CLUSTERED P53 IMMUNOSTAINING - A NOVEL PATTERN ASSOCIATED WITH PROSTATE-CANCER PROGRESSION

Abnormal p53 protein accumulation is typically defined as present when greater than 5 or 10% of cancer cells stain positively, We present a novel approach whereby immunopositivity is defined when 15 or more cel ls within a 300 x 400-mu m(2) field exhibit p53 protein accumulation; a feature that we have called ''clustered'' staining, We assessed p53 immunostaining of moderately differentiated, clinically localized pros tate cancers derived from two patient groups: those without cancer rec urrence 5 years after radical prostatectomy, and those in whom cancer had recurred following radical prostatectomy, Clustered p53 immunoposi tivity was present in 10 (63%) of 16 patients in the recurrent group a nd in only 7 (21%) of 33 in the nonrecurrent group, Clustered p53 stai ning was clearly associated with cancer recurrence (P < 0.01). This re finement of a commonly used assay may help define the biological aggre ssiveness of a cancer.