Quality Management of the Immunohistochemistry Laboratory: A Practical Guide

Brazilian Expert Consensus for NTRK Gene Fusion Testing in Solid Tumors

Oncogenic neurotrophic tropomyosin receptor kinase gene fusions occur in less than 1% of common cancers. These mutations have emerged as new biomarkers in cancer genomic profiling with the approval of selective drugs against tropomyosin receptor kinase fusion proteins. Nevertheless, the optimal pathways and diagnostic platforms for this biomarker's screening and genomic profiling have not been defined and remain a subject of debate. A panel of national experts in molecular cancer diagnosis and treatment was convened by videoconference and suggested topics to be addressed in the literature review. The authors proposed a testing algorithm for oncogenic neurotrophic tropomyosin receptor kinase gene fusion screening and diagnosis for the Brazilian health system. This review aims to discuss the latest literature evidence and international consensus on neurotrophic tropomyosin receptor kinase gene fusion diagnosis to devise clinical guidelines for testing this biomarker. We propose an algorithm in which testing for this biomarker should be requested to diagnose advanced metastatic tumors without known driver mutations. In this strategy, Immunohistochemistry should be used as a screening test followed by confirmatory next-generation sequencing in immunohistochemistry-positive cases.

Highlights from the 7th Oncological Pathology Conference 'Pathological Anatomy in the context of the National Cancer Law: An overview of the Latin American experience', 15, 22 and 23 July 2022, Trujillo, Peru

The seventh session of the Oncological Pathology Conference (JoPaO) entitled 'Pathological Anatomy in the context of the National Cancer Law: An overview of the Latin American experience', was held virtually on July 15, 22 and 23. Peru was the headquarters for this event, where 17 national and international professors of high academic standing participated. They interacted in a multidisciplinary context through talks with national panellists and the general public. The recent promulgation of the 'National Cancer Law' fosters the development of discussion forums to analyse the national realities and uphold continuous learning about experiences in other Latin American countries with successful cancer programmes, in which pathology holds a principal role. The topics addressed during this JoPaO included the exchange of Latin American cancer management experiences, an emphasis on investments in and the development of strategic plans to improve care, the use of new technologies, laboratory quality control, and the need to advance scientific research.

Immunohistochemistry, Quality Control, and Principles of Validation in the Central Nervous System

The conventional hematoxylin and eosin stain (H&E) is vital for the histological diagnosis but the role of immunohistochemistry (IHC) in the central nervous system is undeniable. Immunohistochemical techniques detect antigens in tissue sections by immunological and chemical reactions. This chapter reviews the preanalytic, analytic, and postanalytic phases of immunohistochemistry, as well as the principles of quality control and validation.

Development of novel quality control material based on CRISPR/Cas9 editing and xenografts for MLH1 protein deficiency testing

BACKGROUND

Mismatch repair deficiency (dMMR) status induced by MLH1 protein deficiency plays a pivotal role in therapeutic decision-making for cancer patients. Appropriate quality control (QC) materials are necessary for monitoring the accuracy of MLH1 protein deficiency assays used in clinical laboratories.

METHODS

CRISPR/Cas9 technology was used to edit the MLH1 gene of GM12878Cas9 cells to establish MLH1 protein-deficient cell lines. The positive cell lines were screened and validated by Sanger sequencing, Western blot (WB), and next-generation sequencing (NGS) and were then used to prepare formalin-fixed, paraffin-embedded (FFPE) samples through xenografting. These FFPE samples were tested by hematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) for suitability as novel QC materials for MLH1 protein deficiency testing.

RESULTS

We successfully cultured 358 monoclonal cells, with a survival rate of 37.3% (358/960) of the sorted monoclonal cells. Through Sanger sequencing, cell lines with MLH1 gene mutation were identified. Subsequently, two cell lines with MLH1 protein deficiency were identified by WB and named as GM12878Cas9_6 and GM12878Cas9_10. The NGS results further confirmed that the MLH1 gene mutation in these two cell lines would cause the formation of stop codons and terminate the expression of the MLH1 protein. The H&E staining and IHC results also verified the deficiency of the MLH1 protein, and FFPE samples from xenografts proved their similarity and consistency with clinical samples.

CONCLUSIONS

We successfully established MLH1 protein-deficient cell lines. Followed by xenografting, we developed novel FFPE QC materials with homogenous, sustainable, and typical histological structures advantages that are suitable for the standardization of clinical IHC methods.

p57 in Hydatidiform Moles: Evaluation of Antibodies and Expression in Various Cell Types

Supplemental Digital Content is available in the text.

