Histologic features of stromogenic carcinoma of the prostate (carcinomas with reactive stroma grade 3).
Prostatic carcinoma, like many other carcinomas, generates a stromal reaction. This phenomenon is well established in the scientific literature. The normal parenchymal smooth muscle phenotype switches to a myofibroblastic phenotype in response to the presence of cancer cells, with an expansion of the extracellular matrix compartment. The amount of reactive stroma is a predictor of biochemical recurrence in both radical prostatectomies and biopsies. It is a predictor of prostate cancer-specific death in prostatectomies. The aim of this study is to improve our histologic understanding of reactive stroma in prostate cancer and to determine the histologic features of the malignant epithelium found in stromogenic carcinomas or carcinomas with reactive stromal grade 3. Tissue microarrays of 800 patients and hematoxylin and eosin-stained sections of 120 radical prostatectomies, previously determined to contain a high proportion of areas with stromogenic carcinoma, were evaluated and findings systematically recorded. We identified 3 histologic patterns of reactive stroma: extracellular matrix-rich, cellular variant and edematous/myxoid variant. The most common pattern of carcinoma in stromogenic areas is of the acinar type with angulated glands and periglandular halos. The nuclei are enlarged, opened, with prominent nucleoli. Luminal borders are undulated, and amorphous pink secretion is often seen. Perineural invasion is frequently identified. Because of the clinical relevance, identification and quantification of areas with high reactive stromal grade by pathologists and reproducibility of our findings by others become essential. We believe that with the previously proposed grading system and the present morphologic description, both can be achieved.