PMC5148770_01
(A) CT of the abdomen with IV contrast demonstrating large right renal mass extending into the IVC. (B) MRI of abdomen with IV contrast demonstrating a multilobulated, encapsulated 9.5 x 18.5 x 21.5 cm heterogeneously enhancing right renal mass extending into the IVC as well as a contralateral 2.9 cm para-aortic lymph node.
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Computed Tomography (CT) scan revealed a 9.5 x 18.5 x 21.5 cm right renal mass with tumor extension to the level of the hepatic IVC associated with perihilar lymphadenopathy (Fig. 1A). MRI of the abdomen and pelvis confirmed no local invasion (Fig. 1B).
Histopathology from surgical specimen. (A) Sheets of neoplastic cells with solid to nested architecture and branching capillary vasculature. (B) Cells with clear to finely granular eosinophilic cytoplasm with occasional markedly atypical cells. (C) Areas of the tumor exhibit cytoplasmic fine brown pigment consistent with melanin. (D) Fontana-Masson stain highlights melanin pigment within tumor cells (Not pictured: Melanin pigment was removed by bleaching).
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Histologically (Fig. 2), the mass was composed of solid nests of epithelioid cells (Fig. 2A) containing clear and eosinophilic cytoplasm (Fig. 2B). There were also foci of cytoplasmic melanin granules (Fig. 2C) highlighted by Fontana-Masson staining (Fig. 2D).