Stage I includes: (T1a-c, N0, M0, PSA less than 10, Gleason equal or less than 6); (T2a, N0, M0, PSA less than 10, Gleason equal or less than 6); (T1-2a, N0, M0, PSA X, Gleason X). T1a: Tumor incidental histologic finding in 5% or less of tissue resected. T1b: Tumor incidental histologic finding in more than 5% of tissue resected. T1c: Tumor identified by needle biopsy (e.g., because of elevated PSA). T2a: Tumor involves one-half of one lobe or less. cN0: No regional lymph node metastasis. pN0: No positive regional nodes. M0: No distant metastasis. Gleason Equal or Less than 6: Well differentiated (slight anaplasia). Gleason X: Gleason score cannot be processed. (AJCC 7th ed.) [from NCI]