Previous evaluation of HER2 overexpression in salivary gland cancers indicated an incidence varying between 7 and 56%, with no clear difference among three histologically different subtypes. As part of a Phase II trial of trastuzumab for treatment of incurable salivary gland cancer, we screened 137 tumors for HER2 expression.Unstained sections of paraffin-embedded tumor samples were stained with p185/HER2 receptor antibody. Tumors with moderate (2+) to strong (3+) complete membrane staining in at least 10% of the tumor cells were scored as positive for overexpression.The overall frequency of overexpression for HER2 was 17% (23 of 137), whereas it was only 8% in the three most common histological subtypes screened. Overexpression was distinctly rare in the most common subtype screened, adenoid cystic carcinoma (4%, 3 of 70). Overexpression was very common in salivary duct cancers; 10 (83%) of 12 were positive for HER2. This observation is consistent with the typical high-grade histological features and aggressive behavior of this subtype as well as with its histogenetic similarity to breast cancer. Analysis based on histogenesis (intercalated duct versus excretory duct) indicated a higher frequency of overexpression in the latter (55%) than in the former (7%).Our overall results suggest that trastuzumab will not have a major role in treatment of salivary gland cancers of intercalated duct origin. Further systematic evaluation of trastuzumab in subtypes of excretory duct origin could be supported.
View details for Web of Science ID 000188982700017
View details for PubMedID 14871971