Mills Ch35 Prostate

978

SECTION IX : GenitourinaryTract

FIGURE 35.36  Prominent squamous metaplasia is often present sur- rounding areas of ischemia or frank infarct.

FIGURE 35.35  Focus of basal cell hyperplasia showing multiple layers of rounded basal cells with a central flattened layer of eosinophilic secretory cells. The basal cells commonly contain small prominent nucleoli.

Grossly BPH is usually recognized as a globular mass replacing each transition zone and is composed of numer- ous individual nodules. Only the nodular component is rec- ognizable histologically as a deviation from normal pattern; internodular tissue, even when increased in amount, is not distinguishable microscopically from normal transition zone. The enlargement of transition zone BPH produces a char- acteristic progressive deformity of overall prostate contour. The expansion is chiefly anterior and toward the apex result- ing in stretching and thinning of the anterior fibromuscular stroma and producing an increase in the thickness (antero- posterior dimension) of the gland. The anterolateral “horns” of the peripheral zone (Fig. 35.9B) are compressed and thinned concomitant with increase of overall prostate width. Basal cell hyperplasia is most often seen as a secondary change in BPH nodules or inflammatory foci (45). The basal cells of ducts and acini become rounded with oval nuclei, and they form a multilayered lining (Fig. 35.35) that stains for basal cell–specific high—molecular-weight cytokeratins. There is typically a single luminal row of columnar secretory cells that stain positive for PSA. When ischemia or frank infarcts are present (often in association with BPH), squamous metaplasia may also become prominent. This benign metaplastic change may closely mimic urothelial carcinoma (Fig. 35.36) (46). Because many men with prostate cancer are treated by radiation therapy, pathologists must be familiar with its effects on benign glands. After radiation, the normal glands typically become atrophic, but with cytoplasmic eosino- philia that imparts a “squamoid” appearance, and scattered nuclei become enlarged and hyperchromatic, albeit with degenerative-appearing, “smudgy,” chromatin (Fig. 35.37). Many of the cells within these glands assume a basal cell phenotype, so the expression with basal cell markers, includ- ing GATA3, is common. Because of the cytologic atypia, the latter immunophenotypic finding may cause confusion with urothelial carcinoma (47,48).

CONSIDERATIONS IN TRANSURETHRAL RESECTION AND NEEDLE BIOPSY SPECIMENS

Tissue distortion by thermal artifact near the edges of trans- urethral resection (TUR) tissue fragments (“chips”) can create important diagnostic problems that occasionally may be insurmountable. Basal cell hyperplasia, adenomatous hyperplasia, atrophy, and fragments of BPH nodules with small glands may be difficult to distinguish from carcinoma without utilizing adjunctive immunohistochemical stains. Loss of nuclear detail occurs more homogeneously across the tissue chips than obvious cell distortion. Hence, small foci of cancer may be more difficult to diagnose because of the artifactual absence of nucleoli.

FIGURE 35.37  Radiation therapy induces atrophic changes in benign prostatic glands, often with associated cytoplasmic eosinophilia and nuclear pleomorphism.