 (10.6%) with the cervix being the first site, 7 (14.9%) with synchronous involvement of the cervix and other gynecologic sites, and 4 (8.5%) with the involvement of other gynecologic sites before the cervical presentation. Patients with lymphoma were younger compared with those with carcinoma (43.7 vs. >50.5) (P=0.01). Mean time to identification of cervical metastases was <1 year for gallbladder carcinoma, melanomas, and gastrointestinal signet ring cell carcinomas (P=0.03). Features that varied with different types of metastatic tumor included lymphovascular space invasion, depth of stromal invasion, growth pattern (glands lacking architectural complexity, cribriforming, solid), presence of goblet cells, and signet ring cells, degree of cytologic atypia, and overall findings mimicking a benign/noninvasive process (P≤0.027). Six tumors (12.8%) were initially misdiagnosed as cervical primary. Metastatic nongynecologic tumors can mimic primary in situ or invasive neoplasms in both ectocervix and endocervix. In patients with a known prior malignancy, the clinical history with ancillary studies and a high level of suspicion are crucial to ensure accurate diagnosis.

Myelofibrosis and Portal Hypertension: The Case for Primary Variceal Screening.

Myelofibrosis is a hematologic condition that predisposes to the formation of large and small portal venous clots. Portal injury is believed to underlie the mechanism of development of noncirrhotic portal hypertension in this population. We describe a patient with myelofibrosis, proven portal hypertension, and extramedullary hematopoiesis with no imaging or pathologic evidence of microvascular or macrovascular portal clot. We provide a concise review of the literature which highlights that patients with myelofibrosis and related conditions of polycythemia vera and essential thrombocytosis present not infrequently with portal hypertension and variceal bleeding. We propose this population may benefit from primary variceal screening.

Solitary fibrous tumor involving the pancreas: report of the cytologic features and first report of a primary pancreatic solitary fibrous tumor diagnosed by fine-needle aspiration biopsy.

INTRODUCTION: Solitary fibrous tumor (SFT) of the pancreas is rare, with only 16 reported cases in English studies. The cytologic features of pancreatic SFT have not been well described. We report 2 cases of SFT (1 primary and 1 metastatic) involving the pancreas and discuss the cytomorphologic findings, including the first primary SFT of the pancreas specifically diagnosed using cytology. MATERIALS AND METHODS: The cases of 2 patients with a diagnosis of SFT of the pancreas from material obtained via fine needle aspiration (FNA) are reported. Clinical information was retrieved from the patients' medical records. The FNA cytology slides, previous relevant surgical pathologic findings, and findings from subsequent pancreatic resections were reviewed. RESULTS: Of the 2 patients, 1 had had secondary involvement of the pancreas from a primary central nervous system SFT, and 1 had had a primary pancreatic SFT diagnosed by FNA. Immunohistochemistry for STAT6 was crucial for establishing the diagnosis using FNA. CONCLUSIONS: We have reported 2 cases of SFT involving the pancreas, including the first reported case of primary pancreatic SFT diagnosed preoperatively using FNA. Metastatic SFT from central nervous system primaries should be considered when diagnosing SFT of the pancreas.

Identification of recurrent FHL2-GLI2 oncogenic fusion in sclerosing stromal tumors of the ovary.

Sclerosing stromal tumor (SST) of the ovary is a rare type of sex cord-stromal tumor (SCST), whose genetic underpinning is currently unknown. Here, using whole-exome, targeted capture and RNA-sequencing, we report recurrent FHL2-GLI2 fusion genes in 65% (17/26) of SSTs and other GLI2 rearrangements in additional 15% (4/26) SSTs, none of which are detected in other types of SCSTs (n = 48) or common cancer types (n = 9,950). The FHL2-GLI2 fusions result in transcriptomic activation of the Sonic Hedgehog (SHH) pathway in SSTs. Expression of the FHL2-GLI2 fusion in vitro leads to the acquisition of phenotypic characteristics of SSTs, increased proliferation, migration and colony formation, and SHH pathway activation. Targeted inhibition of the SHH pathway results in reversal of these oncogenic properties, indicating its role in the pathogenesis of SSTs. Our results demonstrate that the FHL2-GLI2 fusion is likely the oncogenic driver of SSTs, defining a genotypic-phenotypic correlation in ovarian neoplasms.

