Major histologic patterns of invasive adenocarcinoma

(A) Lepidic predominant pattern with mostly lepidic growth (right) and a smaller area of invasive acinar adenocarcinoma (left).
(B) Lepidic pattern consists of a proliferation type II pneumocytes and Clara cells along the surface alveolar walls.
(C) Area of invasive acinar adenocarcinoma (same tumor as in A and B).
(D) Acinar adenocarcinoma consists of round to oval-shaped malignant glands invading a fibrous stroma.
(E) Papillary adenocarcinoma consists of malignant cuboidal to columnar tumor cells growing on the surface of fibrovascular cores.
(F) Micropapillary adenocarcinoma consists of small papillary clusters of glandular cells growing within this airspace, most of which do not show fibrovascular cores.
(G) Solid adenocarcinoma with mucin consisting of sheets of tumor cells with abundant cytoplasm and mostly vesicular nuclei with several conspicuous nucleoli. No acinar, papillary, or lepidic patterns are seen, but multiple cells have intracytoplasmic basophilic globules that suggest intracytoplasmic mucin.
(H) Solid adenocarcinoma with mucin. Numerous intracytoplasmic droplets of mucin are highlighted with this diastase-periodic acid Schiff stain.