The 10-year survival rate of patients with primary melanoma without detectable metastasis is 75 percent. The survival rate drops dramatically in patients with lymph node metastases. In these patients, the number and volume of involved lymph nodes are the most important factors in recurrence and survival time. Therefore, early detection of metastases in the lymphatic drainage areas or regional lymph nodes is of critical importance. Several studies have shown that palpation of these areas during the follow-up of melanoma treatment is associated with a high rate of false-negative results. As a result, Blum and colleagues compared the sensitivity and specificity of ultrasound diagnosis with that of clinical impression in the detection of subcutaneous and regional metastases of melanoma.

Patients with a histologically confirmed diagnosis of cutaneous melanoma following surgical resection were eligible for the prospective study. Those who met the inclusion criteria were followed every three months for the first five postoperative years, and then every six months for the next five years. An ultrasound examination was performed at the area of the scar of the resected tumor, the lymphatic drainage area and the regional lymph nodes once a year in patients with low-risk melanoma (tumor thickness less than 1.5 mm) and every three to six months in those with high-risk melanoma (tumor thickness 1.5 mm or greater). If metastatic disease was suspected, the area was surgically excised for histologic examination. The areas were examined clinically as well. The results of both examinations were compared with the histopathology of the removed lymph nodes.

Of the 1,288 patients enrolled in this study, 235 revealed findings on ultrasound examination suggesting metastases. One or more nodules or lymph nodes were removed surgically in 263 examinations, with metastatic findings in 179 patients. Melanoma metastasis was confirmed in 91 percent of the nodules or lymph nodes identified as positive on ultrasound examination. A second malignancy was discovered in 3 percent of the nodules, and benign reactive lymphadenopathy was found in 6 percent. The sensitivity of ultrasound examination was 89.2 percent, and the specificity was 99.7 percent. Twenty-nine percent of the cases of proven metastatic disease were not found on clinical examination. The least sensitive areas on clinical examination were in the supraclavicular, axillary and infraclavicular areas, respectively.

The authors conclude that ultrasound examination of the lymphatic drainage area and regional lymph nodes is superior to clinical examination in the early detection of lymph node metastasis in cutaneous melanoma. They further recommend that ultrasound examination become part of a regular follow-up protocol in these patients. Additional research is needed to determine whether the use of ultrasound examination in these patients will improve survival rates.