title: Patients with renal cysts associated with renal cell carcinoma and the clinical implications of cyst puncture: a study of 223 cases.
abstract: OBJECTIVE
  To clarify the association between renal cysts and renal cell carcinoma (RCC), we analyzed patient demographics, types of cystic disease, and modes of cyst-tumor coexistence along with the results of cyst puncture.
  
  
  METHODS
  A total of 507 hospitals provided information regarding clinical experiences with RCC and cyst puncture over a 2-year period.
  
  
  RESULTS
  Renal cysts were identified by preoperative imaging in 223 (4%) of 5721 patients with RCC. Histologic examination revealed cystic RCC in 56 patients (25%) and RCC associated with cystic diseases in 167 (75%). Cystic disease included simple cysts in 72 patients (32%), acquired cystic disease of the kidney (ACDK) in 62 (28%), multilocular renal cysts in 20 (9%), polycystic kidney in 3 (1%), and unspecified or miscellaneous in 10. Cyst puncture performed in 47 (21%) of 223 patients demonstrated bloody fluid in 20 cases and nonbloody fluid in 27. Cytologic analysis of cystic fluid obtained from 37 patients revealed a malignancy in 5 (14%), accounting for 25% of the bloody and 4.8% of nonbloody specimens. Cytology failed to detect RCC in ACDK and multilocular cysts but was positive in cases of cystic RCC and solitary cysts. Four of 5 cytology-positive cases comprised those of tumor in cyst and cyst within tumor.
  
  
  CONCLUSIONS
  Simple cysts and ACDK accounted for 60% of the renal cysts associated with RCC. Cystic RCC was involved in 25% of cases. Positive cytology may be expected in select cases, including those with close cyst-tumor relationships and those involving bloody cyst fluid. However, negative cytology does not exclude RCC.
authors.affiliation: Department of Urology, National Defense Medical College, Saitama, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hayakawa
authors.forename: T
authors.initials: T
authors.lastname: Hatano
authors.forename: A
authors.initials: A
authors.lastname: Tsuji
authors.forename: F
authors.initials: F
authors.lastname: Nakajima
authors.forename: Y
authors.initials: Y
authors.lastname: Ogawa
mesh_terms: D002292:Carcinoma, Renal Cell / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D007680:Kidney Neoplasms / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D015995:Prevalence; D011677:Punctures