The role of microsatellites as a prognostic factor in primary malignant melanoma.

Objective: To determine the impact of microsatellites as a prognostic factor in primary cutaneous melanoma.

Design: Retrospective cohort study.

Setting: Tertiary referral center. Patients A total of 504 patients with a history of primary melanoma observed for 2 years or having experienced a first relapse.

Main Outcome Measures: Overall survival (OS) and relapse-free survival (RFS).

Results: Forty-five patients had evidence of microsatellites in their primary melanoma. Presence of microsatellites significantly correlated with the presence of several other histologic high-risk factors such as tumor thickness, ulceration, Clark level, vascular factors, and mitotic rate. Univariate analysis demonstrated decreased RFS and OS in patients with microsatellites. Presence of microsatellites was associated with increased locoregional metastasis but not distant metastasis. In multivariate analysis, with the inclusion of 6 other clinical and histologic factors, presence of microsatellites was a significant predictor of RFS but not OS. Patients with clinical macrosatellites had a trend toward worsening OS compared with those with microsatellites.

Conclusions: The presence of microsatellites is intimately tied to other markers of melanoma aggressiveness. Microsatellites appear to predict locoregional relapse and RFS but neither distant metastasis nor OS. These results may have implications for patient care as well as the inclusion of microsatellites in stage III of the current classification.