Atypical hyperplasia and latent carcinoma of the prostate from 310 prostates of all age obtained at autopsy were studied. Atypical hyperplasia was graded into 3 groups based on the frequency of nucleoli and cell arrangement. The results were as follows: the origin of both atypical hyperplasia and latent carcinoma was considered to be in the peripheral zone. The frequency of atypical hyperplasia increased with age. Atypical hyperplasia was found in younger generation than latent carcinoma. Grade

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... of atypical hyperplasia increased with age. Atypical hyperplasia was often coincident with latent carcinoma: 74% of atypical hyperplasia were associated with latent carcinoma. Atypical hyperplasia was significantly associated with multicentric latent carcinoma. All these findings supported the assumption that atypical hyperplasia was a premalignant lesion. Clinically, in a case in which atypical hyperplasia is found in biopsy, intense follow-up will be necessary. In particular, in cases of grade 3 atypical hyperplasia, further study for detection of probable coexistent carcinoma is recommended.