Seminal vesicle invasion by prostatic carcinoma is directly associated with tumor staging; verification is challenging when the tumor demonstrates cribriform or papillary growth patterns or there are back-to-back small-gland proliferations. P504S is overexpressed in prostatic carcinoma and high-grade prostatic intraepithelial neoplasia with cytoplasmic immunoreactivity. p63 has positive immunoreactivity in basal cell nuclei of benign prostatic glands. Many researchers use a combination of these antibodies and their different colors.
To evaluate the usefulness of a single-color P504S/p63 cocktail immunostain in verifying prostatic carcinoma within the seminal vesicle.
Sections from 57 radical prostatectomy specimens of pathologic stage pT3b that contain seminal vesicle with prostatic carcinoma involvement were immunostained with primary antibodies against prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) and a cocktail of antibodies against P504S and p63.
Prostatic carcinoma cells from all 57 cases were diffusely positive for P504S, PSA, and PAP with cytoplasmic staining and no p63 nuclear staining. Seminal vesicle epithelium from all 57 cases was negative for all 3 markers with distinct p63 nuclear staining of the basal cells. Benign prostatic tissue was positive for PSA and PAP, as well as for p63, but negative for P504S.
The P504S/p63 one-color cocktail is a practical and cost-effective stain to differentiate prostatic carcinoma that involves the seminal vesicle from seminal vesicle epithelium. It is superior to PSA or PAP when sections contain both seminal vesicle and benign glands because PSA and PAP cannot distinguish benign from malignant glands.