A biopsy is a critical medical procedure used to identify and diagnose cancerous cells or other abnormal conditions in the body. It involves the collection of tissue samples from areas suspected of being affected. The journey of a biopsy sample through laboratory processing is a carefully orchestrated process that requires precision and expertise. Let's delve deeper into each step of this informative journey:
Who examines a biopsy sample?
After a biopsy procedure, where affected tissue is excised for analysis, the sample is sent to a specialized pathology laboratory. Here, a pathologist, a medical professional specialized in studying tissues and organs, takes charge of running tests and analyzing the sample for diagnosis. The pathologist's expertise is crucial in determining the nature and extent of any abnormalities in the tissue.
How is the biopsy sample analyzed?
Sample Preservation
Upon arrival at the pathology laboratory, the tissue sample is immediately placed in a container filled with formaldehyde or formalin—a solution of formaldehyde in water. Formalin serves as a fixative that penetrates the tissue, binding to specific amino acids, and cross-linking with them. This process preserves the overall structure of the sample and prevents decay. Formalin also hardens the tissue, making it easier to cut thin sections for microscopic examination.
Other fixatives, such as Bouin solution and B5 (consisting of mercuric chloride, sodium acetate, and formaldehyde), are used for specific purposes.
Bouin solution offers sharp penetration of hematoxylin and eosin staining, enabling better visualization of cellular structures. However, it has the disadvantage of degrading DNA and RNA.
B5 fixative is ideal for preserving lymph nodes and spleen samples and allows for rapid fixation while maintaining detailed tissue structures. However, due to the presence of mercury, additional disposal protocols must be followed. Glutaraldehyde fixative is used for tissues intended for examination under an electron microscope.
Sample Labeling
Before any further processing takes place, the biopsy sample is meticulously labeled. The label includes essential patient information such as the patient's name, date of birth, and site from which the sample was excised. Proper labeling is crucial for accurate identification and traceability of the sample throughout the entire laboratory process.
Gross Examination
Once the sample is properly preserved and labeled, it undergoes a gross examination. During this step, the pathologist observes the tissue specimen without a microscope. This preliminary examination provides the pathologist with a general idea of the area of concern within the sample, its size, and consistency. Gross examination typically takes 3-4 days for larger tissue samples, allowing the pathologist to identify specific regions of interest for further analysis under a microscope.
Processing
After the gross examination, the tissue sample is processed to prepare it for microscopic examination. The first step involves embedding the tissue in hot paraffin wax, creating a solid block. Thin slices, usually less than 1 cm in thickness, are then cut from the paraffin-embedded block using a specialized instrument called a microtome. These thin slices enable clear visualization of cellular structures under a microscope.
The tissue slices are then stained, using various dyes, which enhance contrast and highlight specific cellular features. This staining process improves the visibility of different cell types and their characteristics, aiding the pathologist in making an accurate diagnosis. Before sectioning and staining, the tissue may need to be dehydrated and cleared, which can take around 12 hours. The entire processing procedure, including embedding in paraffin wax and staining, takes approximately 16 hours. Special stains may require an additional 1-5 days.
Frozen Section: In some situations, a frozen section examination is required, particularly during surgery. In this case, a portion of the tissue is immediately frozen in a special solution that forms a cube around the tissue. The frozen tissue is then sliced using a machine called a cryostat, and the thin sections are stained and examined under a microscope. While this method provides rapid results to aid decision-making during surgery, it may not be as detailed as the analysis of tissues embedded in paraffin wax.
Microscopic Examination
The most critical step in the biopsy lab analysis is the microscopic examination. The pathologist carefully examines the stained tissue sections under a microscope to assess cellular characteristics. The primary objective is to determine whether the cells are cancerous or show signs of other abnormalities. If cancer is present, the pathologist notes additional information, such as the grade of cancer (how abnormal the cells appear), tumor margins (whether the cancerous cells are well-defined or have spread into surrounding tissue), cancer stage (extent of cancer's spread), and the severity of the disease.
The microscopic examination is an intricate and time-consuming process that typically takes one day after the gross examination. The pathologist's keen observations and expertise play a crucial role in accurate diagnosis and, consequently, effective treatment planning for the patient.
Conclusion
The journey of a biopsy sample through laboratory processing is a meticulous and complex procedure. Each step, from sample preservation to the final microscopic examination, involves skilled professionals working together to ensure accurate and timely diagnosis. The biopsy lab analysis plays a pivotal role in identifying cancer and other diseases, providing essential information for planning appropriate treatment strategies. The thorough and precise analysis of biopsy samples helps medical professionals offer personalized and effective care to patients, enhancing the chances of successful treatment and recovery.
