Using the 2536 genes distinguishing NE from adenocarcinoma prostate tumors, we applied unsupervised hierarchical clustering to gene expression data from prostates of TRAMP mice of 18 wks of age (T18, n = 4) and from OPN−/− TRAMP mice of 15 (n = 5) or 18 (n = 9) wks of age (OPT15 and OPT18, respectively) all devoid of US-detectable lesions (Table S1 and Figure S3 describe samples and class comparisons). The gene discussed is SPP1; the disease is prostate neoplasm.