Immunohistochemical and ultrastructural features of neuroendocrine differentiated carcinomas of the prostate: an immunoelectron microscopic study.

The purpose of this study was to further define the immunohistochemical and ultrastructural characteristics of neuroendocrine (NE) differentiated prostatic carcinomas. Seventy-seven specimens were obtained from prostatic carcinoma tumors during prostatectomy, transurethral resection of prostate or biopsy in 77 prostate cancer patients, and analyzed by immunohistochemical staining for chromogranin A (CgA). Nine of these tumors were also studied by elctron microscopy and 4 were examined by pre-embedding immunoelectron microscopy. CgA-stained cells were detected in 36 tumors (47%). Clinically advanced tumors or tumors with higher histological grades were associated with increased NE differentiation. Three of the tumors studied by electron microscopy contained cells showing unequivocal NE differentiation revealed by the presence of neurosecretory granules, while the poorly NE-differentiated malignant cells contained pleomorphic granules, which were lysosomal-like rather than NE-type granules. Immunoelectron microscopy demonstrated the presence of CgA immunoreactivity on the pleomorphic granules in the poorly differentiated malignant glands. This study suggests that NE-differentiated malignant cells in prostate cancer tissues may induce aggressive behavior in adjacent proliferating neoplastic cells via a paracrine mechanism.