case_images: PMC11694286_01
case_images: (a) MRI of the right renal mass with IVC thrombus on presentation and (b) CT of the chest showing lung metastasis on presentation.
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case_images: Subsequent magnetic resonance imaging (MRI) of the abdomen showed a heterogeneously enhancing 11.4 x 12.2 x 13 cm mass compatible with RCC in the upper pole of the right kidney with extensive venous invasion (Figure 1(a)). Several subcentimeter para-aortic lymph nodes and three indeterminate subcentimeter arterially enhancing liver lesions were also observed (Figure 1(b)).
case_images: Core biopsy of the lung right middle lobe. Cores contained focal malignant cells with clear cytoplasm (*) which showed cytologic architecture consistent with carcinoma (a, 4x; b, 20x). Immunohistochemical staining revealed the clear cells were positive for PAX8 (c) and carbonic anhydrase (CAIX) (d). This immunophenotype is characteristic of RCC.
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case_images: A right middle lobe lung core biopsy showed malignant cells with clear cytoplasm morphologically consistent with carcinoma (Figure 2(a) and (b)). The malignant cells stained positive for PAX8 (Figure 2(c)), supporting renal origin, and carbonic anhydrase IX (CAIX) (Figure 2(d)) an immunophenotype which is most consistent with clear cell type RCC.
case_images: CT after pembrolizumab plus axitinib showing shrinking of right upper pole renal lesion with persistent invasion into the left renal vein and infrahepatic IVC.
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case_images: After 26 months of systemic treatment, CT of the right upper pole renal mass had shrunk to 6.2 cm x 4.5 cm with persistent invasion into the left renal vein and infrahepatic IVC (Figure 3).
case_images: Inferior vena cava with focal atypical cells with clear cytoplasm suspicious for residual clear cell RCC (a, 4x; b, 20x). The atypical cells showed negative staining for pan-cytokeratin (c, 20x) and PAX8 (d, 20x), consistent with macrophages rather than residual RCC.
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case_images: The renal mass showed extensive treatment effect with abundant, dense fibrosis, hemorrhage, and hemosiderin deposition (ypT0) (Figure 4(a)). IVC, focal suspicious cells with clear cytoplasm were identified admixed with fibrosis (Figure 4(b)). Immunohistochemistry was used to further characterize these cells, which demonstrated negativity for pan-cytokeratin (Figure 4(c)) and PAX8 (Figure 4(d)), confirming they represented macrophages rather than residual tumor.