How is small cell lung cancer (SCLC) classified?

Updated: Sep 12, 2019
  • Author: Abid Irshad, MD; Chief Editor: Eugene C Lin, MD  more...
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Historically, the histologic identification of small cell cancer dates back to the 1920s, when the small cell/oat cell tumor was shown to be a carcinoma of the lung and not an oat cell sarcoma of the mediastinum, as thought earlier. This cancer was also noted to occur in patients younger (27-66 yr) than those with the other cancers.

Since that time, many histologic subtypes of SCLC have been found, and attempts have been made to classify this tumor. However, disagreement regarding the classifications still exists. In 1998, the International Association for the Study of Lung Cancer (IASLC) classified SCLC into 3 general histologic subtypes: small, mixed, and combined. According to this classification, the small-cell subtype includes the previous World Health Organization (WHO) variety of oat cell and intermediate types. The mixed variety encompasses mixed cell and large cell cancers. (In the WHO classification, this is considered a combined variety.) The combined variety includes a significant proportion of squamous cell or adenocarcinoma cell cancers in addition to small cell cancers (1-3% of cases of SCLC). [14]

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