small-cell lung cancer

Small-cell lung cancer, or SCLC, is the sprinter of lung cancers: it grows fast, spreads early, and often has already traveled beyond the lung by the time it is found. Under the microscope its cells are small and densely packed, and biologically it behaves more like a neuroendocrine tumor than the more common non-small-cell types.

SCLC is strongly tied to cigarette smoking; it is uncommon in people who have never smoked. It frequently starts centrally, near the large airways, and can quickly involve the mediastinal lymph nodes and distant sites such as the liver, bones, brain, and adrenal glands. Because of this tendency to spread, it is staged in a simpler two-step way — limited stage (confined to one side of the chest, treatable within a single radiation field) versus extensive stage.

The flip side of its rapid growth is that SCLC is initially quite sensitive to chemotherapy and radiation, so treatment often shrinks it dramatically at first. Unfortunately it also tends to relapse, and surgery plays only a small role except in rare very early cases. Immunotherapy added to chemotherapy has become a standard part of treatment for extensive disease.

An honest note: SCLC can also produce paraneoplastic syndromes — remote effects caused by hormones or antibodies made by the tumor — which sometimes appear before the cancer itself is diagnosed.