Five New Cases of Primary Renal Carcinoid Tumor: Case Reports and Literature Review.

Carcinoid tumors, a slow-growing NET, most commonly arise in the gastrointestinal tract (73.7%), followed by the bronchopulmonary system (25.1%), and least commonly in the genitourinary system (<1%). Primary carcinoid tumors of the kidney-with approximately 100 cases reported in the literature since the first described case in 1966-are thought to be so rare because neuroendocrine cells are not typically found in the renal parenchyma. Here we present a series of five cases at our institution with primary carcinoid tumors of the kidney followed by a literature review. In the literature we describe the diagnostic stains used to determine renal carcinoid tumors. We also describe why partial nephrectomies are the gold standard treatment in these cases, while radical nephrectomy can be used in certain circumstances. Limited research on treatment of metastasis of these tumors exists, but we summarize the results of existing treatments. Major prognostic factors and survival of patients with these tumors is described as well as the increased prevalence of this tumors in patients with horseshoe kidneys. This study presents five new cases of primary renal carcinoid tumors and a comprehensive review of the previously published cases. We are able to make limited prognostic predictions from currently published literature, but we will continue to learn from our patients' long-term courses to draw conclusions about biological behavior, treatment outcomes, and recurrence of rare disease.