HER-2/neu overexpression and amplification in uterine serous papillary carcinoma: comparative analysis of immunohistochemistry, real-time reverse transcription-polymerase chain reaction, and fluorescence in situ hybridization.

Uterine serous papillary carcinoma (USPC) is a rare and highly malignant form of endometrial cancer (EC) characterized by early metastasis, chemoresistance, and high mortality rate. Little is known about USPC tumorigenesis even if recently a HER-2/neu role has been suggested in its development and progression. The aim of the present study was to evaluate HER-2 expression by immunohistochemistry (IHC) in 12 USPC formalin-fixed, paraffin-embedded (FFPE) samples. Moreover, we looked at the correlation between HER-2 protein expression and HER-2/neu gene amplification by fluorescence in situ hybridization (FISH), other than HER-2/neu messenger RNA expression by quantitative real-time reverse transcription (RT)–polymerase chain reaction (PCR). Finally, these results have been compared with commonly evaluated clinical features in EC patients, in order to define the potential prognostic value of HER-2/neu overexpression in USPCs. A high expression of HER-2 protein by IHC was noted in 2 of 12 patients (16.6%), and the same cases showed specific HER-2/neu gene amplification by FISH. All the samples investigated displayed a perfect concordance between IHC and FISH data. Five (41.6%) of 12 tumors demonstrated polysomy of chromosome 17 and, focusing on the 2 USPCs that showed HER-2/neu overexpression, one of them (50%) was polysomic for chromosome 17. All the other USPC cases (58.4%) showed to be disomic for chromosome 17. Quantitative RT real-time PCR performed on complementary DNA obtained from all FFPE USPC samples showed a complete correlation with FISH and IHC data. Moreover, HER-2/neu overexpression was associated with a poorer overall survival and a very low relapse-free survival time, thus being considered a candidate marker of worse overall prognosis in USPC. The use of trastuzumab (Herceptin), a monoclonal antibody directed against HER-2/neu, for the therapy of patients with HER-2/neu-positive USPCs should be further investigated in clinical trials.