It’s difficult to put a number or some sort of growth curve to small cell lung cancer (SCLC) or any disease simply because for every patient, the growth rate to be measured is from diagnosis forward, and because the speed with which SCLC spreads will be dictated in part by the health and age of the patient. That said there are two important growth patterns that differentiate small cell lung cancer from the non-small cell types of lung cancer. The growth rates for non-small cell lung cancer also vary based on type of cell; there are several varieties of malignant cell that can define non-small cell lung cancer. But SCLC is believed to be more aggressive than all of them.
Small cell lung cancer has as its identifying malignancy a small, oval shaped cell referred to as an oat cell. Sometimes the disease is called oat call cancer. SCLC can also have other type(s) of cancer cells, one or more of the non-small cell variety. When there is more than one type of cell present the disease is called mixed SCLC but is still identified as small cell cancer and still exhibits the growth characteristics associated with the oat cell.
Oat cells multiply rapidly. They are very small and unlike most other cells contain little cytoplasm, the gel-like material that holds all of the cell components except the nucleus. An oat cell can look like it’s all nucleus under the microscope. These cells multiply rapidly and can create a tumor of substantial size under some circumstances; however one Russian study indicated that growth of the principal tumor occurred at a moderate rate. Some forms of lung cancer are tenacious and hard to treat, but may grow by creating two or more smaller malignant nodes rather than a single large tumor. SCLC is more likely to create a single tumor, but it may not be noticed or create symptoms until the disease has spread to other areas.
Early Spread to Other Areas of the Body
Perhaps the most important factor that makes SCLC substantially different from other lung cancer types is its tendency to metastasize to other parts of the body early in the development phase of the disease. Usually cancers will grow in a localized area, into a tumor increasing in size or spreading over adjoining tissue. After the disease has matured and is generating large numbers of malignant cells it will travel to distant parts of the body through the lymph system, blood vessels, or some other means.
Small cell lung cancer doesn’t follow this pattern. It metastasizes very early in the development of the disease, leading to the presence of malignant cells in locations well removed from the lung where the tumor initially formed. This metastasis happens so early in the process that it may have already occurred by the time the patient begins to exhibit the symptoms associated with lung cancer: a persistent cough, chest pain, coughing up blood, etc. The growth rate to other parts of the body is rapid and more importantly, occurs early in the development of the disease. Over two thirds of all SCLC cases have spread to other areas of the body before they are diagnosed.