CA9 level in renal cyst fluid: a possible molecular diagnosis of malignant tumours.
OBJECTIVE
The preoperative differentiation of malignant renal cystic tumours from benign lesions is critical, and it remains a common diagnostic problem. The aim was to examine if the Carbonic anhydrase 9 (CA9) level in cyst fluid can provide a molecular diagnosis of malignant cyst.


RESULTS
Twenty-eight patients with a cystic renal mass were included. Fine-needle aspiration was performed to obtain the fluid. Postoperative pathology confirmed that there were 16 cystic renal cell carcinomas. Twelve benign cystic tumours were used as controls. One hundred microlitres of supernatant of cyst fluid was used to measure the CA9 protein level, which was measured by an enzyme-linked immunosorbent assay technique. CA9 was strongly detected and considered as positive in the cyst fluid of all 16 cystic malignant tumours (>1000 pg/ml), whereas its expression was negative in 11/12 benign cystic tumours (<300 pg/ml). The difference in percentages of positive CA9 between malignant and benign renal cystic tumours was significant (P < 0.001).


CONCLUSIONS
The fluid of malignant cystic renal tumours contains a high level of CA9 protein. The measurement of CA9 level in cyst fluid may be used as a molecular diagnosis for differentiation between malignant and benign renal cystic masses.
Li
Guorong
G
Department of Urology, North Hospital, CHU of Saint-Etienne, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France. grli2001@yahoo.fr
Feng
Gang
G
Cuilleron
Muriel
M
Zhao
An
A
Gentil-Perret
Anne
A
Cottier
Michèle
M
Genin
Christian
C
Tostain
Jacques
J
D000951:Antigens, Neoplasm / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D044963:Biopsy, Fine-Needle; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000378:metabolism*; D002292:Carcinoma, Renal Cell / Q000175:diagnosis / Q000201:enzymology; D020420:Cyst Fluid / Q000201:enzymology; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000201:enzymology*; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases