Pre-made recipient wax blocks facilitate tissue microarray standardization and internal quality control in the pathology department.

Background of the need for standardized quality control in pathology departments

In tests such as immunohistochemistry and in situ hybridization, pathology departments need to set up positive, negative, and tissue-type controls. Traditional manual section controls often have inconsistencies in section thickness, tissue size, and positioning. Tissue microarray technology integrates multiple tissue samples into the same paraffin block, enabling synchronous detection of multiple tissues on the same slide and helping to reduce operational differences between different sections. Prefabricated recipient paraffin blocks serve as the basic carrier for tissue microarrays and provide the prerequisite for the above standardized operations.

In routine work, pathology departments can use prefabricated recipient paraffin blocks to pre-design array templates and then implant screened donor tissue cores into the corresponding wells. This not only improves the regularity of array arrangement but also facilitates subsequent digital scanning and image analysis.

Role in antibody validation and staining quality control

Antibody validation is an important part of immunohistochemistry quality control. Multi-tissue arrays constructed using prefabricated recipient paraffin blocks allow the staining pattern of the same antibody in multiple tissue types to be observed simultaneously on one slide. It is generally recommended to include known positive tissue cores, negative tissue cores, and tissue cores to be validated in the array so that comparisons can be made under the same staining conditions.

Because the wells of prefabricated recipient paraffin blocks are fixed in advance, the positions of the tissue cores are relatively consistent, making localization and interpretation after staining easier. In internal quality control, quality control chips prepared from prefabricated recipient paraffin blocks can be incorporated into the daily staining workflow to regularly evaluate staining intensity and background conditions, helping to identify batch-to-batch differences in reagents or operational fluctuations. However, it should be noted that quality control results should be interpreted in combination with morphological evaluation and the laboratory's established standards, and conclusions should not be drawn based on a single result alone.

Array design and commonly used control settings

When designing arrays on prefabricated recipient paraffin blocks, pathology departments generally plan according to the detection indicators and sample types. Common practices include:

Partitioning by tissue type: such as epithelial tissue, mesenchymal tissue, lymphohematopoietic tissue, etc., to facilitate observation of antibody specificity.

Setting positive control sites: selecting tissue cores with relatively stable expression validated in the past.

Setting negative control sites: selecting tissue cores of the corresponding tissue type that are expected not to express or to show low expression.

Reserving blank or marker sites: used for localization and orientation recognition to avoid mirror-image misinterpretation.

It is not recommended that the array arrangement be too dense, so as to avoid mutual compression of tissue cores or interference from staining diffusion. Well spacing and well diameter should be comprehensively determined in combination with section thickness, tissue core diameter, and scanning equipment resolution.

Storage and information management

After sectioning quality control chips prepared from prefabricated recipient paraffin blocks, the recipient paraffin blocks and the corresponding donor paraffin block information should be properly preserved. It is recommended to establish electronic or paper records, including paraffin block numbers, array layout, tissue source, pathological diagnosis, section thickness, and staining conditions, etc. The storage environment for paraffin blocks generally requires a cool, dry, and dark place to avoid deformation of the paraffin blocks caused by high temperatures. Remaining tissue microarray paraffin blocks can be used for subsequent counterstaining, additional sectioning, or methodological comparison, but the integrity of the paraffin blocks and the status of the array should be checked regularly.