The protein p57 is encoded by CDKN1C. This gene is known to be paternally imprinted and maternally expressed in cytotrophoblasts and villous stromal cells. We present a method for evaluating p57 antibodies (Abs) in hydatidiform mole (HM) and demonstrate the results for 4 p57 Abs in various cell types. Five cases of complete HM, diploid with 2 paternal genome sets (CHM;PP), 5 cases of partial HM, triploid with 2 paternal and 1 maternal genome sets (PHM;PPM), and 5 cases of non-HM, with diploid biparental genomes (non-HM;PM) were stained with p57 Abs: 57P06, EP183, KP10, and KP39. Assessment of the fraction of nuclei stained, and the intensity of staining of the nuclei and cytoplasm was performed. For evaluation of the Abs, the observations in cytotrophoblasts, villous stromal cells, maternal decidual cells, and intermediate trophoblasts were scored. The fraction of stained nuclei in cytotrophoblasts and villous stromal cells and the staining of cytoplasm showed to be important parameters in the evaluation of the Abs. 57P06 was evaluated as optimal. KP10 showed moderate cytoplasmatic staining in maternal decidual cells and intermediate trophoblasts, and was evaluated as good. EP183 was evaluated as poor, primarily due to nuclear staining in ≥10% of the villous stromal cells in CHM;PP. KP39 was evaluated as poor, primarily due to strong cytoplasmatic staining in some cytotrophoblasts and villous stromal cells. A structured testing of p57 for diagnosing HM is recommended. No nuclear staining was observed in syncytiotrophoblasts of CHM;PP, indicating that in syncytiotrophoblasts also, CDKN1C is paternally imprinted.

Evaluation of Formalin Fixation for Tissue Biopsies Using Shear Wave Laser Speckle Imaging System

Chemical fixation is the slowest and often the most uncontrolled step in the multi-step process of preparing tissue for histopathology. In order to reduce the time from taking a core needle biopsy to making a diagnosis, a new approach is proposed that optically monitors the common formalin fixation process. A low-cost and highly-sensitive laser speckle imaging technique is developed to measure shear wave velocity in a biospecimen as small as 0.5 mm in thickness submerged in millifluidic channels. Shear wave velocity, which is the indicator of tissue mechanical property and induced by piezoelectric-actuation, was monitored using gelatin phantom and chicken breast during fixation, as well as post-fixed liver and colon tissues from human. Fixation levels in terms of shear wave velocity increased by approximately 271.0% and 130.8% in gelatin phantom and chicken breast, respectively, before reaching the plateaus at 10.91 m/s and 7.88 m/s. Within these small specimens, the plateaus levels and times varied with location of measurement, and between gelatin and chicken breast. This optical-based approach demonstrates the feasibility of fine-tuning preanalytical variables, such as fixation time, for a rapid and accurate histopathological evaluation; provides a quality metric during the tissue preparation protocol performed in most pathology labs; and introduces the millifluidic chamber that can be engineered to be a future disposable device that automates biopsy processing and imaging.

Uneven Staining in Automated Immunohistochemistry: Cold and Hot Zones and Implications for Immunohistochemical Analysis of Biopsy Specimens

OBJECTIVES

The occurrence of uneven staining (UES) in automated immunohistochemistry (IHC) has been experienced by clinical laboratories and has the potential to confound readout, interpretation, and reporting of IHC assays despite the presence optimally stained on-slide controls. However, there are no studies of this phenomenon in regard to the type, frequency, and association with different automated IHC platforms. We studied the occurrence of UES in automated IHC assays with real world examples from clinical practice and by using a laboratory developed methodology to monitor baseline and periodic performance of automated IHC instruments.

MATERIALS AND METHODS

Sections of formalin-fixed, paraffin-embedded normal liver tissue were mounted on 180 glass slides and stained for HepPar1 on 6 automated IHC instruments (4 different models from 3 different manufacturers). Macroscopic and microscopic defects of staining were recorded.

RESULTS

Only 8% of slides showed completely uniform staining. UES, including areas of both increased and decreased staining, occurred with all instruments. Decreased staining was often zonal, involving large regions of the slide. Decreased staining mostly localized in an instrument-dependent manner. Increased staining tended to occur in small foci with a random distribution.

CONCLUSIONS

The common occurrence of UES (particularly decreased staining) has important implications for the reliable read-out of IHC assays on biopsy samples. Baseline and periodic quality assurance testing for UES is recommended for all automated IHC instruments.

Proposals for best-quality immunohistochemical staining of paraffin-embedded brain tissue slides in forensics

Immunohistochemistry (IHC) has become an integral part in forensic histopathology over the last decades. However, the underlying methods for IHC vary greatly depending on the institution, creating a lack of comparability. The aim of this study was to assess the optimal approach for different technical aspects of IHC, in order to improve and standardize this procedure. Therefore, qualitative results from manual and automatic IHC staining of brain samples were compared, as well as potential differences in suitability of common IHC glass slides. Further, possibilities of image digitalization and connected issues were investigated. In our study, automatic staining showed more consistent staining results, compared to manual staining procedures. Digitalization and digital post-processing facilitated direct analysis and analysis for reproducibility considerably. No differences were found for different commercially available microscopic glass slides regarding suitability of IHC brain researches, but a certain rate of tissue loss should be expected during the staining process.