Chemopreventive Target for Prostate Cancer: Prostatic Intraepithelial Neoplasia

Prostatic intraepithelial neoplasiaJohn McNeal introduced the term intraductal dysplasia of the prostate in the early 1960s, postulating that carcinoma of the prostate arose from active ductal/acinar epithelium and not from atrophic acini (McNeal, 1965(McNeal, , 1988;;Amin et al., 1993).Later various terms have been rasied such as large acinar atypical hyperplasia with malignant change (Allam et al., 1996) and ductacinar dysplasia (McNeal, 1988).None of these have gained popularity.The term Prostatic intraepithelial neoplasia (PIN) was first proposed by Bostwick and Brawer in 1987, and this term was accepted at the 1989 Workshop on Prostatic Dysplasia (Bethesda, Md; March 1989) as the preferred nomenclature for this preneoplastic change (Bethesda, Md;March 1989;Drago et al., 1989).PIN refers to the putative precancerous end of the continuum of cellular proliferations within the lining of prostatic ducts, ductules and acini (Bostwick and Amin, 1996;Bostwick and Qian, 2004).PIN is the most likely precursor of prostate cancer and has been described as a premalignant or pre-invasive form of prostate cancer (Sakr et al., 1993;Bostwick, 1996).Although two histopathologic lesions in the prostate were proposed as being premalignant (PIN and atypical adenomatous hyperplasia, AAH), there is less evidence of a premalignant role for AAH than there is for PIN (De La Torre et al., 1993;Jones and Young, 1994;Epstein, 1994;Bostwick, 1996).Within these lesions, studies have identified impaired and abnormal www.intechopen.comIntraepithelial Neoplasia 180 differentiation, increased proliferation, and abnormal DNA content and elevated ras protooncogene mRNA expression (Jones and Young, 1994).There are two grades of PIN (low-grade and high-grade), although the term PIN is usually used to indicate high-grade PIN (HGPIN).The high level of interobserver variability with low-grade PIN (LGPIN) limits its clinical utility, and many pathologists do not report this finding except in research studies.Low grade PIN (LGPIN) is only a very early precursor, and might even not be considered as a precancerous lesion.Moreover, the distinction between LGPIN and normal epithelium might be observer related (