Who is referred to as a pathologist?

A pathologist is defined as a medical professional who specializes in the study of diseases. This field encompasses understanding the nature, causes, progression, and effects of various diseases through examination and analysis of tissues, cells, and bodily fluids. By studying these elements, pathologists can provide critical insights into diagnoses, guide treatment plans, and conduct research on disease mechanisms.

While other roles mentioned in the options may intersect with a pathologist's work, such as a medical doctor who treats patients or an oncologist who diagnoses cancers, these roles involve applying clinical knowledge rather than solely studying the disease processes. A pathologist's primary function is rooted in the investigation and understanding of diseases from a laboratory perspective, making option B the most accurate representation of their role.