PMC6136464_01
(a)-(d) CT axial and coronal scans depicting an exophytic mass in the lower pole of the left kidney: (a, b) initial presentation showing a well-circumscribed, enhancing mass with two small discrete, low attenuation areas in the inferior portion. (c, d) Enlargement of the renal tumor to almost twice the size from prior examination with compression of calyces, increased heterogeneity, and enhancement at the peripheral and anterior aspects of the mass.
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fig1
Comparative radiologic images are provided (Figure 1); the top images are radiographs with a smaller tumor from 2 years ago, while the bottom radiographs are from the patient's recent CT with a larger tumor.
(a)-(d) Gross image and representative microscopic images: (a) Solid and cystic mass with a tan-brown cut surface involving the lower pole of the kidney. (b) Representative illustration from the dominant portion of the tumor, an eosinophilic variant of ChC containing relatively uniform cells with distinct borders and central nucleus. (c)-(d) A minor component of tumor with a tubulocystic morphology, marked cellular atypia, and hobnail nuclear features, in keeping with CDC, low, and high magnifications provided.
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fig2
The mass had a tan-brown multiloculated cut surface (Figure 2(a)). Vimentin was only positive in the higher-grade tumor component, morphologically and by immunoprofile consistent with collecting duct carcinoma (see Figures 2 and 3 for the H&E and staining images).
(a)-(d) Staining pattern of different tumor components: (a) positive intracellular staining with Hale colloidal iron in ChC. (b) CK7 stain highlighting both ChC and CDC components, at their emerging front. (c) While vimentin stain is negative in the ChC tumor cells, only highlighting vasculature, (d) it is diffusely positive in the CDC component.
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fig3
Vimentin was only positive in the higher-grade tumor component, morphologically and by immunoprofile consistent with collecting duct carcinoma (see Figures 2 and 3 for the H&E and staining images).
(a)-(d) Two different areas of tumor retrieved from the paraffin embedded sample and processed for EM: (a) Low magnification image depicting overall ultrastructural features of the peripheral tumor cells. These cells are round-ovoid and have a central nucleus, mitochondria and cytoplasmic microvesicles. (b) Higher magnification shows plasma membrane border separating two tumor cells (arrowheads), nucleus (n), abundant mitochondria (m), dense cytoplasmic vesicles (arrows), and patches of rough endoplasmic reticulum (rer). (c) Low magnification image of high grade tubulocystic tumor cells. The cells are epithelioid and have large, irregularly shaped nuclei. (d) Higher magnification shows cytoplasm with mitochondria (m), patches of rough endoplasmic reticulum (rer), irregularly shaped nucleus (n), microvillus studded apical plasma membrane (arrowheads), and junctional complex between the adjacent tumor cells (arrows).
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fig4
The tumor section represented by monotonous cells contained rounded cells with centrally located nucleus (Figure 4(a)). At higher magnification, their cytoplasm was found to be packed with mitochondria and prevalent electron dense microvesicles (Figure 4(b)). The central tubulocystic-appearing regions contained elongated epithelioid cells with large, irregularly shaped nuclei (Figure 4(c)). At higher magnification, the plasma membrane of these cells possessed abundant microvillar projections with junctional complexes joining adjacent cells (Figure 4(d)).