Table 3.

Comparison of lung cancers associated with sporadic and germline mutations of EGFR gene.

Feature	Sporadic	Germline
Frequency	Relatively common	Exceedingly rare
Lung cancer type	Mostly adenocarcinoma	Mostly adenocarcinoma
Ethnic preference	East Asian	*White
Gender preference	Female	Female
Smoking status	More frequent in never smokers	More frequent in never smokers
Field cancerization effects	Occasional	*Occasional
Presence of T790M	Rare at initial diagnosis	Present at initial diagnosis (by definition)
Presence of second activating EGFR mutation	Rare at initial diagnosis	Frequent at initial diagnosis.
Inheritance	Not applicable	Dominant
Penetrance	Not applicable	*May vary with smoke exposure
Response to TKIs	Frequent initial response	*Predicted to be resistant

^*Given the exceedingly rare prevalence of germline T790M mutations, several of the observations (indicated by astericks) are tentative and need confirmation by study of further cases.