OBJECTIVETo study the expression of prostate stem cell antigen (PSCA) at protein and mRNA levels in invasive micropapillary carcinoma of the breast (IMPC) and to analyze the relationship between PSCA expression and clinicopathologic features.

METHODSThe expression of PSCA protein was analyzed by immunohistochemistry (LSAB) in 66 cases of IMPC and 67 cases of invasive ductal carcinoma, not otherwise specified (IDC-NOS). The association between PSCA expression and clinicopathologic features was also analyzed in IMPC. Furthermore, RT-PCR was used to detect PSCA mRNA in 10 cases of primary IMPC and 10 cases of primary IDC-NOS with paired normal breast tissues, each from the same subject.

RESULTSImmunohistochemical analysis revealed the overexpression of PSCA in 47 of 66 (71.2%) cases of IMPC and 35 of 67 (52.2%) IDC-NOS. Statistical analysis showed a significant difference of PSCA expression between IMPC and IDC-NOS (P = 0.024). In IMPC, the expression of PSCA was correlated with lymph nodes metastasis (P = 0.039). RT-PCR showed the mRNA level of PSCA was significantly higher in primary IMPC and IDC-NOS tissue than that in paired normal breast tissue (7/10 and 5/10, respectively), and it was also significantly higher in primary IMPC tissue than that in IDC-NOS tissue.

CONCLUSIONPSCA might play an important role in lymph node metastasis in IMPC.