Lymphatic invasion is independently prognostic of metastasis in primary cutaneous melanoma.

PURPOSE: Lymphatic invasion (LI) in primary cutaneous melanomas was recently found to be common. In this study, we evaluated LI as an independent prognostic factor. EXPERIMENTAL DESIGN: This study included 251 patients with vertical growth phase (VGP) primary cutaneous melanomas who had paraffin-fixed lesional tissue and were in a prospective cohort seen between 1972 and 1991, had no clinical evidence of regional nodal disease at diagnosis, and had at least ten years of follow-up. Dual immunohistochemical staining was used to detect lymphatic endothelium (podoplanin) and melanoma cells (S-100). Multivariate logistic regression for ten-year metastasis was used to define independent prognostic factors, and a prognostic tree was developed to characterize and discriminate risk groups. Kaplan-Meier disease-free survival curves for those with and without LI within current American Joint Committee on Cancer stages were compared using the log-rank statistic. RESULTS: LI was observed in 43% (108 of 251) of the study melanomas. The multivariate model for ten-year metastasis identified four independent prognostic factors: tumor thickness, mitotic rate, LI, and anatomic site. The prognostic tree identified a group of patients with thin (≤1 mm thick) melanomas and poor prognosis: stage IB melanomas with LI. Survival curves for time to first metastasis showed significantly poorer prognosis for patients with LI compared with those without it for both stages IB and IIA. CONCLUSIONS: LI is common across the range of tumor thicknesses in primary VGP melanomas. It is an independent prognostic factor and significantly increases the risk of metastasis in patients in clinical stages IB and IIA.

Induction of melanoma phenotypes in human skin by growth factors and ultraviolet B.

Exposure to UV radiation likely plays a key role in melanoma development, whereas other etiologic agents remain unknown. Here we show that in normal human skin an increased expression of a combination of three growth factors, basic fibroblast growth factor, stem cell factor, and endothelin-3, along with exposure to UVB can transform normal melanocytes into a melanoma phenotype within 4 weeks. Invasion of melanoma lesions was found in skin from newborn donors, whereas melanomas in adult skin were of a noninvasive in situ type only. This suggests that susceptibility of skin to exogenous tumor promoters is dependent on age. This is the first report on human cancer initiation in vivo in which an imbalance of physiological factors combined with an environmental carcinogen can lead to transformation of normal tissue.