PMC6188733_01
Axial, contrast-enhanced CT demonstrates a centrally located lobulated mass invading the renal vein and extending into the lumen of the inferior vena cava.
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CT demonstrated a centrally located, 4 x 4 x 4.6 cm, lobulated mass invading the renal vein and extending into the lumen of the infrahepatic inferior vena cava (Figure 1). CT angiography of the chest showed no evidence of detectable pulmonary emboli and bone scan was negative for metastases.
Gross image of the intrarenal mass and an elongated pedicle extending into the lumen of the inferior vena cava. The mass is lobulated and partially cystic and the pedicle has a smooth border.
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Gross examination of the nephrectomy specimen demonstrated a centrally located tumor with no gross invasion of adjacent tissue but with the pedicle extending into the inferior vena cava (Figure 2).
Cystic and biphasic tumor with benign, spindle cell stroma, focally resembling ovarian stroma, arranged with increased density in pericystic areas. Epithelial lining of cystic spaces is composed of a monolayer with cuboidal, flattened, and, focally, a hobnail appearance. No morphologic features of dysplasia are identified. Hematoxylin and eosin original magnification: 300x.
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fig3
Microscopically, the tumor was well demarcated with an elongated pedicle bulging into the renal pelvis and renal vein and a biphasic morphology with spindle cell stroma and a benign epithelial monolayer lining the cystic spaces (Figure 3). The stromal component was composed of uniform spindle cells without cellular atypia, necrosis, or mitoses (Figure 3). Focally, the stroma was densely cellular, resembling ovarian stroma, but no areas of scarring or fibrosis resembling corpora albicantia of the ovary were identified (Figure 3). The cystic spaces were lined by a single layer of epithelium, which was cuboidal or flattened or, focally, had a hobnail appearance (Figure 3).
The spindle cell stroma diffusely positive for smooth muscle actin. Immunoperoxidase stain for smooth muscle actin; original magnification: 125x.
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The stromal cells were diffusely and uniformly positive for SMA (Figure 4) and desmin and, focally, for CD10, while stains for inhibin, CD34, WT-1, S-100, MART1, and HMB-45 were negative.
Epithelium lining of cystic spaces showing diffuse and strong positivity for CK7. Immnuoperoxidase stain for CK7; original magnification: 200x.
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The epithelial component was positive for CK7 (Figure 5), for PAX-8, and, focally, for CD10.
Tumor within the renal vein lumen with tumor pedicle seen on the right and vessel wall on the left. Hematoxylin and eosin original magnification: 300x.
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The pedicle appeared to be floating in the vascular lumen without attachment to, or invasion of, the vascular wall (Figure 6).