Primary Renal Carcinoid: Two Rare Cases at a Single Center

Abstract

Renal carcinoid tumors are exceedingly rare. These neuroendocrine masses are most frequently found in the gastrointestinal and respiratory tracts. A renal carcinoid tumor has only been documented in around 100 cases. In this article, we report two additional cases in female patients ages 53 and 63. Both tumors were found incidentally on computed tomography scans. Both women underwent radical nephrectomies. Neither has shown evidence of metastasis nor relapse to date; however, the 63-year-old woman was lost to follow-up. In conclusion, upon discovery of the asymptomatic renal mass, renal carcinoid should be a consideration in the differentiation, and if suspected, may be treated with radical nephrectomy as was done in our hospital.

Keywords: carcinoid syndrome; neuroendocrine tumor; primary renal carcinoid.

Figure 1. CT scan of the abdomen and pelvis without (A) and with (B) IV contrast with urogram demonstrating a 3.8-cm heterogeneously enhancing lesion of the left lower renal pole as designated by the arrow.

CT, computed tomography

Figure 2. Gross kidney from radical nephrectomy. Gross pathology specimen: 3.5 × 3 × 2-cm yellow-tan mass visualized in the lower pole involving both cortex and medulla as indicated by the arrow. Multiple sections revealed a soft-red, possibly necrotic, lesion in the tumor parenchyma and no renal sinus or vascular involvement.

Figure 3. Microscopic evaluation of excised tumor. Variable growth patterns were noted. The tumor cells are arranged as trabeculae, ribbons, or nests (A, B). Solid expansile growth was also noted in focal areas. The tumor cells are uniform with limited cytoplasm and the nuclei are round. Most tumor cells showed “salt and paper” nuclear chromatin (C). Mitotic figures were rare and no geographic necrosis was seen. Immunohistochemistry revealed that the tumor cells were positive for CD56 (3+), synaptophysin (2+), and containing numerous membrane-bound, electron-dense neuroendocrine granules (D).

Figure 4. CT scan of abdomen and pelvis. Non-contrast exam demonstrating (A, B) and contrast (C, D) 7-cm prominently solid but enhancing dorsal right mid renal lesion with no evidence of osseous, adrenal, or hepatic metastasis or renal venous invasion or retroperitoneal lymphadenopathy as demonstrated by the arrow.

Figure 5. Pathological analysis of the resected tumor. Microscopic evaluation: solid, nest, and sheeting growth of tumor cells were presented in a hyalinized collagenous stroma. The tumor cells were uniform and contain eosinophilic or optically clear cytoplasm with rare mitoses. No angiolymphatic invasion or sinus involvement was identified (A, B). The tumor cells showed a positive reaction for CD56 and synaptophysin in the immunohistochemical study (C) and membrane-bound, electron-dense neuroendocrine granules in ultrastructural examination (D).

Figure 6. Octreotide uptake scan. Octreotide scan (360-degree view): suspicious focus of abnormal activity in the right abdomen, likely the third portion of the duodenum, which may represent primary carcinoid tumor versus a metastatic lesion. Please note right kidney is surgically absent and the area of the left kidney enhances as octreotide is absorbed normally by native kidney cells.