BACKGROUND: The aim of this study was to determine ERBB-2 (HER-2/neu) gene alterations in different subtypes of uterine sarcomas. METHODS: After central review, representative biopsies were immunohistochemically stained and semiquantitatively scored as negative, weakly (1+), moderately (2+), or strongly (3+) positive. Subsequently, fluorescence in situ hybridization (FISH) was performed on cases with 2+ and 3+ expression. RESULTS: Seventy tumors (52 primaries and 18 recurrent) were evaluated. All 10 adenosarcomas, 21 endometrial stromal sarcomas, and 10 leiomyosarcomas were negative both in the primary and recurrent setting. Twenty-two primary carcinosarcomas were scored. The epithelial component was negative/1+ in 16 (73%), 2+/3+ in five (22.5%) tumors, and could not be evaluated in one case (4.5%), whereas the sarcoma component stained negative/1+ in 21 cases (95.5%) and 3+ (4.5%) in one case. In two recurrent carcinosarcomas, the epithelial component stained 3+ in both cases, whereas the sarcoma component scored negative and 1+. Amplification of the ERBB-2 gene as determined by FISH was observed in 3/7 (43%) carcinosarcomas with 2+ or 3+ overexpression, resulting in an overall 3/22 (14%) amplification rate. One out of four undifferentiated uterine sarcomas stained 2+. ERBB-2 immunopositivity (3+) and ERBB-2 amplification by FISH were confirmed in the recurrent tumor, resulting in a gene amplification rate of 1/4 in undifferentiated uterine sarcomas. CONCLUSION: The current results suggest absence of ERBB-2 overexpression in uterine leiomyosarcoma, uterine adenosarcoma, and endometrial stromal sarcoma, whereas the ERBB-2 gene might have a biologic role in uterine carcinosarcoma and undifferentiated uterine sarcomas.