Epiluminescence microscopy features of cutaneous malignant melanoma metastases

Especially small and/or initial cutaneous malignant melanoma metastases (CMMMs) are tumours with inconspicuous clinical and sometimes histological features which may be difficult to differentiate from benign melanocytic lesions or angiomas. Thus it would be very valuable to have additional criteria for the differential diagnosis of such lesions. Thirty histologically verified CMMMs were examined using epiluminescence microscopy (ELM) in order to visualize a large number of morphological features permitting the recognition of malignancy. One hundred primary cutaneous malignant melanomas (PCMMs), 50 dysplastic naevi, 50 common naevi, 30 blue naevi and 20 haemangiomas served as the control group; these were randomly selected from a large data base and were all reviewed for histological diagnosis. Four of the 24 features studied were shown to differ significantly between CMMMs and the control group. Two features of the malignant tumour group (CMMM and PCMM) differed significantly from the benign tumour group. A polymorphic angiectatic base pattern and/or vascular aneurysms, peripheral erythema, brown-grey coloration as a negative criterion (i.e. its absence is indicative of CMMM) and a light brown halo had a specificity of 86.7-96.0% for CMMM. Areas of polymorphic and/or horizontally dilated capillaries and a saccular pattern had a specificity of 97.3-99.2% for the malignant group (CMMM and PCMM). Three features - peripheral greyish patches, lesions surrounded by grey streaks (melanoma cell infarcts of the vessels) and microscopic ovoid blood lakes (spontaneous microhaemorrhages)--were absent in the benign group. The prevalence of distinct ELM criteria in CMMM represents a useful enhancement for the diagnosis of malignancy in melanocytic skin lesions.