Detection of lymphatic invasion in primary melanoma with monoclonal antibody D2-40: a new selective immunohistochemical marker of lymphatic endothelium.

OBJECTIVES To identify the presence of lymphatic invasion in primary cutaneous melanoma using monoclonal antibody D2-40, a marker of lymphatic endothelium, and to correlate the presence of lymphatic invasion with other clinicopathologic characteristics of the tumors. DESIGN Retrospective melanoma case series study comparing conventional hematoxylin-eosin staining with D2-40 immunostaining for detection of lymphatic invasion. SETTING Departments of Pathology and Dermatology, Sunnybrook and Women's College Health Sciences Center, University of Toronto, Toronto, Ontario. Patients Forty-four consecutive cases of primary cutaneous melanoma with a tumor thickness greater than 0.75 mm were examined for presence of lymphatic invasion. RESULTS Seven (16%) of 44 melanomas showed the presence of lymphatic invasion under immunostaining with D2-40. In 2 cases, subepidermal lymphatic involvement was present; in 5 cases lymphatic invasion was noted within the tumor, including 1 case of additional lymphatic invasion at the invasive edge of the tumor. Lymphatic invasion was not detected on routine hematoxylin-eosin staining. We observed a trend in the association between lymphatic invasion and 2 markers of tumor aggressiveness, namely, a deeper Clark level and increased frequency of ulceration, which suggests that lymphatic invasion detected with D2-40 may indicate a poor prognosis. CONCLUSIONS Immunostaining with D2-40 increases the frequency of detection of lymphatic invasion relative to conventional hematoxylin-eosin staining in primary melanoma. Future outcome data will determine the prognostic significance of lymphatic invasion detected by D2-40 immunostaining.