Composite epithelial kidney tumor comprising of adeno and neuroendocrine carcinomatous components: an unusual variant of renal cell carcinoma.

Renal cell carcinomas accounts for an approximately 2% of human malignancies with at least ten different histological subtypes recognized by the World Health Organization (WHO) 2004 classification. Composite carcinomas with dual divergent epithelial differentiation in kidneys are extremely uncommon. We report an unusual case of a 37-year-old female who presented with symptoms related to renal tumor for the last three years. Computed tomography scan revealed a large heterogeneously contrast enhancing left kidney mass comprising of two distinct histological components of low grade adenocarcinomatous and carcinoid-like low grade neuroendocrine carcinomas with presence of hilar lymph nodal metastases of both the components. The component of adenocarcinoma was immunoreactive to E-cadherin, cytokeratins 7 and 19 with negativity for cluster of differentiation 10, cytokeratin 20, CD117, and vimentin; while the neuroendocrine component was immunoreactive for vimentin, chromogranin and synaptophysin with negativity for CD10, CD117, and cytokeratins 7, 19 and 20. MIB-1 labeling index in the both the components was 2-3%. The present case is the first of its kind to be reported in the kidney and emphasizes the diversity potential of kidney tumors.