The Morphologic Criteria of the Pseudopod in Surface Microscopy

BACKGROUND AND DESIGN: In vivo cutaneous surface microscopy (oil epiluminescence, dermatoscopy, and dermoscopy) has been shown to greatly enhance the clinical diagnosis of melanoma. The pseudopod is a morphologic feature seen on surface microscopy that corresponds to the radial growth of tumor in melanoma. While it is one of the most specific surface microscopic features of invasive melanoma, it has remained poorly defined. We studied 239 pigmented lesions, 80 melanomas (62 invasive and 18 in situ) and 159 randomly selected pigmented nonmelanomas. We photographed these lesions in vivo using immersion oil and a Heine Dermaphot camera (Heine Ltd, Herrsching, Germany). We then scored the lesions in a "blinded" fashion for the presence of pseudopods based on strictly defined morphologic criteria. RESULTS: We defined the morphologic criteria of the pseudopod. As defined, the pseudopod retained a 97% specificity and 23% sensitivity for invasive melanoma. No difference was seen in the mean Breslow thickness between melanomas with and without pseudopods. None of the in situ melanomas were observed to have pseudopods. CONCLUSION: We suggest morphologic criteria for a highly specific in vivo cutaneous surface microscopic feature of invasive melanoma, the pseudopod.