BACKGROUNDThe aim of this study was to investigate DNA content and expression of c-erbB-2, PS2, and prostate-specific antigen (PSA) proteins in breast carcinomas with neuroendocrine (NE) cell differentiation.

METHODSChromogranin, c-erbB-2, PS2, and PSA in 131 samples of breast cancer were detected immunohistochemically. Classic Feulgen staining image analysis techniques were used to quantify DNA content in 81 of the breast cancer samples.

RESULTSThe c-erbB-2 positive rate in breast carcinoma samples containing neuroendocrine cells was 37.5% and the rate of high expression of c-erbB-2 (++ or +++) was 33.3%, both significantly lower than that in breast carcinomas without neuroendocrine cells (62.6% and 68.7%, respectively, P < 0.05). The rates of positive PS2 and PSA expression in breast carcinoma samples containing neuroendocrine cells were 72.2% and 55.0%, respectively, both significantly higher than that in breast carcinoma samples without neuroendocrine cells (45.0% and 16.4%, respectively, P < 0.05). In NE(+) samples, the integral optical density, DNA index, DNA stemline peak, > 5 c aneuploidy cells, and rate of aneuploidy among cells were all lower than that in NE(-) breast carcinomas (P < 0.01). In NE(+) grade I or II breast carcinomas, these indices were also all lower than that in the NE(-) breast carcinoma samples (P < 0.01).

CONCLUSIONBreast carcinomas with neuroendocrine differentiation have a lower rate of malignancy. Neuroendocrine differentiation could serve as a prognostic marker in clinical practice.