Pancreatic Tumors. Группа авторов

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СКАЧАТЬ least seven passes are made from the pancreatic lesion [12–15]. A meta-analysis review concluded that ROSE does not improve EUS-FNA adequacy in pancreatic masses [16]. Hence, routine use of ROSE in EUS-FNA at tertiary cancer centers may not change clinical outcomes. This study also concluded that, since ROSE is a time-consuming service with poor reimbursement and is not available in many centers, it should not be strongly recommended for all EUS-FNA procedures for pancreatic lesions [16]. Non-assisted EUS-FNA procedures incur lower costs and a comparable rate of complications.

      Performing ROSE

      A staff member from the clinical team/cytotechnologist/cytopathologist assists in specimen collection during the procedure and with smear preparation in the procedure room or suite. At our institution two slides are prepared from each pass. One slide is air dried for Diff-Quik staining and the second slide is fixed in 95% alcohol for later Papanicolaou (PAP) staining in the laboratory. The needle is rinsed in balanced salt solution for cell block processing. The Diff-Quik-stained slide is used for on-site morphological evaluation of adequacy. Additional needle passes are performed based on the assessment of the Diff-Quik-stained smears, and material collected for additional ancillary studies based on the on-site adequacy.

      Stains

The stains used for on-site adequacy depend on the institution. Some centers use an alcohol-fixed slide and stain it with rapid hematoxylin and eosin (HE). Other centers may use a rapid PAP or a different type of Romanowsky stain [17]. PAP staining is the standard at most institutions for the alcohol-fixed slides and is used for the final interpretation.

      Collection Media

If ancillary studies are needed, additional dedicated passes for cell block material are made. Different types of collection mediums, such as saline, Roswell Park Memorial Institute (RPMI), neutral-buffered formalin, a mixture of formalin and 95% ethanol, and methanol, are available and can be utilized for needle rinses. Specimens collected in saline and RPMI can be used for flow cytometry if needed. Needle rinses can be processed into cell blocks or cytospin slides if the material collected is scant. Needle rinses collected in preservatives containing alcohol (methanol in PreservCyt and ethanol in SurePath Preservative Fluid) can be processed using ThinPrep® and SurePathTM respectively. Although ThinPrep preparation is being used for pancreatic FNAs, there are certain pitfalls and limitations to it. It is difficult to recognize mucin on ThinPrep slides and mucinous neoplasms may be incorrectly diagnosed. A study by de Luna et al. [18] concluded that the diagnostic accuracy of pancreatic FNA using ThinPrep is inferior to that of conventional smears. However, ThinPrep® remains a viable substitute for smear preparation for practices in which a cytologist is not available on-site to prepare the slides. At our institution, we receive pancreatic FNA specimens submitted directly into CytoLyt, and have found them to have a good diagnostic yield. Aspirates form cysts have been identified to have background mucin and the epithelium is well preserved.

      Cell Blocks

      A good cell block preparation can be utilized for additional ancillary studies such as immunohistochemical stains, fluorescence in situ hybridization, and other molecular studies necessary for the diagnosis and treatment of the patients. Ancillary tests that are validated for formalin-fixed specimens may have to be revalidated for specimens that are fixed in alcohol. Alcohol-fixed specimens may have altered antigenicity which may render some of the tests falsely negative.

Different cell block preparation methods utilize different collection mediums for transportation and fixation of the specimen collected, for example methanol is used as a fixative for the automated Cellient cell block technique [19]. Other methods of cell block preparation are the clot and scrape method, BBC cell block fixative method, plasma thrombin cell block preparation, collodion bag cell block procedure, Shandon cytoblock method, HistoGel method, Tissue coagulum clot method, and Formalin or alcohol vapor method [19]. The clot and scrape method and formalin/alcohol vapor method are both inexpensive techniques but are reported to have variable quality and cellularity. The collodion method, although time consuming, has a good cellular yield, making it ideal for samples with scant cellularity. Collodion is admixed with an ether-based solvent; it must be handled in a laminar flow hood and stored in small volumes in a flameproof enclosure [20]. The Cellient automated system is time consuming and expensive but is great for small/scanty samples and provides a crisp cellular architecture. As it is fully automated, there is little chance of cross-contamination. It utilizes methanol as the fixative which could interfere with certain immunohistochemical stains. However, in a separate protocol formalin can be used as the fixative. The instrument can accommodate only one specimen block at a time, so high-volume labs may require multiple instruments. The HistoGel method is tedious but helps in the concentration of cells and provides good cellular preservation. The plasma thrombin method is an inexpensive and simple method and provides a clean background. The disadvantages of this technique include an inability to control clot formation and irregular distribution of cells within the pellet. Some thromboplastin agents contain epithelial cells that may interfere with the diagnosis and with the interpretation of ancillary studies [21].

      Processing of Cytology Samples from Pancreatic Cystic Lesions

The goal of pancreatic cyst fluid evaluation is to differentiate mucin from non-mucinous lesions, and to identify cysts carrying a high-risk malignancy [22, 23]. Hence, both symptomatic and asymptomatic pancreatic cysts are actively evaluated to determine the nature of the cyst. It is extremely crucial to examine the cyst fluid aspirated to make this distinction and to rule out high-grade dysplasia or adenocarcinoma associated with the cyst.

      Pancreatic cyst fluids need to be submitted fresh and undiluted. The pancreatic cyst fluid needs to be triaged for biochemical analysis, to include carcinoembryonic antigen (CEA) and amylase, and for molecular analysis, in addition to cytology. CEA and amylase can be performed from the supernatant, which is preferred, as it preserves the cells in the specimen for cytological evaluation.

Chai et al. [24] developed a volume-based protocol using minimal pancreatic cyst fluid volumes for biochemical, molecular, and cytology analysis. The addition of molecular analysis to the traditional CEA and cytological examination of the pancreatic cyst fluid has led to a reappraisal of how these samples are triaged and the comparative roles of these different modalities [25, 26]. Ideally, if the cyst fluid volume is sufficient it is split into neat (unaltered fluid), smears, cell block, and supernatant fluid. Chai et al. [24] proposed the following pancreatic cyst fluid triage based on volume:

Fig. 3. СКАЧАТЬ