Diagnostic criteria for minimally invasive pulmonary adenocarcinoma:
(1) tumor size <= 3 cm
(2) solitary mass
(3) predominantly lepidic growth pattern
(4) invasive component <= 0.5 cm in greatest dimension
The diagnosis is excluded if the tumor:
(1) invades lymphatics, blood vessels, or pleura
(2) contains tumor necrosis
(3) spreads through the air spaces
The invasive components to be measured include any histologic subtype other than lepidic (acinar, papillary, micropapillary, colloid, enteric, fetal or mucinous).
The cell type usually is nonmucinous but rarely can be mucinous.
