Frequency and morphologic characteristics of invasive melanomas lacking specific Surface microscopic features

Objectives: To create a simple diagnostic method for invasive melanoma with in vivo cutaneous surface microscopy (epiluminescence microscopy, dermoscopy, dermatoscopy) and to analyze the incidence and characteristics of those invasive melanomas that had no diagnostic features by means of hand-held surface microscopes. Design: Pigmented skin lesions were photographed in vivo with the use of immersion oil. All were excised and reviewed for histological diagnosis. A training set of 62 invasive melanomas and 159 atypical nonmelanomas and a test set of 45 invasive melanomas and 119 atypical nonmelanomas were used. Images from the training set were scored for 72 surface microscopic features. Those features with a low sensitivity (0%) and high specificity (>85%) were used to create a simple diagnostic model for invasive melanoma. Setting: All patients were recruited from the Sydney (Australia) Melanoma Unit (a primary case and referral center). Patients: A random sample of patients whose lesions were excised, selected from a larger database. Main Outcome Measures: Sensitivity and specificity of the model for diagnosis of invasive melanona. Results: The model gave a sensitivity of 92% (98/107) and specificity of 71%. Of the 9 ''featureless'' melanomas the model failed to detect, 6 were pigmented and thin and had a pigment network. The other 3 were thicker, hypomelanotic lesions lacking a pigment network, some with prominent telangiectases, and all with only small areas of pigment. All featureless melanomas noted by the patients had a history of change in color, shape, or size. Conclusions: Surface microscopy does not allow 100% sensitivity in diagnosing invasive melanoma and therefore cannot be used as the sole indicator for excision. Clinical history is an important consideration when featureless lesions are diagnosed.