Cell-blocks and immunohistochemistry

Abstract

The interpretation of results on immunostained cell-block sections has to be compared with the cumulative published data derived predominantly from formalin-fixed paraffin-embedded (FFPE) tissue sections. Because of this, it is important to recognize that the fixation and processing protocol should not be different from the routinely processed FFPE surgical pathology tissue. Exposure to non-formalin fixatives or reagents may interfere with the diagnostic immunoreactivity pattern. The immunoprofile observed on such cell-blocks, which are not processed in a manner similar to the surgical pathology specimens, may not be representative resulting in aberrant results. The field of immunohistochemistry (IHC) is advancing continuously with the standardization of many immunomarkers. A variety of technical advances such as multiplex IHC with refined methodologies and automation is increasing its role in clinical applications. The recent addition of rabbit monoclonal antibodies has further improved sensitivity. As compared to the mouse monoclonal antibodies, the rabbit monoclonal antibodies have 10 to 100 fold higher antigen affinity. Most of the scenarios involve the evaluation of coordinate immunostaining patterns in cell-blocks with relatively scant diagnostic material without proper orientation which is usually retained in most of the surgical pathology specimens. These challenges are addressed if cell-blocks are prepared with some dedicated methodologies such as NextGen CelBloking™ (NGCB) kits. Cell-blocks prepared by NGCB kits also facilitate the easy application of the SCIP (subtractive coordinate immunoreactivity pattern) approach for proper evaluation of coordinate immunoreactivity. Various cell-block and IHC-related issues are discussed in detail.

Immunocytochemistry of effusions: Processing and commonly used immunomarkers

“…is simple SCIP approach is especially rewarding in unexpected situations especially when immunostaining pattern is not straightforward and needs careful scrutiny. [1,2] Sections of cell-blocks (3-4 µm) are mounted on chargecoated slides and immunostained with a routine protocol following standard precautions and guidelines for quality control. [15]…”

Comparison of programmed death ligand 1 immunostaining for pancreatic ductal adenocarcinoma between paired cytological and surgical samples

“…Endoscopic ultrasound-guided fine-needle aspiration (FNA) of pancreatic tumors has become the standard method for diagnosing PDAC. [ 22 ] Thus, frequently the only tissue available to evaluate PD-L1 expression comes from cytological samples, underscoring the urgency to standardize these samples for biomarker analysis.…”

CytoJournal monographs: First CMAS (CytoJournal Monograph/Atlas Series) on science of cell-block making, titled “CellBlockistry 101 (Text Book of Cell-blocking science)”

“…In keeping with the CMAS guidelines, all of these chapters have been published as six different review articles under open access in CytoJournal. [5][6][7][8][9][10] Subsequently, these articles would be modified slightly to format them as different chapters of the monograph as allowed under the Creative Commons License. [3] is first monograph is supported by limited funding from the Late Geeta Paradkar Memorial Fund.…”