Small cell carcinoma of the lung is one of the two high-grade neuroendocrine carcinomas of the lung (the other one being large cell neuroendocrine carcinoma). It accounts for 10-15% of all primary lung carcinomas. The classical presentation is that of an elderly patient, heavy smoker or ex-smoker, with a central mass spreading along the bronchial tree with hilar and/or mediastinal lymphadenopathy. In addition, patients may present with a variety of paraneoplastic syndromes such as SIADH (syndrome of inappropriate secretion of antidiuretic hormone, Cushing's syndrome (due to ACTH production) and Eaton-Lambert syndrome among many others.

Histologically, the tumor is composed of sheets of small (roughly 2-4X the diameter of a resting lymphocyte) round to oval cells with scant cytoplasm, high N/C ratio, finely granular chromatin with inconspicuous nucleoli. Nuclear molding and crush artifact are prominent features, as are numerous mitoses and apoptotic debris. Necrosis is frequently widespread. A characteristic feature of small cell carcinoma is the so-called Azzopardi effect: the coating of blood vessels by basophilic DNA debris. To date, no preinvasive/preneoplastic lesions are identified for small cell carcinoma (and large cell neuroendocrine carcinoma).

Immunohistochemically, the cells are positive for pancytokeratin (AE1/AE3) in a dot-like or paranuclear pattern. The neuroendrine markers such as synaptophysin, chromogranin and CD56 are typically positive with CD56 being the most sensitive and chromogranin the least sensitive stains. TTF-1 is positive in the majority of cases. The ki-67 proliferation index typically averages ≥ 80%.

Treatment is generally nonsurgical and includes chemoradiation as well as prophylactic cranial irradiation. The prognosis is poor with a two-year survival rate of less than 10%.