Lung
scar carcinoma (SC) was first described by Friedrich in 1939 as a type of
lung cancer that originates around peripheral
scars in the lung.
Scarring in the lung can result from a variety of
infections,
injuries, and
lung diseases.
Scars can also be due to repeated episodes of
tumor necrosis and healing. SCs are typically found as subpleural
adenocarcinomas with retraction or puckering of the overlying pleura. They were considered a histologic curiosity that was promoted for decades until doubts about their existence were raised in the 1980s. Finding
type III collagen,
type V collagen, and myofibroblasts characteristic of
fibrosis in the
scars, finally reversed the original SC concept. The presence of
type III collagen and extracellular matrix suggested an ongoing fibrosing process secondary to host response to the
neoplasm. The high concentration of
type III collagen in SC indicates that the fibrous tissue is in an active immature state compared with noneuplastic fibrous tissue, which is mature and contains type I and
type V collagen. A recent cohort analysis of data from the PLCO (Prostate, Lung, Colorectal and
Ovarian) cancer screening trial demonstrated a correlation between the presence of
scar and the development of
carcinoma, but the causation of this association has to be determined by future studies. The role of
inflammation,
infections, and smoking in the development of
cancer is discussed in this article. Additional research is necessary to determine if lung
scarring detected by imaging requires clinical monitoring in the context of the development of
lung cancer when a defined set of risk factors is identified.