It is characterized by its origin in large central airways and histological composition of sheets of small cells with scanty cytoplasm. Small cell carcinoma is a tumor of neuroendocrine origin and is very aggressive, metastazing early and often.
Smoking is a well demonstrated etiologic factor in the development of small cell tumors.
This is also consistent with the predilection for the central airways and the mucosal irritation caused by smoking. Many patients who are diagnosed with small cell lung cancer are symptomatic at presentation but have been symptomatic for less than three months. Small cell carcinoma causes a number of paraneoplastic syndromes. Small cell carcinoma is the most common type of cancer to cause clinical hormone syndromes. The symptoms of Cushing's syndrome are nonspecific and are often attributed to other factors.