A Narrative Review of Lung Cancer Cytology in the Times of Coronavirus

What Physicians Should Know

Pasquale Pisapia; Umberto Malapelle; Maria Salatiello; Rafael Rosell; Giancarlo Troncone

Disclosures

Transl Lung Cancer Res. 2020;9(5):2074-2081. 

In This Article

Biosafety and ROSE

Respiratory cytological samples can be obtained by a number of sampling procedures that are usually less invasive than the histological approaches.[27] Cytological procedures can exploit the possibility to monitor in real time the quality in terms of informativeness of the obtained material.[27] In fact, these minimal invasive procedures are much more cost-effective when associated to ROSE.[27] This is key since these procedures are not always well tolerated by the patients and reducing the number of passes is mandatory when performing FNA during computed tomography (CT), magnetic resonance imaging (MRI), endoscopy ultrasound (EUS) and endobronchial US (EBUS).[28] ROSE allows not only to check sample adequacy to establish a microscopic diagnosis but also to ensure that tissue material is sufficient to perform ancillary techniques, including immunohistochemistry, microbiology studies, flow cytometry analysis, and molecular assays.[29] However, aerosols or droplets may be generated in different steps during the ROSE workflow; in fact, contamination may occur when the tissue material is forced to be expelled from the needle or syringe, when smearing the material, when air-drying the slides, in particular if the smears are agitated by hand. Ideally, these procedures should be performed under class II BSC.[9,17] However, such equipment that are available in most pathology laboratories are not commonly found in the radiological or endoscopic suites. Thus that, it is mandatory that the healthcare providers protect themselves with PPE. These latter include eye protection, water-resistant, long-sleeve gown covers, shoe covers, and gloves. EU FFP2 masks or a higher level of protection are used for EBUS transbronchial needle aspiration procedures.[17]

Usually, ROSE is performed on air-dried Diff Quik stained smears; during the current healthcare emergency this method may represent a biosafety risk not only for the droplets and aerosol generation from unfixed smears but also for the inherent features of the Diff Quik method (Figure 1B,C,D).[30] This rapid method is a Romanowski group of stains derivate that requires methanol fixation (reagent A), eosin (reagent B) and methylene blue (reagent C) staining. Usually, slides are briefly fixed in 80% methanol solution reagent A for 20 to 40 seconds, which is not effective in inactivating the SARS-CoV-2.[16,30] Even longer fixation times (60 to 90 seconds) are not sufficient whereas longer treatments may result into cell damage and fixation artifacts.[16,30] As an alternative in most institutions, rapid Pap stain is used; this method requires alcohol fixation of the smears, with sub-sequential hematoxylin, OG-6 and EA-50 treatments, with the excess of staining quickly removed by 1% acetic acid.[30] A better morphological preservation may be obtained by the ultrafast Pap staining, that, however, requires longer times of smear air-drying which makes more common do loss of cellular details. Alternatively, rapid hematoxylin and eosin (H&E) staining offers the advantage of immediate alcohol fixation and of high standard of morphological preservation. Another possible solution to Diff Quik stain is the cheap, available, and rapid toluidine blue method, although most pathologists are not familiar with this staining. As a general rule, air-dried specimens should be limited and methanol fixation avoided.[30]

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