[Expression of cancer testis (CT) antigens in pediatric and adolescent melanomas]

One of the main problems in the diagnostics of pediatric melanomas is the differentiation from benign dermal lesions typical for this age group, such as Spitz nevus. The biological behavior of pediatric melanomas differs considerably from that of melanomas in adults.

Cancer testis (CT) antigens are named after their typical expression pattern since they are present in various types of malignant tumors but in normal adult tissues are solely expressed in testicular germ cells. Because of this tumor-associated expression pattern, CT antigens are regarded as potential targets for vaccine-based immunotherapy of cancer and might be used as diagnostic tools in surgical pathology. In adults, melanoma is among the tumors showing a high incidence of CT antigen expression; however, while there is ample knowledge about adult melanomas, little is known about the presence of CT antigens in pediatric melanomas. Consequently, the expression of CT antigens MAGE-A1, MAGE-A4, CT7/MAGE-C1, NY-ESO-1, and GAGE was analyzed in a series of pediatric melanomas. The study was restricted to cases of metastatic disease and/or fatal outcome. A total of 12 cases were available and immunohistochemically analyzed with monoclonal antibodies (mAb).

The expression of CT antigens was generally low and present in only 4 of 12 cases. This is in stark contrast to the expression of these antigens in adult melanomas. Moreover, the extent of expression was very limited with most cases showing only a focal CT antigen expression and only marked in very small tumor areas (<5%).

Despite the low case numbers this study indicates that CT antigens are most likely not useful as diagnostic markers in pediatric melanomas or as targets for vaccine-based immunotherapy. It supports the notion that pediatric melanomas show a different biological behavior than their adult counterparts.