In order to elucidate the role of the receptor tyrosine kinase HER3, the expression characteristics in different tissues of cutaneous malignancies and in normal skin were compared.In this study HER3 expression was evaluated by RT-PCR analysis and immunohistochemistry from different tissue specimens of cutaneous tumors like nevi, primary malignant melanomas, basal cell carcinoma, squamous cell carcinoma and malignant melanoma metastases and normal skin samples and graded into weak, moderate and strong expression. Associations of tumor thickness in these specimens with HER3 expressions were also analyzed.HER3 expression was found in 63% (10/16) of the basal cell carcinomas, in 4/5 of squamous cell carcinomas and in one Merkel cell carcinoma. Within the group of different malignant melanomas, HER3 expression was detected in 35% of the nodular malignant melanomas (6/17) and in 9/19 of the superficial spreading melanomas, including 2 lentigo malignant melanomas. The majority of melanomas with a higher tumor thickness expressed HER3, and 85% of melanoma metastasis were HER3-positive.HER3 expression was associated with hyperproliferate tumor stages and suggested that HER3 expression could reflect an increased malignant potential in cutaneous lesions.