PTEN and neuroendocrine neoplasm: The functional activation of the PI3K/Akt pathway has been investigated in the spectrum of pulmonary or other neuroendocrine tumours only by the indirect evidence of the expression of functionally related molecules, such as PTEN (22), tuberous sclerosis complex (TSC) (23) and mammalian target of rapamycin (mTOR) (24,25).