[550] Pathological Features of the Primary Melanomas of Patients Studied in the Multi-Center Sentinel Lymphadenectomy Trial-1 (MSLT-1) and Their Relationship to Sentinel Node Tumor Status and Clinical Outcome

Chandra N Smart, Alistair J Cochran, Eijun Itakura, Duan-Ren Wen, MSLT-1 Study Group Pathologists, Donald L Morton. UCLA/David Geffen School of Medicine, Los Angeles, CA; John Wayne Cancer Institute, St. John's Medical Center and Hospital, Santa Monica, CA; Johnson Comprehensive Cancer Center, Los Angeles, CA

Background: The MSLT-1 (Multi-center Sentinel Lymphadenectomy Trial) was recently completed. We documented the demographics of trial patients and microscopic features of their primary tumors.
Design: 2001 trial patients were randomized into two groups. After exclusion criteria were applied, 260 patients were excluded and 28 patients were either ineligible or dropped out. The SNB group (n=1028) comprised patients who underwent wide local excision and sentinel node biopsy, followed by lymphadenectomy if the sentinel node was positive. The second group (n=685) were patients who underwent wide local excision, followed by clinical observation with lymphadenectomy when nodal metastases became clinically evident. We recorded: patient age, gender, primary site, Breslow thickness, Clark level, mitotic rate and histologic subtype of the tumor and the presence/absence of ulceration, lymph/vascular invasion, regression, peri/intra-tumor lymphocytic infiltrates, and microscopic satellites.
Results: In the SNB group, 189 patients had a positive SLN and 839 a negative SLN. In the SNB, node positive group, the mean age was 49.5 +/- 14.1 years. The commonest primary tumor sites were trunk 47.1% (n=89) and extremities 40.7% (n=77). Mean Breslow thickness was 3.14 +/- 2.05 mm with most tumors Clark level IV (63.5%). Lymphatic invasion was present in 25 patients (13.6%). The Cochran-Armitage trend test showed that the likelihood of a positive sentinel lymph node significantly correlated with number of risk factors: age <50, trunk primary, Breslow >2, Clark >III, and lymphatic invasion. Significantly, with 0 risk factors, the chance of positive lymph nodes is 6.6%, 1 risk factor, 11.6%, 2 risk factors 14.7%, 3 risk factors 28.5%, 4 risk factors 45.6% and 5 risk factors 80%.
Conclusions: The results of this study confirm our previous findings and data from the literature. Significant risk factors for sentinel node metastasis include patient age, lymphatic invasion, primary site, Breslow thickness and Clark level. The likelihood of a tumor positive sentinel node significantly correlates with the number of risk factors present. These findings are clinically relevant and indicate the need for nodal assessnent, only sentinel node biopsy can determine actual presence of nodal metastases.
Category: Dermatopathology

Monday, March 19, 2012 8:45 AM

Platform Session: Section F, Monday Morning

 

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