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 second part of our series.

Why Is There a Need for a Pathology Report?

All cancer diagnoses require a pathology report. These reports provide critical information that guides treatment and follow-up in addition to diagnosing the tumor. To design a treatment plan, oncologists and surgeons must scrutinize the pathology report. They also take advantage of auxiliary techniques which can be applied to pathological specimens and might provide prognostic features (i.e., if the cancer is aggressive or not) and predictive features (e.g., whether a tumor has a good chance of responding to a specific drug). These features can be identified by microscopic analysis, additional immunohistochemistry techniques, or molecular examinations.

The pathology report is a medical document that consists of four parts:

• Demographic information
• Clinical information
• Macroscopic report
• Microscopic report

The first part contains the patient’s demographic information (name, date of birth, age, procedure date, and others). Nowadays, these reports often include a barcode to serve as a unique identifier.

The second part documents the clinical information, which means the general medical history of the patient. Pathology reports are based on clinical-pathological correlations. That’s why the final diagnosis considers not only what is found on the slides but also the patient’s background and medical history.

I will use a report about melanoma as an example. It is important to mention that melanoma is a malignant tumor that most frequently affects the skin and carries a poor prognosis when diagnosed in an advanced stage. Therefore, what the doctor sees through the dermoscope as well as the history of a spot or lesion (i.e., if the lesion is new or shows color changes during follow-up) are essential to a pathological diagnosis.

These findings are complemented by the macroscopic report (third part) with the gross description of the specimen. For example, considering the product of skin tumor extraction, the report includes the size of the specimen, the size of the visible tumor, its color, and the distance to the margins of the biopsy specimen.

The final and most crucial part is the microscopic report (fourth part), including the diagnosis and related features. A pathology report of a melanoma will provide a list of more than ten topics, including:

• histological subtype (i.e., if it is a variant related to sun exposure or not);
• the Breslow index (the most relevant staging parameter for melanoma), which will indicate in millimeters how deep the tumor cells in the skin are;
• possible invasion of vessels and/or nerves;
• the presence or absence of ulceration (abscess) and its extension;
• possible regression which means tumor remission (focal disappearance) at some point;
• possible brisk inflammatory infiltration around the tumor or not.

In conclusion, we can say that patients with high Breslow index and/or tumor ulceration and/or vascular invasion have poor prognoses and short overall survival.

What Does Tumor Staging Mean?

Aside from that, tumor staging is applied to pathological analyses of surgical excision (not for biopsies) and indicates how advanced the tumor is. Again, in melanoma cases, the tumor’s thickness (Breslow index) and ulceration define the tumor stage. The staging system might be based on other parameters in other organs and tumor subtypes. The stage is one reason patients with the same tumor have different disease histories. For example, consider two female patients of the same age and similar health status. If one patient has a breast tumor that is 5 cm in diameter and the other has a tumor of 1 cm, even if both tumors have the same histological and immunohistochemistry profile, the patient with a more extensive tumor has a worse prognosis, meaning a lower chance of surviving 5/10 years.

In summary, a tumor staging system classifies different patients with the same tumor at distinct levels of risk. Staging can be based on tumor size (such as in the breast) or the tissue level of involvement (such as in melanoma). However, the stage is not solely based on tumor characteristics. It also applies to lymph node status (i.e., if there is metastasis to the local lymph nodes) and metastasis to distant organs. This tumor staging system is called TNM:

• T = Tumor
• N = Node
• M = Metastasis

In this way, the staging combines pathological, clinical, and radiological information to provide an accurate profile of the tumor stage and the patients’ most likely future history.