◆ generally central (85-90%within a lobar or mainstem bronchi)and has a tendency to invade longitudinally along the bronchial wall,in a submucosal and intramural fashion Internal necrosis is common,but cavitation is extremely rare the worst prognosis,despite typically good response to initial chemotherapy generally central (85-90% within a lobar or mainstem bronchi) and has a tendency to invade longitudinally along the bronchial wall, in a submucosal and intramural fashion  Internal necrosis is common, but cavitation is extremely rare  the worst prognosis, despite typically good response to initial chemotherapy