Mills Ch35 Prostate

976

SECTION IX : GenitourinaryTract

all the cytoplasmic vacuolar partitions and shows no evidence of protein within the vacuoles. Darker H&E staining not only darkens the partitions but also enhances diffuse staining throughout the cytoplasm, which obscures both the clear cell appearance and the visualization of the vacuoles. The secretory lining of peripheral zone glands conveys an orderly appearance, with a single layer of columnar cells having basally oriented nuclei. In most glands, however, the epithelial row shows considerable random variation between neighbor- ing cells in the ratio of cell height to width and in apparent cell volume. Nuclear location also varies from the basal cell aspect to the mid-portion of the cell. The luminal cell border is con- sequently often uneven, and its irregularity is accentuated by frequent cells whose luminal aspect appears frayed. Central zone epithelium shows an accentuation of the mild disorder of cell arrangement of the peripheral zone/ transition zone (Figs. 35.23 and 35.27). Here the epithe- lium is variably thickened by prominent cell crowding. Nuclei, which are usually larger than in the peripheral zone, are often displaced further from the cell base than in the peripheral zone and appear pseudostratified. The dark cytoplasm, thickened variable epithelium, and complex architecture in the central zone may be misinter- preted as PIN on needle biopsies. However, the distinctive histologic features coupled with the absence of enlarged nuclei, nucleoli, or hyperchromasia and an often prominent basal cell layer are useful in excluding this diagnosis. DEVIATIONS FROM NORMAL HISTOLOGY Beyond the age of 30 years, many prostates begin to show a variety of deviations from normal morphology (3,6,32,33). Their prevalence and extent of these changes progressively increase with age so that most prostates are quite heteroge- neous in histologic composition by the seventh decade of life. Although these histologic patterns seldom have clini- cal significance, their distinction from adenocarcinoma is sometimes difficult. Early morphologic studies concluded that focal atrophy in the prostate was a manifestation of aging and was seen as early as 40 years of age. In fact, focal atrophy in the prostate is often the consequence of previous inflammation rather than aging (3,6). The number and extent of atrophic foci tend to be greater in older men, but their histologic appearance is identi- cal to that of isolated foci found as early as 30 years of age. Atrophy is an extremely common lesion and is mainly seen in the peripheral zone, where its distribution is typically segmental along the ramifications of a duct branch (3,6). Publication of a Working Group classification (43) has high- lighted four patterns of focal atrophy with distinctive histo- logic features. The most common of these is termed simple atrophy , in which irregular or angulated, basophilic acini are seen at low magnification. Some degree of acinar dropout may be present. Individual acini have reduced cytoplasm,

FIGURE 35.29  Simple atrophy demonstrating angulated, basophilic glands with limited to no cytoplasm and dark nuclei; scattered chronic inflammatory cells are also present.

yet nuclei often retain their usual size (Fig. 35.29). Simple atrophy is commonly associated with chronic inflammation that may involve the prostatic stroma or epithelium. Espe- cially in the setting of inflammation, atrophic glands may exhibit small nucleoli. The combination of small angulated glands with variable architectural distortion and nucleoli may mimic cancer and cause diagnostic difficulty. Simple atrophy with cyst formation is characterized by rounded acini of very large diameter which have a sieve-like gross and cyst-like microscopic appearance. Glands show back to back architecture with little intervening stroma (Fig. 35.30). Cytologically, the cyst-like acini have little to no apparent cytoplasm and unlike simple atrophy , are uncommonly associated with chronic inflammation. Postatrophic hyperplasia , like simple atrophy , has a baso- philic appearance at low magnification and is composed of small round acini in a vaguely lobular arrangement. In radical

FIGURE 35.30  Back-to-back large caliber rounded acini with little to no cytoplasm characteristic of cystic atrophy.