PMC4276681_01
Well-demarcated but not encapsulated tumor with focal involvement of the adjacent alveolar air spaces (hematoxylin-eosin, original magnification x100).
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Microscopically, at low magnification, the tumors were unencapsulated (Figures 1(a) and 1(b)) but well circumscribed (Figure 1(a)) with a few solid tumor nests noted in the alveolar air spaces at the periphery of each lesion (Figure 1(b)).
Variable histological features: prominent capillary network (a), pleomorphic nuclei (b and c), solid tumor nodules (c), and small cytoplasmic lipid vacuoles (d) (hematoxylin-eosin, original magnification x200 (a)-(c), x400 (d)).
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Both tumors contained a prominent capillary network (Figures 2(a) and 2(b)) with intervening stromal cells exhibiting varying degrees of pleomorphism (Figures 2(b) and 2(c)). The cytoplasm of the stromal cells was eosinophilic to clear (Figures 2(b) and 2(c)) and many contained fine lipid vacuoles (Figure 2(d)). Occasional solid tumor lobules devoid of vasculature were also present, often associated with more cytological atypia (Figure 2(c)). Despite being highly vascular, the smaller (0.7 cm) tumor nodule showed primarily bland cytological features in the stromal cells as depicted in Figure 2(a).
Positive immunoreactivity is characteristic of hemangioblastoma with the following markers: (a) inhibin-A, (b) neuron specific enolase (NSE), (c) S-100, and (d) CD34 (original magnifications for all images: x400).
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Immunostains for CD34 were positive in the prominent capillary vasculature, but not in the stromal cells (Figure 3).
Histologic features on frozen sections of the lung mass from the right lower lobe: microcystic and vascular architecture and nuclear pleomorphism mimicking metastatic renal cell carcinoma (hematoxylin-eosin, original magnification x400).
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