Clinical significance of "cannibalism" in urinary cytology of bladder cancer

OBJECTIVE: To investigate the cytologic characteristics and clinical significance of "cannibalism" (cytophagocytosis), a characteristic histologic finding associated with malignancy,found in urinary cytology samples during the diagnosis of bladder cancer. STUDY DESIGN: The subjects were 252 patients with bladder cancer initially treated from 1981 to 1991. For their pretreatment urine samples, membrane filtration was performed to determine the presence and amount of cannibalism, a tumor cell within a tumor cell. The urinary cytologic findings were then correlated with the histologic findings of primary bladder cancer. RESULTS: Only cells from urinary cytology-positive specimens demonstrated cannibalism The positive rate of cannibalism was significantly higher in grade 3 (25%) than grade 1 (0%) or 2 (8%) superficial papillary cancer (P<.01) and also higher in muscle-invading bladder cancer (57%) than grade 3 superficial papillary cancer (P<.01). The rate did not differ significantly between muscle-invading cancer and superficial nonpapillary cancer (44%). In 198 patients with superficial bladder cancer, progression was observed in 19 (10%) during a mean follow-up of 72 months. All of them showed positive urinary cytology results in pretreatment samples, and among the patients with positive urinary cytology, the progression rate was significantly higher when cannibalism was present than when it was absent (38% vs. 17%, P <.05). Moreover, in high grade cases, cannibalism had significant predictive value for progression By multivariate analysis, cannibalism was an independent factor for prediction of progression, as were tumor grade and stage. CONCLUSION: Cannibalism in urinary cytology appears to be an indicator of both the anaplastic grade and invasiveness of transitional cell carcinoma of the bladder. Furthermore, cannibalism may provide a reliable predictor of progression of superficial bladder cancer.