PMC9366044_01
(A) Timeline of events. Patient progressed on first- and second-line RCC therapy. Patient was on third-line therapy at the time of ED presentation. Creatinine peaked at 3.83 mg/dl. Rituximab 1 g IV was administered on days 1 and 15 (blue arrow). (B) CT imaging on 1 December 2020 showed left superior mediastinal lymph node measuring 28 mm x 30 mm; CT imaging on 23 February 2021 showed a decreased size of left superior mediastinal lymph node measuring 14 mm x 13 mm. (C) Renal biopsy. (Top left) Periodic acid-Schiff (PAS) stain shows mildly prominent capillary walls and mesangial expansion. (Middle left) Diffuse granular capillary wall immunoglobulin G (IgG) deposits. (Bottom left) C3 capillary deposits that vary in abundance and intensity. (Right) Electron micrograph images reveal subendothelial electron dense deposit (green triangle) and subepithelial electron dense deposits (red arrows).
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He had previously progressed on a 4-month course of first-line therapy with pembrolizumab (ICI) plus axitinib (oral TKI), which was discontinued 6 months prior to presentation, and a 3-month course of second-line cabozantinib (oral TKI) monotherapy, which was discontinued 3 months prior to presentation (Figure 1A). A non-contrast CT scan confirmed colitis and, notably, decreased tumor size of his metastatic disease (Figure 1B). Rare segmental mesangial and subendothelial deposits were also present (Figure 1C).