Premature vascular disease in young adult stroke: a pathology-based case series.

INTRODUCTION: The prevalence of modifiable vascular risk factors is increasing in young adults and may contribute to the growing frequency of stroke in this population. The neuropathology and end-organ damage profile of young adult stroke patients with clinically advanced atherosclerosis or arteriosclerosis has not been studied. METHODS: This retrospective study included patients aged 18-60 years admitted to our hospital from 1995 to 2017 with recurrent ischemic or hemorrhagic strokes, fatal stroke, or stroke associated with advanced small vessel disease (SVD) on brain MRI, who had no evidence for structural, genetic, inflammatory, or infectious etiology for stroke, and had adequate pathological materials available for analysis. The presence of atherosclerosis, arteriolosclerosis, left ventricular hypertrophy, and nephrosclerosis was evaluated. RESULTS: Twelve patients (mean age 47 ± 9 years, range 31-57 years, 67% male) met inclusion criteria. Four had fatal intracerebral hemorrhage (ICH), three had recurrent non-fatal ICH, one had ICH with advanced SVD on MRI, and four had recurrent ischemic strokes including two with transient ischemic attacks. Pathological studies showed moderate/severe atherosclerosis in 64% and moderate/severe arteriolosclerosis in 42% of patients. Pathological data to evaluate end-organ damage were available for nine patients; eight showed left ventricular hypertrophy and all showed nephrosclerosis. CONCLUSION: Young adult stroke patients with recurrent stroke, fatal stroke, or SVD on imaging have advanced atherosclerosis and arteriolosclerosis-related pathological changes in multiple organ systems. Aggressive control of atherosclerosis risk factors is warranted even in young individuals.

Single-cell sequencing of neonatal uterus reveals an Misr2+ endometrial progenitor indispensable for fertility.

The Mullerian ducts are the anlagen of the female reproductive tract, which regress in the male fetus in response to MIS. This process is driven by subluminal mesenchymal cells expressing Misr2, which trigger the regression of the adjacent Mullerian ductal epithelium. In females, these Misr2+ cells are retained, yet their contribution to the development of the uterus remains unknown. Here, we report that subluminal Misr2+ cells persist postnatally in the uterus of rodents, but recede by week 37 of gestation in humans. Using single-cell RNA sequencing, we demonstrate that ectopic postnatal MIS administration inhibits these cells and prevents the formation of endometrial stroma in rodents, suggesting a progenitor function. Exposure to MIS during the first six days of life, by inhibiting specification of the stroma, dysregulates paracrine signals necessary for uterine development, eventually resulting in apoptosis of the Misr2+ cells, uterine hypoplasia, and complete infertility in the adult female.

PGR Gene Fusions Identify a Molecular Subset of Uterine Epithelioid Leiomyosarcoma With Rhabdoid Features.

Genetic aberrations among uterine epithelioid leiomyosarcomas are unknown. Following identification of an index case with NR4A3-PGR fusion demonstrating monomorphic morphologic features, we interrogated additional uterine tumors demonstrating similar histology and sought to describe the morphologic and immunohistochemical characteristics of PGR-rearranged sarcomas. Targeted next-generation RNA sequencing was performed on RNA extracted from formalin-fixed paraffin-embedded tissue of the index case. Fluorescence in situ hybridization using custom probes flanking PGR and NR4A3 genes was applied to 17 epithelioid leiomyosarcomas, 6 endometrial stromal tumors, and 3 perivascular epithelioid cell tumors. NR4A3-PGR fusion (n=4) and PGR rearrangement (n=2) were detected in 6 (35%) epithelioid leiomyosarcomas. Median patient age was 45 years, and all presented with FIGO stage I or II tumors, 2 being alive with disease at 75 and 180 months. All tumors were centered in the cervical stroma or myometrium and consisted of cells with abundant eosinophilic cytoplasm (epithelioid), including many displaying dense intracytoplasmic inclusions (rhabdoid). Myxoid matrix and hydropic change imparted a microcystic growth pattern in 4 tumors. Five also showed a minor spindle cell component which was low-grade in 3, consisting of bland spindle cells with low mitotic activity. High-grade spindle cell morphology was seen in 2 tumors, exhibiting a storiform pattern of atypical spindle cells associated with brisk mitotic activity. Desmin, estrogen receptor, and progesterone receptor were positive in all 6 tumors, while CD10 and HMB45 were negative. PGR rearrangements define a genetic subset of epithelioid leiomyosarcomas with often biphasic morphology consisting of epithelioid and rhabdoid as well as spindle cell components.

