 The presence of malignant cells in lymph nodes is a critical parameter in the staging of melanoma cancer patients. Assessment of lymph nodes is currently done by histopathology alone. The long-term survival of melanoma cancer patients who have Stage IB disease no known lymph node involvement with a tumor greater than 2 cm is lower than patients who are Stage IA no known lymph node involvement with a tumor less than 2 cm. Likewise, the survival rates of patients who are judged to be Stage II based on histologically positive level-one lymph nodes is often no better than that of higher stage patients who have level-two lymph node involvement. These observations suggest that micrometastases are often present in lymph nodes that are not detectable by histological assessment. 