Screening for occult nodal metastasis in localized carcinoma of the prostate.

Metastatic involvement of pelvic lymph nodes in carcinoma of the prostate alters the prognosis and treatment of this disease. Our goal was to determine if additional techniques, such as immunohistochemical staining, could detect occult microscopic metastatic nodal disease not seen with routine hematoxylin and eosin staining. We examined paraffin embedded lymph nodes from 43 patients with clinical stage A or B carcinoma of the prostate who were candidates for radical prostatectomy and who underwent modified pelvic lymph node dissection with frozen section hematoxylin and eosin staining. Immunohistochemical staining for prostate specific antigen and prostate specific acid phosphatase was performed on the lymph nodes. Monoclonal antibodies to cytokeratins were used to confirm the epithelial origin of the prostate cells. An average of 9 lymph nodes and 42 histological sections per patient were stained. Based on routine hematoxylin and eosin staining the pathological staging was stage A in 3, stage B in 20, stage C in 9 and stage D1 in 11 cases. There were 17 well, 16 moderately and 10 poorly differentiated carcinomas. In 31 of 32 patients with negative nodes no occult metastases could be identified. One patient with poorly differentiated stage C cancer demonstrated occult nodal deposits by prostate specific acid phosphatase and not by prostate specific antigen. In the 11 stage D1 cancer patients immunohistochemical staining confirmed all malignant deposits and additional metastatic lesions were detected in only 1 patient. Unlike other carcinomas, such as breast, in which immunohistochemical staining yields a 14 to 37% occult metastasis rate, these data suggest that occult nodal metastases are infrequently seen in carcinoma of the prostate.