Cytologic characteristics of clear-cell sarcoma of the kidney (CCSK) in fine-needle aspiration biopsy (FNAB): a report of 4 cases.

The cytologic findings observed in fine-needle aspiration biopsy (FNAB) of four cases of clear-cell sarcoma of the kidney (CCSK) are reported. Smears contained a monomorphic population of cells exhibiting non-descriptive cytoplasm and almost nude round to oval nuclei with smooth contour, evenly dispersed fine chromatin granules, and one or two small nucleoli. Some nuclei (approximately 40%) had a bar resulting from grooving or folding of the nuclear membrane. Comparison with smears of classical Wilms' tumor and malignant rhabdoid tumor allowed to recognize a distinctive pattern, different from other tumors of the kidney in infancy. The recognition of the CCSK cytologic pattern justifies the usage of aggressive preoperative chemotherapy protocols or the indication of surgery avoiding delays.