Type VII collagen antibody LH 7.2 identifies basement membrane characteristics of thin malignant melanomas.

A monoclonal antibody (LH 7.2) to the carboxy terminal of type VII collagen has been used in an indirect immunoperoxidase method on frozen sections of biopsies of benign compound and intradermal cellular naevi, dysplastic naevi, and malignant melanomas, to label the epidermal basement membrane. Benign intradermal naevi had an intact membrane with the dermal naevus cell component lying beneath it. Compound naevi showed proliferating junctional nests of naevus cells pushing through the membrane towards the dermis beneath. In contrast, dysplastic naevi and melanomas showed a progressive displacement of the membrane downwards. Thin lesions were confined above the membrane. With increasing tumour thickness, discontinuities in the membrane were seen and foci of invasive growth through the line of the membrane were identified. These studies suggest that the good prognosis of thin melanomas is associated with confinement of the tumour within an expanded epidermis above the basement membrane.