Predictive value of immunohistochemical detected melanoma satellite metastases
Department of dermatopathology, University of Liège, Liège, Belgium
A satellite micrometastasis is defined as a nest of tumor cells separated from the main tumor mass and measuring at least 0.05mm. Such a breakpoint in size might appear biologically irrelevant since it depends on the sensitivity of the technique used.AIM With a panel of antibodies directed to melanocyte- associated antigens we were able to detect single cell micrometastases. METHODS A total of 266 melanoma cases and their sentinel node (in 68 cases) were studied over a 2 year period for the presence of micrometastases.RESULTS 34 cases (12%) showed satellite metastases of which more than 80 % remained undetected by conventional microscopy. Invasion of the sentinel nodes were found in 14%( 10/68). AII these positive cases were exclusively found in the 33 out of 68 melanomas of more than 1 mm thickness. However satellite micrometastases were found in 8% in T1. Among the cases with positive nodes 60%( 6/10) had positive satellite metastases in contrast to only 29%( 17/58) when the sentinel node was not invaded.CONCLUSIONS The fact that in more than half of cases there is the simultaneous presence of microsatellites and nodal invasion suggests that satellite metastases might result of lymphatic dissemination and thus be equivalent to in-transit metastases as suggested by the recent AJCC classification. Conversely as demonstrated by the latter 17 positive cases without lymph node involvement, these satellite cells might remain dormant or eventually grow, form aggregates and spread, thus representing the earliest step in dissemination, whether it be lymphatic, hematogenous or extravascular. We contend that patients with satellite micrometastases without lymph node involvement are more prone to develop metastases and should be monitored more closely.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in oral session 893 (Molecular pathology - Part I).