Composite renal cell carcinoma with clear cell renal cell carcinomatous and carcinoid tumoral elements: a first case report.

Renal endocrine tumours are extremely rare, and carcinoid tumoral elements in renal cell carcinoma have never been reported. This is the first report of a composite renal cell carcinoma containing a clear cell renal cell carcinoma associated with carcinoid tumoral elements, in a patient with synchronous metastatic disease. In the absence of specific radiological and clinical manifestations, typical morphological features as well as an immunostaining profile of neuroendocrine differentiation were identified by microscopy. Secondary nodal and liver localisations were characterised by carcinoid elements only. Despite antiangiogenic therapy, liver metastasis progressed, suggesting that adjuvant therapy cannot be based on the presence of the clear cell renal cell carcinoma component. In this context, extensive tissue sampling is recommended to reveal the endocrine component that is the most aggressive element of such a composite carcinoma.