As pathology is a largely unknown field in medicine, we are glad that Dr José Cândido Xavier Jr., a specialist in surgical, dermato- and cytopathology, agreed to shed light on “The role of a pathologist in diagnosis and treatment”. This is the third part of our series.

Pathology is a varied medical field. As previously mentioned in our series, medicine is like a tree, in which the roots are the basic sciences (physiology, genetics, cellular biology, anatomy, histology, and so on), and the twigs are the medical specialties (dermatology, gynecology, urology, gastroenterology, hematology, etc.). The sub-specialties of pathology provide the connection between the trunk and the twigs. For example, dermatopathology connects general pathology with clinical dermatology. Dermatopathologists study diseases related to the skin, including abnormal growth of tissue, infections, inflammation, bullous conditions, autoimmune diseases, and pathophysiological processes like aging.

In the same way, hematopathology studies diseases and processes related to blood cells, bone marrow, the spleen, and lymph nodes. This sub-specialty also deals with lymphomas outside of lymph nodes in tissue like skin, mucosa, and other organs. There are many different sub-areas of pathology, including gynecopathology, ocular pathology, head and neck pathology, bone and soft tissue pathology, cytopathology, and others. Sub-specialization allows pathologists to become experts in a specific area.

Considering all pathological fields, cytopathology deserves a specific explanation. Cytopathology does not focus on one organ or system. Cytopathologists analyze smears, not formalin-fixed and paraffin-embedded samples. They do not examine the tissue itself; instead, they study cells prepared on slides. Dr. Papanicolaou famously studied the cytology of the uterine cervix in the last century. The Pap smear or Pap test, which is a test for cervical cancer, is named after him.

In recent decades, some protocols were developed to standardize the cytopathological findings and reports for many materials (e.g., the Bethesda system for thyroid cytopathology, the Milan system for salivary gland cytopathology, the Paris system for urinary cytopathology, etc.). Cytological specimens can be collected with a swab, cytobrush, or fine needle aspiration.

To illustrate the breadth of pathology, let’s take the example of breast cancer because it is one of the most widespread and fatal cancers worldwide. Can you imagine that the most recent World Health Organization book (part of a series called the WHO Blue Books) about breast tumor classification runs more than 300 pages and lists more than 70 distinct conditions and tumors from malignant to benign? Medicine and pathology are constantly evolving. Over time, researchers uncover findings that allow precise tumor classification, and new entities are discovered that make cancer classification a dynamic process. Without exaggeration, every human tissue can generate an abnormal growth of tissue; if there are cells, there is a chance of cancer.

From epidemiological studies, we can infer that some cancers are age-related. For example, nephroblastoma, a malignant kidney tumor, most frequently affects children. Prostate cancer, by contrast, usually occurs in the 50s and most frequently after 60 years of age. So, pathology can help guide public health policies toward high-risk people. Even though most cancers have a familial relationship (meaning that if my father had prostate cancer, I have a higher chance of prostate cancer than the ordinary population), most malignant tumors are not related with genetic heritage syndromes (germinative mutation).

Some tumors are associated with risk factors; for example, smoking is related to lung and oral cancer. We also know that there is a relationship between some viruses (like human papillomavirus and Epstein-Barr virus) and cancer. Sun exposure is a primary cause of skin cancer.

Although the understanding of cancer is increasing, much remains to do. Most cancers have no established risk factors or causes. These gaps reinforce the importance of pathology in medicine. Despite the challenges of our specialty, our primary job is to help generate accurate diagnoses to ensure patients receive appropriate treatment and live their best lives.