Macrodissection is a technique used across biological and medical fields to prepare tissue samples for various analytical procedures. This method ensures that analyses are performed on the most relevant parts of a tissue specimen, making its application widespread in research and clinical diagnostics.
Understanding Macrodissection
Macrodissection is a manual technique used to isolate specific areas of interest from larger tissue samples. This process is performed without a microscope or specialized equipment, relying on visual identification of the target tissue. It differs from microdissection, like laser capture, which isolates individual cells under high magnification. Macrodissection focuses on larger, macroscopically distinguishable regions within a tissue section.
The technique is suitable for uniform tissue sections, such as large tumors with clearly visible boundaries. While macrodissection enriches the desired tissue, it does not completely eliminate non-tumor material. Its goal is to enrich the tissue of interest by excluding unwanted tissue, reducing background noise from irrelevant cells.
The Purpose of Macrodissection
Macrodissection is performed to ensure the accuracy and reliability of subsequent diagnostic and molecular analyses. By isolating specific diseased cells or particular tissue types from surrounding healthy or irrelevant tissue, it prevents contamination that could skew results. This isolation is especially important for molecular tests, where even a small amount of contaminating normal tissue can dilute the genetic material from the target cells.
For example, in tumor analysis, macrodissection helps enrich the percentage of tumor cells within a sample. This enrichment is important because non-tumor material can affect genomic studies, potentially altering the interpretation of genetic mutations or other pathological features. By removing confounding non-tumor material before nucleic acid extraction, macrodissection increases the purity of extracted DNA or RNA, leading to more accurate diagnostic calls. Studies show macrodissection can change subtype or genetic translocation status calls, improving diagnostic precision.
How Macrodissection is Performed
The general process of macrodissection involves visually identifying and manually cutting out the target tissue from a prepared slide or tissue block. Initially, a pathologist reviews a hematoxylin and eosin (H&E)-stained slide, which serves as a reference. On this stained slide, the pathologist identifies and marks the region of interest, such as a tumor area.
This marked H&E-stained slide is then aligned with an unstained slide containing serial sections from the same tissue block. Using a razor blade or scalpel, the desired region is carefully scraped or cut from the unstained slide, guided by the markings on the reference slide. The dissected tissue is then transferred into a microcentrifuge tube for further processing, often using a wet pipette tip for easy collection. This manual, visually guided approach makes macrodissection a straightforward and cost-effective method.
Role in Biological and Medical Analysis
Macrodissection is important in pathology, research, and molecular diagnostics by providing precisely isolated tissue samples for various analyses. The enriched tissue is then used for procedures such as DNA, RNA, and protein extraction, which are important for advanced molecular testing. These extracted biomolecules are subsequently subjected to genetic sequencing, gene expression profiling, and protein analysis.
The data obtained from these analyses inform disease diagnosis, prognosis, and guide personalized treatment strategies. For instance, genetic profiling of tumors, made more accurate by macrodissection, has become routine for various cancers, including non-small cell lung cancer and prostatic carcinoma. This technique contributes to personalized medicine by improving understanding of disease mechanisms and identifying specific biomarkers that predict treatment response. By maximizing the neoplastic cellularity in a sample, macrodissection enhances the sensitivity of molecular analyses, reducing the need for additional biopsies and supporting targeted therapies.