Activated leukocyte cell adhesion molecule/CD166, a marker of tumor progression in primary malignant melanoma of the skin

Expression of activated leukocyte cell adhesion molecule (ALCAM)/CD166 corr elates with the aggregation and metastatic capacity of human melanoma cell Lines (Am J Pathol 1998, 152:805-813). Immunohistochemistry on a series of human melanocytic lesions reveals that ALCAM expression correlates with mel anoma progression. Most nevi (34/38) and all thin melanomas studied (Clark levels I and II) did not express ALCAM. In contrast, immunoreactivity was d etected in the invasive, vertical growth phase of 2 of the 13 Clark level I II lesions tested. The fraction of positive lesions further increased in Cl ark level IV (13/19) and in Clark level V (4/4) lesions. ALCAM expression w as exclusively detectable in the vertical growth phase of the primary tumor . In melanoma metastases, approximately half of the lesions tested (13/28) mere ALCAM positive. According to the Breslow-thickness, ALCAM expression w as observed in less than 10% of the lesions that were thinner than 1.5 mm a nd in over 70% of the lesions that mere thicker than 1.5 mm. Our results st rongly suggest that ALCAM plays an important role in melanocytic tumor prog ression and depict it as a new molecular marker for neoplastic progression of primary human melanoma.