Malignant rhabdoid tumor of the kidney diagnosed by fine-needle aspiration cytology.

A case of malignant rhabdoid tumor (MRT) of the kidney diagnosed by fine-needle aspiration cytology (FNAC) in a 4-mo-old infant who later developed a left pleural effusion (also recognized as metastatic disease by cytologic means) is reported. Rhabdoid cells--intermediate-sized cells with vesicular nuclei and prominent nucleoli, exhibiting a paranuclear, eosinophilic, dense inclusion--seem to be specific enough for this tumor to allow diagnosis by FNAC.