UNUSUAL IMMUNOSTAINING PATTERN OF CHROMOGRANIN IN NORMAL UROTHELIUM AND IN TRANSITIONAL-CELL NEOPLASMS

We report an unusual pattern of immunostaining for chromogranin A in 2 4 transitional cell carcinomas (TCC). Positive immunostaining was seen with chromogranin A antisera in 10 of 16 urinary bladder TCC, neither of 2 prostatic TCC, 3 of 3 ureteral TCC and 2 of 3 metastatic TCC. Th is staining was demonstrated within the cytoplasm of transitional cell s at ah levels of the neoplastic epithelium, including cells near the basement membrane and at the free surface (umbrella cells). In 5 of 7 cases there was also immoreactivity of the non-neoplastic urothelium. Immunostaining with neuron-specific enolase and synaptophysin was nega tive in all of these cases and no neuro-secretory granules were identi fied in 7 cases examined by electron microscopy. This pattern of immun ostaining is probably due to reactivity with chromogranins or certain chromogranin-like proteins in the transitional cells, particularly in the umbrella cells.