Cytologic characteristics of congenital mesoblastic nephroma in fine-needle aspiration cytology: a case report.

The cytologic features of congenital mesoblastic nephroma (CMN) as recognized in smears of fine-needle aspirated cytology (FNAC) are reported. These included spindle- and tadpole-shaped cells with round to oval nuclei having small nucleoli and a smooth contour. The cytoplasm of these cells was dense and homogeneously stained. The background was composed of mucoid fibrillar material. The findings appear to be different from other types of renal tumors in infancy and specific enough for this tumor to allow diagnosis by FNAC.