Tutorial

Pathology

Physicians working in pathology labs are responsible for morphologic diagnosis. They examine biological materials, describing structural modifications occurring during tumor development. When browsing the following items you will better understand the work of the pathologists in cancer's morphologic diagnosis.

  • The cancer diagnosis includes pathologic analysis of surgical specimens. It should describe the structural changes observed in a biopsy sample or in an entire surgical removed organ. Samples are also observed under the microscope, describing changes in cells arrangements. A tumor sample is called biopsy, when only a small tissue fragment has been sent to the laboratory. Usually, most oncologic surgeries provide the entire organ for pathologic exam. The pathologic exam is usually described in a written report, which is forwarded to the attending physician. When the material comes from a tumor's fine needle aspiration, the examination is limited to the identification of cells clusters and the method is called cytopathology.

  • It is the part of the pathologic examination in which the physician describes changes in the form of the examined material, without using optical devices. Gross examination allows the pathologist to select the most representative areas of the disease, which are sampled and prepared for microscopic exam.

  • It is the part of the pathologic examination in which samples selected during gross examination are prepared for analysis under a microscope. This preparation preserves the tissue using dehydration followed by embedding with paraffin wax. The specimen forms a block that could be sectioned with a microtome, producing a very thin section that is placed in a microscopy slide. After staining and preparation, the glass slide is examined under the optical microscope. In almost all cases, pathologic diagnosis is clarified by the use of a simple and universal staining technique called haematoxylin-eosin (HE). This technique could be refined using monoclonal antibodies, increasing the diagnostic specificity.

  • Consists of an extension of the pathologic examination in which the expression of molecular markers is used to infer the cell biological behavior. The technique is based on binding monoclonal antibodies with specific cellular markers. For example, breast cancer cells expressing receptors for estrogen or progesterone are identified and quantified by immunohistochemistry. The ki67 evaluation indicates cellular proliferation and tumor's aggressiveness. 

  • Medicine has advanced a lot in this area. More recently, it has being described genomic profiles, which provides a better understanding of tumor biological behavior. Tumorigenesis could occur as a consequence of increasing numbers of copies of an oncogene, a phenomenon called amplification. Alternatively, a mutation in tumor suppressor gen could elicit a loss in its protection function. In breast cancer, for example, a set of genetic tests (Oncotype 21 and Mamma-Print) allows to infer many aspects of tumor aggressiveness, leading to improvements in treatment guidance. Additionally, mutations in BRCA1 and BRCA2 suppressor genes could make the patient more prone to develop breast cancer.