Are locoregional cutaneous metastases in melanoma predictable?

In-transit metastases and satellite lesions are manifestations of locoregional cutaneous recurrence that are characteristic of malignant melanoma. They are the result of tumor cell emboli entrapped in the dermal lymphatics between the primary tumor and the regional lymph node basin. Histopathological features of lymphatic invasion were investigated to determine the possibility of predicting locoregional cutaneous metastases in melanoma patients.

In a prospective study, 258 patients with clinical stage I melanoma underwent wide local excision and sentinel node biopsy. Nodal metastases were found in 53 (21%) patients. Of 29 patients (11.2%) who had developed recurrences to date, 17 (6.6%) had locoregional cutaneous metastases. All surgical specimens were examined with particular attention to histopathological signs of lymphatic vascular invasion or microscopic satellites.

Unequivocal signs of lymphatic invasion were observed in 14 of 258 patients (5.4%), and 13 (93%) of these patients subsequently developed in-transit metastases, after a median interval of 10 months. The primary melanoma was located on the extremities in seven patients. The median Breslow thickness was 2.5 mm, and 5 showed ulceration. In 244 of 258 patients (94.6%), there were no signs of lymphatic invasion. To date, only four patients (1.6%) have had a locoregional cutaneous recurrence, occurring after a median interval of 29 months. All four of these patients had ulcerative melanomas on an extremity, with a median thickness of 4.0 mm. The presence of lymphatic invasion was significantly related to early locoregional cutaneous relapse (P < .0001).

Locoregional cutaneous recurrence appears to be highly predictable in the presence of histopathological signs of lymphatic invasion. Lymphatic invasion is an important prognostic parameter and should be included as a stratification criterion when selecting patients for adjuvant (locoregional) therapy.