Histologic Distribution for Lung Cancer

Most lung cancers are classified as non-small cell. Squamous cancer was the most common type in the mid 1900's but now adenocarcinoma is most common. Vaious theories have been proposed for the increase (go here).
Histologic classification of non-small cell lung cancer:

squamous cell (epidermoid) carcinoma
         spindle cell variant
adenocarcinoma
         acinar
         papillary
         bronchoalveolar
         solid tumor with mucin
large cell carcinoma
         giant cell
         clear cell
adenosquamous carcinoma
undifferentiated carcinoma

The current classification of subtypes of small cell lung cancer are

small cell carcinoma
mixed small cell/large cell carcinoma
combined small cell carcinoma (small cell lung cancer combined with neoplastic squamous and/or glandular components)