[Pathologic diagnosis and differential diagnosis of small cell neuroendocrine carcinoma of kidney].

OBJECTIVE

To study the clinicopathologic features and histologic differential diagnosis of small cell neuroendocrine carcinoma (SmCC) of kidney.

METHODS

The clinicopathologic features of 12 cases of SmCC of kidney encountered during the period from 1999 to 2010 were retrospectively reviewed.

RESULTS

Six cases of primary and 6 cases of metastatic SmCC involving kidney were identified. Amongst the primary renal SmCC, 2 were located in renal parenchyma and 4 in renal pelvis. Chest X-ray showed negative findings. Five of them underwent radical nephrectomy. On gross examination, the tumor was located centrally around the renal pelvis in 4 cases and peripherally in renal parenchyma in 1 case. On the other hand, 4 of the 6 cases of metastatic SmCC were discovered during therapy for pulmonary SmCC. Two of these patients presented with abdominal pain and gross hematuria, with lung and renal tumor masses identified simultaneously. The diagnosis of all the 6 cases of metastatic SmCC was confirmed by fine needle aspiration biopsy. Microscopically, pure SmCC was demonstrated in the 2 cases of primary renal parenchymal SmCC and 6 cases of metastatic SmCC. The 4 primary renal pelvic SmCC coexisted with urothelial carcinoma component. On immunohistochemical study, all cases were positive for cytokeratin, synaptophysin and CD56. All metastatic cases and 4 primary cases were also positive for TTF-1. Of six patients with primary SmCC two died 4 and 9 months after operation, and two were alive with a follow-up of 25 and 138 months, respectively. Five of six cases with metastatic SmCC died 3 - 8 months after diagnosis. The other 3 cases were failed to follow-up.

CONCLUSIONS

Both primary and metastatic SmCC can be found in the kidney. Although rare, primary SmCC is located either in renal parenchyma or in pelvis. The diagnosis of SmCC relies on morphologic examination and immunohistochemical study. TTF-1 immunostaining cannot reliably distinguish primary from metastatic SmCC in kidney. Correlation with clinicoradiologic findings and demonstration of coexisting urothelial carcinoma component (if any) is helpful in delineation of the tumor origin.