Primary renal carcinoid tumour with lung metastasis misdiagnosed as renal cell carcinoma.

A 58-year-old man with a history of metastatic renal cell carcinoma (RCC) diagnosed 10 years prior, status post right nephrectomy, presented for evaluation of pulmonary nodules. A year after the nephrectomy, he had undergone cutaneous metastasectomy in the right flank area, and a further 2 years later he had had his second cutaneous metastasectomy in the right chest wall. Both cutaneous pathologies had, at the time, shown metastatic neoplasm with histological features compatible with those of the previous renal tumour. He was treated with sorafenib. 3 years later he developed asymptomatic pulmonary nodules, which gradually doubled in size over the next 2.5 years. He underwent bronchoscopy and left lower lobe biopsy. Pathology revealed a metastatic renal carcinoid/neuroendocrine tumour. Second review of the previous renal neoplasm and the cutaneous metastatic pathology showed trabecular architecture, consistent with carcinoid, but mimicking the long parallel arrays that have been described in some cases of papillary RCC.