Pathology and cancer

ALSO KNOWN AS: Pathobiology, anatomical pathology, clinical pathology

DEFINITION: Pathology is a science that seeks to understand the changes in function and structure of organs, tissues, cells, and body fluids that lead to disease and death. The word “pathology” comes from the Greek word pathos, meaning feeling, pain, or suffering, and the suffix ology, which signifies “the study of.”

In concert with the scientists and technicians who assist them, pathologists investigate the nature and causes of disease in anatomical and metabolic systems at molecular and genetic levels. These molecular-level processes must be fully understood to diagnose a disease. An accurate differential diagnosis is the basis for the choice of therapy and potential return to health.

Anatomical pathology, the study of structural and cellular changes in disease processes, includes surgical pathology; autopsy services that identify clues for the coroner or medical examiner, who determines causes of death; and forensic pathology, which provides the scientific link between medicine and the law.

Clinical pathology focuses on the cellular and chemical changes in body cells and fluids that differentiate health from disease and includes the disciplines of microbiology, immunology, hematology, immunohematology/blood banking/transfusion services, and chemistry.

Subspecialties: Pathology is a unique specialty because pathologists do not typically see a patient but instead consult with the patient’s physician. Pathology includes ten certifiable clinical and anatomical subspecialties at the physician level. Clinical pathology specialties are blood banking/transfusion medicine/immunohematology, chemical pathology, hematology, medical microbiology, and molecular genetics and are supported by clinical laboratory scientists and technicians. Anatomical pathology specialties are cytopathology, dermatopathology, neuropathology, pediatric pathology, and forensic pathology and are supported by pathology assistants, histologists, cytologists, and cytogeneticists.

Anatomical pathology. In the case of tumor removal, the surgical pathologist looks at the margins of the excision and tells the surgeon if they are clean (free of cancer). The surgical pathologist informs the surgeon if the entire tumor has been removed, whether the lymph nodes are involved and whether the tissue is metastatic—a manifestation of malignancy as a secondary growth arising from the primary tumor. In this way, the surgical pathologist plays a pivotal role in determining what the surgeon will ultimately choose as the next step.

When tissue is removed, it is passed to the histology department, where histologists stabilize it by fixation. The tissue is then immersed in multiple baths to dehydrate and clear it and finally impregnate it with wax. After embedding, sectioning, and staining, the tissue is once again reviewed by the pathologist, who often determines whether cancer or particular receptors for cancer, such as HER2/neu, are present.

In cytopathology, anatomical pathologists work closely with cytologists who process, stain, and review all cell preparations. These specialists study cell structures, cell composition, cell interaction with other cells, and the larger environment in which cells exist. Cytologists look for too many of one kind of cell or note when a particular cell type is missing. Suspicious smears are referred to the pathologist.

One common cytological procedure is the Pap test, the medical screening method to detect premalignant and malignant changes in the ectocervix. The Pap smear is a routine procedure during a woman’s annual gynecological examination. The cytologist looks at the cell structures to detect the early formation of cancer cells. Early detection leads to greater survival rates.

Clinical pathology. In the clinical laboratory, thousands of medical tests are available, including those designed to diagnose and track cancer. Examples include tests for cancer antigens (CA), alpha-fetoprotein (AFP), carcinoembryonic (CEA), lipid-associated sialic acid (LASA), prostate-specific antigen (PSA), and the T-lymphocyte cluster of differentiation (CD) markers.

General chemistry and hematology tests identify cancers or may function to demonstrate the degree to which the body tolerates therapies and guide the patient’s physician in making adjustments to treatment. As genomics and proteomics become more commercially available, the clinical laboratory will provide personalized profiles that will permit the treating physician to tailor therapies specific to a particular cancer and the individual for more effective protocols leading to a cure.

New and potentially useful markers for cancer diagnoses are continuously being discovered. Time and tedious research are required to determine which ones will result in earlier diagnoses, increasingly targeted and cost-effective treatment, and ultimately, prevention.

Training and certification: Although pathology departments are in the background, away from the public eye, they are complex, multifaceted operations supporting the practitioners who care for patients. Directors of full-service laboratories must be licensed physicians or individuals who have earned a doctor of philosophy degree in chemical, physical, biological, or clinical laboratory science.

Certified pathologists are licensed physicians who have first graduated from an approved medical school or college of osteopathic medicine and select specialty training in a pathology residency program accredited by the Accreditation Council for Graduate Medical Education or the Royal College of Physicians and Surgeons of Canada. After three or four years of graduate medical education, candidates pass an objective written and practical examination.

