Molecules and markers for endosonographers: What do we need to know and measure?

Abstract

IntroductionEndoscopic ultrasound (EUS) has become an indispensable tool for the diagnosis and staging for gastrointestinal and thoracic malignancies. Thanks to the safety and reliability of fine needle aspiration (FNA), this has become the method of choice for tissue acquisition from lymph nodes and tumors in various locations within the thoracic and abdominal cavities.In the recent years, EUS-FNA has offered a better understanding of the pathophysiology of cancer. Similar to the adenoma-carcinoma sequence, other cancers including pancreas, lung, and esophagus may follow a comparable multi-step process of carcinogenesis. A necessary component of these is the ability to go ªbeyond cytologyº to use fine needle aspirates to characterize the genomic and proteomic profiles of cancer and precancerous tissue. Molecular characterization of FNA samples: The basic conceptsAlthough DNA is relatively stable in excised tissue, proteins and particularly RNA are unstable and must be handled in special ways to preserve them for characterization. The first role of the endoscopist is to obtain and preserve tissue suitable for further molecular characterization. In the first part of this review, we will focus on these initial steps. The methods for genomic and proteomic analyses are beyond the scope of this article and interested readers are referred to recent reviews [1,2].RNA destroying-enzymes (RNAase enzymes) are very ubiquitous in the environment. Therefore, it is imperative to prevent rapid degradation of RNA in order to preserve fine needle aspirates for genomic studies. The simplest method to do this is through the use of RNAase inhibitor solutions such as RNA-later (Quagen Inc. Valencia Ca, USA) or RNA Stat 60 (RNA STAT-60 ; TEL-TEST, Friendswood, TX, USA). The needle aspirate can be quickly mixed with these reagents. In our laboratory, we immediately place the FNA sample into an eppendorf tube in a wet ice bath, centrifuge in a small desktop device in the EUS room (1000 RPM at 4 deg. C, 1 minute), remove the supernatant, and resuspend the cell pellet in RNA stat 60. If RNA stabilization is not available on-site, the aspirate can also be snap frozen in liquid nitrogen and stored (preferably at ±70 to ±80C) for later RNA stabilization. Every effort should be made to handle the specimen in an RNAase-free environment including clean gloves and a surface that has been cleaned with an RNAase inhibitor solution.In the remainder part of this review, we will focus on organspecific applications of the biological markers. This will include lesions of the pancreas and gastrointestinal stromal tumors (GIST). The use of biomarkers in staging non-small call lung cancer will be discussed in a separate review. Pancreatic lesionsDiagnosis of early pancreatic cancer remains a challenge mainly due to the lack of a standard screening test. Therefore, improving long-term survival relies primarily on detecting and treating early pancreatic cancer and thus reducing the incidence of pancreatic cancer.EUS is increasingly considered a valuable to...

Endosonografische Differenzialdiagnose von Pankreastumoren

“…! Die EUS-FNA weist in der Diagnostik des Adenokarzinoms des Pankreas eine hohe Sensitivität (80 -90%) und Spezifität (> 95 %) auf [196 -199] [186,204,205]. In einer kürzlich erschiedenen Untersuchung waren K-ras-Punktmutationen im EUS-FNA-Material aus 74 % der Adenokarzinome des Pankreas, jedoch aus keiner fokalen entzündlichen Pankreasläsion nachweisbar [201].…”