Figure 10c. Pulmonary tumor thrombotic microangiopathy caused by metastatic gastric carcinoma in a 57-year-old man. (a) Thin-section (1.5-mm collimation) CT scan obtained at the level of the left basal trunk shows multifocal tree-in-bud appearances (arrows) caused by tumor emboli. (b) Photograph of the autopsy specimen shows accentuated and enlarged centrilobular axial interstitium in the peripheral lung (arrows), a finding that corresponds to the tree-in-bud appearance seen at CT. (c) Photomicrograph (original magnification, x40; H-E stain) of an arteriole shows small nests of tumor cells (arrows). The vessel lumen is occluded mainly by lamellated fibrointimal proliferation that surrounds the tumor cell nests.