Certified pathologists are licensed physicians who have first graduated from an approved medical school or college of osteopathic medicine and who select specialty training in a pathology residency program that is accredited by the Accreditation Council for Graduate Medical Education or the Royal College of Physicians and Surgeons of Canada. After three or four years of graduate medical education, candidates pass an objective written and practical examination.

There are three pathology certificationsanatomic pathology (AP), clinical pathology (CP), and combined anatomic pathology and clinical pathology (AP/CP).

Within the pathology department are cadres of scientists and specialists in chemistry, microbiology, hematology, transfusion service, immunology, cytology, and histology, with certifications that require baccalaureate and associate degrees.

Services and procedures performed: In addition to performing surgical diagnostic procedures, anatomical pathologists examine tissue acquired through biopsy from all parts of the body. After grossly examining the specimen, histologists prepare tissue slides that are then stained and reviewed by the pathologist for a final diagnosis.

The clinical pathologist is responsible for the quality assurance of all the biological tests performed in the chemistry, hematology, immunology, immunohematology, and microbiology laboratories. These responsibilities include method selection, quality control, and interpretation of test results.

Forensic pathologists are trained to assist law enforcement in homicide cases. They establish the cause of death, estimate the time of death, infer the type of weapon used, distinguish homicide from suicide, establish the identity of the deceased, and determine the effect of trauma or preexisting conditions on the consequential death.

Related specialties and subspecialties: Pathologists, clinical laboratory scientists, cytologists, cytogeneticists, histologists, pathology assistants, and phlebotomists work as a team to deliver diagnostic and monitoring laboratory test results to the primary care physicians who interact with patients and their families. Each professional group has academic, certification, and continuing education requirements to support changing and emerging practices in the specialty.

Clinical laboratory scientists have bachelor’s degrees, and clinical laboratory technicians have associate degrees. Both are certified to perform chemistry, microbiology, hematology, transfusion services, and immunology testing procedures. Phlebotomists may be certified to collect blood and other body fluids for analysis in clinical laboratories.

Histologists are technologists with associate or bachelor’s degrees who are certified to process, embed, stain, and cut tissue to the thickness of a single layer to demonstrate the cellular morphology, chemical composition, and function of normal and abnormal tissue.

Cytologists, cytogeneticists, and pathology assistants have bachelor’s degrees and certifications. Cytologists are trained to process and prepare cells for review. Suspicious cells are passed to pathologists for final identification. Cytogeneticists are trained to process cells and thus reveal information coded in the chromosomes to describe the individual's heredity as this information relates to particular diseases. Pathology assistants are trained to provide anatomical services under the direction of a pathologist, including the gross examination of surgical pathology specimens and autopsies.

Bibliography

Benson, Ellis S., et al. Career Guide in Pathology. Amer. Soc. for Clinical Pathology, 1998.

Biddinger, Paul W., et al. Diagnostic Pathology and Molecular Genetics of the Thyroid: A Comprehensive Guide for Practicing Thyroid Pathology. 3rd ed., Wolters Kluwer, 2020.

Borri, Filippo, and Annarita Granaglia. "Pathology of Triple Negative Breast Cancer." Seminars in Cancer Biology, vol. 72, 2021, pp. 136-145. doi.org/10.1016/j.semcancer.2020.06.005.

Coppola, Domenico. Molecular Pathology and Diagnostics of Cancer. Springer, 2014.

Pagana, Kathleen Deska, and Timothy J. Pagana. Mosby’s Diagnostic and Laboratory Test Reference. 7th ed., Elsevier, 2022.

Rothschild, Bruce M., et al. Modern Paleopathology: The Study of Diagnostic Approach to Ancient Diseases, Their Their Pathology and Epidemiology: Let There Be Light, the Light of Science and Critical Thinking. Springer, 2023. 

Sadowski, Elizabeth A., et al. "PET/MR Imaging in Gynecologic Cancer: Tips for Differentiating Normal Gynecologic Anatomy and Benign Pathology Versus Cancer." Abdominal Radiology, vol. 2022, pp. 1-16. doi.org/10.1007/s00261-021-03264-9.

Sherbet, G. V. Therapeutic Strategies in Cancer Biology and Pathology. Elsevier, 2013.

"Understanding Your Pathology Report." American Cancer Society, www.cancer.org/cancer/diagnosis-staging/tests/biopsy-and-cytology-tests/understanding-your-pathology-report.html. Accessed 20 July 2024.