PTEN mutations occur at a low frequency in NSCLC and in small-cell lung cancer (SCLC), with the notable exception of squamous cell carcinoma of the lung, in which PTEN is mutated in 6–9% of the cases and significantly altered in up to 15% of cases, taking into account loss of expression as well (72). The gene discussed is PTEN; the disease is non-small cell lung carcinoma.