PMC7783360_01
Computerized tomography scans before and after immunotherapy in Case #1 Initial CT scan showing large left sided renal mass in April of 2019 (A) compared to CT scan in March of 2020 (B) showing substantially decreased mass.
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Subsequent CT scan revealed a 7.7 x 4.2 x 4.9 cm complex left renal mass with left adrenal gland involvement and regional lymphadenopathy ( Figure 1A ). Following 12 doses of pembrolizumab, repeat CT scan ( Figure 1B ) showed further decrease in the left renal mass to 2.5 cm (68% reduction from baseline) along with resolution of several sub-centimeter pulmonary nodules and the previously seen hepatic lesions.
Representative pathologic images from Case #1 Hematoxylin and eosin (H&E) stained slides at low-power (A) and high-power (B) magnification showing extensive hyalinized fibrosis with scattered chronic inflammation and hemosiderin laden macrophages in the area of tumor regression. The fibrosis extends into the adjacent fibroadipose tissue (C). Chronic tubulointerstitial nephritis and globally sclerosed glomeruli are present in the adjacent residual benign renal parenchyma (D).
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In areas of tumor regression, there was diffuse necrotizing granulomatous inflammation with areas of variably sized geographic necrosis, cholesterol clefting, and focal calcification surrounded by foamy histiocytic collections ( Figure 2 ).
PMC7783360_02
Computerized tomography scans before and after immunotherapy in Case #2 Initial CT scan in July of 2018 showing large right renal mass (A) and pulmonary metastases (B) compared to CT scan in December of 2019 showing substantially decreased mass (C) and resolution of pulmonary metastases (D).
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CT scan revealing an 11 x 9.3 cm heterogeneously enhancing mass replacing the majority of the right kidney ( Figure 3A ). CT scan also showed associated inferior vena cava tumor thrombus, a T10 lytic lesion, and innumerable pulmonary nodules in the bilateral lung bases concerning for metastatic disease ( Figure 3B ). After 13 total doses of nivolumab, her renal mass measured 3.9 x 3.2 cm (65% decreased from baseline,  Figures 3C-D ), and she underwent right radical nephrectomy two weeks later in September of 2019.
Representative pathologic images from Case #2 H&E stained slides at low-power (A) and high-power (B) magnification showing a massive infiltration of chronic inflammatory cells and foamy macrophages in the area of tumor regression. Areas of tumor regression also showed necrotizing granulomatous inflammation (C). Chronic tubulointerstitial nephritis, globally sclerosed glomeruli, and hemosiderin laden macrophages are present in the adjacent residual benign renal parenchyma (D).
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Sections showed no residual tumor, indicating a complete pathologic response to therapy ( Figure 4 ).