Pelvic and pulmonary benign metastasizing leiomyoma: A case report.

Seven years after she had a total abdominal hysterectomy for benign leiomyomas, a 46-year-old woman presented with a pelvic mass and multiple pulmonary nodules. She underwent resection of the mass and core needle biopsy of a pulmonary lesion. Histopathologic analysis revealed that both the pelvic and the pulmonary lesions were consistent with benign leiomyomas. Benign metastasizing leiomyoma should be considered if a woman of reproductive age and with a history of leiomyomas presents with extrauterine nodules without evidence of malignancy. The final diagnosis should be based on histopathological examination. Treatment depends on tumor size, location, receptor positivity, and disease progression.

Cost-effectiveness of IDH testing in diffuse gliomas according to the 2016 WHO classification of tumors of the central nervous system recommendations.

BACKGROUND: Due to the decreasing prevalence of IDH1 mutations in older patients, the 2016 World Health Organization (WHO) classification of brain tumors proposed not to perform sequencing for isocitrate dehydrogenase (IDH) in glioblastoma patients ≥55 years old. We present a cost-effectiveness analysis to estimate the financial impact of these guidelines. METHODS: From 2010 to 2015 we performed 1023 IDH tests in gliomas, amounting to ~$1.09 million in direct laboratory test costs. Samples were tested using R132H-specific immunohistochemistry, DNA sequencing validated for detection of noncanonical IDH1/2 mutations, or both methods. RESULTS: In cases tested by DNA sequencing, the fraction of non-R132H mutations was 5.4%, which included only 2 high-grade gliomas in patients ≥55 years (0.9%). When remodeling the optimal age cutoff in our patient population using 5-year age-binning, we found a 10-times higher pretest probability for the presence of a noncanonical IDH1 mutation in the setting of a negative IDH1-R132H immunohistochemistry result in patients <55 years. Applying the independently confirmed age cutoff of 55 years to glioblastoma patients (64%) would result in $403200 saved (43%). By not performing sequencing in patients ≥55 years, the turn-around time to final integrated neuropathological diagnosis is reduced by 53%, allowing these patients to gain earlier benefits from personalized genomic medicine. CONCLUSION: The negligible prevalence of noncanonical IDH mutations in glioblastoma patients ≥55 years argues against universal IDH sequencing in this population. We predict that adoption of this age-based sequencing cutoff recommendation from the 2016 WHO guidelines will result in significant cost and time savings throughout the global health care system.

Brief overview of selected approaches in targeting pancreatic adenocarcinoma.

INTRODUCTION: Pancreatic adenocarcinoma (PDAC) has the worst prognosis of any major malignancy, with 5-year survival painfully inadequate at under 5%. Investigators have struggled to target and exploit PDAC unique biology, failing to bring meaningful results from bench to bedside. Nonetheless, in recent years, several promising targets have emerged. AREAS COVERED: This review will discuss novel drug approaches in development for use in PDAC. The authors examine the continued efforts to target Kirsten rat sarcoma viral oncogene homolog (KRas), which have recently been successfully abated using novel small interfering RNA (siRNA) eluting devices. The authors also discuss other targets relevant to PDAC including those downstream of mutated KRas, such as MAPK kinase and phosphatidylinositol 3-kinase. EXPERT OPINION: Although studies into novel biomarkers and advanced imaging have highlighted the potential new avenues toward discovering localized tumors earlier, the current therapeutic options highlight the fact that PDAC is a highly metastatic and chemoresistant cancer that often must be fought with virulent, systemic therapies. Several newer approaches, including siRNA targeting of mutated KRas and enzymatic depletion of hyaluronan with PEGylated hyaluronidase are particularly exciting given their early stage results. Further research should help in elucidating their potential impact as therapeutic options.