[The difficulty of ultrasound diagnosis of lymph node metastases of malignant melanoma in protracted tumor growth].

Lymph node ultrasound examinations are performed during the follow-up of cutaneous melanoma in order to early recognise regional metastases. The excision of regional metastases is the only way to inhibit disseminated metastasis in a certain percentage of cases. Lymph node ultrasound has a sensitivity of 95% in the diagnosis of pathological lymph node changes. Sonographic findings normally show typical features of malignancy; only in some doubtful cases are further control examinations warranted over a period of 4-6 weeks. In violation of this rule, two cases are presented with a delayed onset of metastases causing difficulties in the diagnosis of malignant transformation. Four years after the excision of a nodular melanoma with 0.8 mm tumor thickness at the right lower leg, a suspicious lymph node change in the right groin was sonographically detected which did not fulfill all criteria of malignancy. Control examinations over a period of 1 year found only a further growth of 3 mm. Excision after 1 1/2 years showed a lymph node metastasis. The second case presented 9 years after the excision of a superficial spreading melanoma with 0.76 mm tumor thickness with a suspicious lymph node in the right axilla which similarly grew very slowly. The subsequent excision showed likewise a melanoma metastasis. A protracted growth may occur in thin malignant melanomas with late development of ultrasound features of malignancy. In doubtful cases an early biopsy is recommended.