Introduction: Cytopathology is an important part of pathology that is used to diagnose disease on the cellular level. The application of the cell block (CB) technique plays a vital role in cytological diagnosis, as blocks and slides can be further used for special stains, immunohistochemistry (IHC), and molecular pathological analysis. Several methods for making CBs have been reported, but their procedures and cellular yield are still deemed unsatisfactory. In this article, we used gellan gum (GG) as an adjuvant for CBs, which resulted in higher cellular yield with simpler procedures.
Methods: CBs were prepared by using GG, copper sulfate, plasma/thrombin, or pregelatinized starch methods. The procedures of each of these four methods were then compared. CB sections were stained with hematoxylin and eosin (H&E), and the background and morphological features seen by H&E staining were compared. A preliminary IHC and fluorescence in situ hybridization (FISH) study was performed using cytology specimens from eleven and five cases, respectively. The expression of immunocomplex by IHC and the molecular signals detected by FISH were compared in CB sections made by the four methods and a section derived from the biopsy specimen block from the same patient. Feulgen staining, Alcian blue staining, and Masson trichrome staining were performed on the CB sections from 3 cases of pleural fluid. The cellular yield of CB sections from 83 cases according to the four methods was compared using NDP analysis software.
Results: The results demonstrated that sections derived from CBs made with GG had a clear background and good morphological features by H&E staining. The expression of immunocomplex by IHC and the molecular signals of FISH detection in the sections from CBs made by GG were accurately located just as those in biopsy sections from the same patient. The DNA, acidic mucus, and fibrin could be clearly identified through special stains in the CB sections. The procedures involved in the GG method were easily controllable and the coagulated gel increased the ease by which the CB was embedded and sectioned. Specifically, sections from CBs made by the GG method contained higher cellular yield because cells could be concentrated on the bottom of the gel after centrifugation.
Conclusion: This novel method for making CBs is a practical, simple method that can result in higher cellular yield. This method is therefore worth promoting in clinical applications.
Keywords: cell block; cellular yield; cytological specimens; cytology; gellan gum.
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