Macroscopic spectral imaging and gene expression analysis of the early stages of melanoma

Background: The stages of melanocytic progression are defined as atypical ( dysplastic) nevus, melanoma in situ, melanoma in the radial growth phase (R GP), melanoma in the vertical growth phase (VGP), and melanoma in the metas tatic growth phase (MGP). Melanoma in situ and RGP melanoma often develop i n contiguous association with atypical nevi. This frequently poses a proble m with respect to their early detection. Furthermore, unlike cells obtained from VGP and MGP melanomas, cells derived from melanoma in situ and RGP me lanoma do not proliferate in vitro. Thus, compared to the late stages of th e disease, less information is available regarding genes expressed in the e arly stages. Materials and Methods: To determine whether spectral imaging, a recently de veloped optical imaging technique, can detect melanoma in situ and RGP mela noma arising in melanoma precursor lesions, atypical nevi in patients with a clinical history of melanoma were subjected to noninvasive macroscopic sp ectral imaging. To determine at what stage in the progression pathway of me lanoma genes having important biological functions in VGP and MGP melanomas are activated and expressed, lesions of melanoma in situ were analyzed by immunohistochemistry! and in situ hybridization for expression of some of t hese known molecular and immunologic markers. Results: The present study demonstrates the capability of noninvasive spect ral imaging to detect melanoma in situ and RGP melanoma that arise in conti guous association with atypical nevi. Furthermore, the study provides evide nce that genes and antigens expressed in VGP and MGP melanoma are also expr essed in melanoma in situ. Conclusions: Because of the dark and variegated pigmentation of atypical ne vi, melanoma in situ and RGP melanoma that arise in these melanoma precurso r lesions are often difficult to recognize and thus frequently go unnoticed . The application of new optical screening techniques for early detection o f melanoma and the identification of genes expressed in the early stages of melanoma development are two important avenues in the pursuit of melanoma prevention. The investigations presented here document that macroscopic spe ctral imaging has the potential to detect melanoma in its early stage of de velopment and that genes essential for the proliferation and cell adhesion of VGP and MGP melanoma are already expressed in melanoma in situ.