This is a prospective study of surgically resected samples and lymph nodes of lung cancer patients. For histopathologically positive lymph nodes from a complete resection, the investigators would like to analyse tumor tissue by allelotyping and comparing these results with those observed in the primary lung tumor to establish a cartography of molecular alteration in resected lung cancer. For non histopathologically positive lymph nodes, the investigators would like to research the presence (or not) of micrometastasis by allele-specific PCR (polymerase chain reaction).

Genetic: It is a prospective study during two years with three years for follow-up. No control group is recruited.

Inclusion Criteria:

• Patients with resectable non-small cell lung cancer (stage I to IIIA), with a complete resection of the tumor and paired lymph nodes.
• Informed consent is required.

Exclusion Criteria:

• Another cancer
• Chemotherapy before surgical treatment

Patients with resectable non-small cell lung cancer (stage I to IIIA), with a complete resection of the tumor and paired lymph nodes