Assessment of cellular adequacy of fine needle aspiration biopsy for small solid renal tumors.

Objective: Our aim was to evaluate the performance of fine needle aspiration (FNA) as a method for obtaining cellular material for the tissue diagnosis of small solid renal tumours.

Methods: Fifty-five patients with a small solid renal tumour (4 cm or smaller) underwent a FNA biopsy under computed tomography guidance. Direct smears and rinse of needle with Cytolyt® were prepared. The cellular adequacy was divided into three groups: satisfactory cellular material, scant cellular material and noncellular material.

Results: Postoperative pathological diagnosis showed 35 clear cell carcinomas, 10 papillary carcinomas, four chromophobe carcinomas, four oncocytomas, one adenoma and one metastatic carcinoma. A total of 21 (38.2%) FNA biopsies belonged to noncellular group. For clear cell carcinomas, the cellularity of satisfactory cellular group, scant cellular group and noncellular group was, respectively, seven (20.0%), nine (25.7%) and 19 (54.3%). Of the 10 papillary carcinomas, nine (90%) and all four chromophobe carcinomas (100%) had satisfactory cellular materials. The percentages of noncellular group among clear cell carcinoma, papillary carcinoma and chromophobe carcinoma were significantly different (P = 0.0020). Fifteen tumours were 2 cm or smaller and 40 tumours were larger than 2 cm. No significant difference was found in the percentage of noncellular material for the tumours 2 cm or less (40.0%) and for the tumours larger than 2 cm (37.5%; P > 0.05).

Conclusions: The cellularity of FNA biopsy of small solid renal masses might correlate with the subtype of renal cancers. FNA biopsy was an effective method of tissue sampling for papillary and chromophobe renal carcinomas.