noun
pathologist
A medical specialist who studies the causes and effects of diseases, especially through laboratory examination of body tissue.
彼は病理学者として病院で働いている。
He works at a hospital as a pathologist.
病理学 is the field of pathology, while 病理学者 is a person who specializes in it.
Compound of 病理 (pathology) + 学者 (scholar, specialist).