We evaluated the usefulness of overexpression of neuroendrocrine (NE) cell differentiation determined by immunohistochemical staining for chromogranin A (Cg A) in diagnostic needle biopsy specimens of bone metastatic prostate cancers. A total of 50 patients diagnosed as having bone metastatic prostate cancer were studied. The period of observation was between 6.9 and 79.4 months (median 48.7 months). Cg A was detected by immunostaining using the labeled streptavidin biotin method. Cg A-positivity was defined as the presence of immunostained cells in 10% or more of the tumor. All statistical analyses were carried out using the Statistical Package for Social Sciences Software, version 10.0 for Windows. Eleven patients (22%) were classified into the Cg A-positive group. There were no significant differences in clinical data between the Cg A-positive and Cg A-negative groups. The 5-year cause-specific survival rate was 34.1% for the Cg A-positive group and 55.2% for the Cg A-negative group (p=0.3763). The 3-year non-recurrence rate was 9.1% for the Cg A-positive group and 35.9% for the Cg A-negative group, and this difference was significant (p=0.0253). The 3-year cause-specific survival rates after recurrence were 38.4% and 42.3% respectively (p=0.8125). We consider that NE cell differentiation of the primary tumor in cases of bone metastatic prostate cancer is not a prognostic factor for outcome.

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