noun, noun which may take the genitive case particle 'no'
Medical term for a localized area of disease, such as a tumor, infection, or abnormal tissue. Used both as a noun and adjectivally with の.
CT検査で肺に小さな病巣が見つかった。
A small lesion was found in the lung on the CT scan.
この薬は病巣に直接
This medicine acts directly on the focus of the disease.