Examining breast cells under a microscope is a fundamental and longstanding method used to identify and understand the presence of breast cancer. This microscopic evaluation provides detailed information about the cellular changes indicative of malignancy, guiding subsequent medical decisions.
Why Microscopic Examination is Essential
Microscopic examination plays a foundational role in breast cancer diagnosis by definitively confirming the presence of cancerous cells. It distinguishes between benign (non-cancerous) and malignant (cancerous) conditions. Furthermore, it enables the initial classification of the cancer type, such as whether it originated in the milk ducts (ductal carcinoma) or milk-producing lobules (lobular carcinoma), and if it is confined to its original location (in situ) or has spread into surrounding tissue (invasive). This information guides further testing and treatment planning.
How Breast Cells Are Prepared for Viewing
Preparing breast tissue or cell samples for microscopic examination involves several precise laboratory steps. The process typically begins with obtaining a tissue sample, often through a biopsy, such as a core needle biopsy. Once collected, the tissue undergoes fixation, a process where it is immersed in a chemical solution, commonly formalin, to preserve its structure.
Following fixation, the tissue is processed and embedded, usually in paraffin wax, to create a solid block that can be thinly sliced. This block is then sectioned into extremely thin slices, typically around 5 micrometers thick, using a specialized instrument called a microtome. These slices are then placed onto glass slides. Finally, the slides are stained with various dyes, most commonly Hematoxylin and Eosin (H&E), to make the different cellular components visible under a light microscope. Hematoxylin stains cell nuclei a purplish-blue, while Eosin stains the cytoplasm and extracellular matrix pink, allowing for clear differentiation of cellular structures.
Distinguishing Features of Cancer Cells
When viewed under a microscope, breast cancer cells exhibit several distinguishing morphological features that set them apart from healthy cells. These characteristics are key indicators for pathologists. One prominent feature is pleomorphism, which refers to significant variation in the size, shape, and staining intensity of both the cancer cells and their nuclei. Unlike uniform healthy cells, malignant cells often appear highly irregular and diverse in appearance.
Nuclear abnormalities are another hallmark. The nuclei of breast cancer cells are often enlarged, irregular in shape, and may stain darker than normal nuclei, a condition known as hyperchromasia. They may also contain prominent nucleoli, which are small structures within the nucleus. These nuclear changes are considered important diagnostic markers.
Cancer cells also display increased mitotic activity, meaning they divide more frequently and abnormally. Pathologists look for the presence of numerous mitotic figures, which are cells actively undergoing division, and may also observe abnormal mitotic forms. This elevated rate of cell division contributes to the rapid and uncontrolled growth characteristic of tumors.
A loss of polarity and organization is another key feature. Normal breast cells are arranged in an organized, structured manner within ducts and lobules, maintaining distinct top and bottom orientations (polarity). Cancer cells often lose this organized architecture, appearing disorganized. This disruption of normal tissue structure is a clear sign of malignancy.
Invasive breast cancer cells demonstrate invasion, breaking through the normal tissue boundaries and spreading. This indicates that the cancer cells have acquired the ability to move beyond their original location, which is a step in cancer progression and metastasis. The presence of cancer cells infiltrating adjacent structures, rather than remaining confined, confirms an invasive process.
The Pathologist’s Contribution to Diagnosis
The pathologist plays a central role in interpreting the microscopic findings and rendering a definitive breast cancer diagnosis. They synthesize all observed cellular and architectural features to classify the type of breast cancer, such as invasive ductal carcinoma or ductal carcinoma in situ. This classification helps determine the cancer’s origin and behavior.
In addition to classification, pathologists assign a grade to the tumor, often using systems like the Nottingham grade, which assesses how aggressive the cells appear based on features like tubule formation, nuclear pleomorphism, and mitotic activity. This grading provides an indication of the tumor’s potential growth rate and likelihood of spreading.
Pathologists also perform additional microscopic tests, such as immunohistochemistry (IHC), on the same tissue slides. IHC helps identify specific protein markers on cancer cells, such as estrogen receptors (ER), progesterone receptors (PR), and HER2 status. The presence or absence of these markers is crucial for guiding targeted treatment decisions, as certain therapies are effective only against cancers expressing specific receptors. The comprehensive report generated by the pathologist, detailing the cancer type, grade, and molecular markers, is an essential document that directly guides the patient’s clinical management and treatment strategy.