1. Criterion 1: Presence of 1 of 3 histologically proven diagnoses: 1) Primary small cell carcinoma of the prostate, defined by classic histologic features such as small tumor cells with scanty cytoplasm, darkly stained nuclei with homogeneous chromatin pattern. The tumor cells do not form glandular structure but grow as solid sheets with frequent mitotic figures and necrosis; 2) Intermediate atypical carcinoma of the prostate, which has histologic features distinct from small cell carcinoma or adenocarcinoma. The tumor grows as solid sheets or vague glandular structures. The tumor cells have moderate amounts of cytoplasm and centrally located, round and regular nuclei with fine, granular and homogeneous chromatin. Mitosis and necrosis are absent; 3) mixed histology tumors of the prostate, containing both adenocarcinoma and neuroendocrine or small cell components.