Spectrum of differentiation in pediatric epithelial tumors of kidney: report of two cases.

Two unusual presentations of childhood renal cell epithelial tumors including one whose unique clinical manifestation was polycythemia are described. One was a renal cell carcinoma which was so poorly differentiated that ancillary histopathologic techniques were necessary to arrive at the correct diagnosis. The other case represented the opposite extreme being so well-differentiated as to raise the differential diagnosis of renal cell carcinoma versus renal cell adenoma with blastemal areas. These case studies exemplify the practical role for specialized histopathologic techniques in diagnosing pediatric renal tumors, which may not be feasibly or even accurately categorized into known renal tumor types using routine diagnostic methods.