Primary renal carcinoid tumor in a horseshoe kidney presenting with constipation: A case report

Figure 1 Computed tomography urography findings of primary renal carcinoid tumor within horseshoe kidney. A: Axial contrast-enhanced computed tomography (CT) image (nephrographic phase): Demonstrates a heterogeneous-density mass (orange arrow) within the left-sided moiety of the horseshoe kidney, with a central low-density necrotic area visible; B: Another axial CT slice shows mass boundary relative to fused renal parenchyma (orange arrow); C: Coronal reformatted computed tomography urography image shows tumor location adjacent to horseshoe-kidney renal isthmus (orange arrow); D: Three-dimensional volume-rendering reconstruction demonstrates horseshoe-kidney fused lower-pole anatomical configuration and spatial relationship of the mass.

Figure 2 Gross pathological specimen of resected primary renal carcinoid tumor. Gross specimen from laparoscopic radical nephrectomy (6 cm × 4.5 cm × 5 cm). A solid, soft neoplastic mass with focal intratumoral hemorrhage and central necrosis is present; residual normal renal parenchyma surrounds the tumor tissue. A centimeter scale bar is shown at the bottom of the photograph.

Figure 3 Immunohistochemical staining of primary renal carcinoid tumor (magnification ×200). A: Chromogranin-A staining: Focal positive cytoplasmic immunoreactivity within tumor cell nests; B: Synaptophysin staining: Diffuse strong cytoplasmic positive staining of neoplastic cells; C: Vimentin staining: Diffuse positive staining within tumor stroma and neoplastic cell population.