Figure 16d. Squamous cell carcinoma with ipsilateral hilar lymph node metastasis in a 75-year-old man. (a) Transaxial CT scan (2.5-mm collimation, mediastinal window) obtained at the level of the left atrium shows an 18-mm nodule in the right lower lobe (bottom arrowhead), along with ipsilateral hilar lymph node enlargement (top arrowhead). (b) Low-power photomicrograph (original magnification, x40; avidin-biotin complex method) obtained after immunostaining for VEGF shows strong cytoplasmic positive staining (arrows). (c) High-power photomicrograph (original magnification, x100; avidin-biotin complex method) obtained after immunostaining for microvessel density with CD 31 shows numerous stromal microvessels (arrows). (d) Serial CT scans obtained at 30-second intervals at similar levels after power injection of 120 mL of 30% iodinated contrast material (injection rate, 3 mL/sec) allow a dynamic enhancement study of the nodule. Peak attenuation of the nodule was 121 HU, net enhancement (peak minus precontrast attenuation) was 68 HU, and time to peak enhancement was 60 seconds (very strong and rapid enhancement). Scale at left is in Hounsfield units.