Micro-melanoma detection. A clinical study on 22 cases of melanoma with a diameter equal to or less than 3 mm

Very small pigmented lesions may represent an extreme diagnostic challenge to the clinician. Our aim was to describe the clinical and dermoscopic features in a series of cutaneous melanomas with a maximum clinical diameter of 3 mm.

We conducted a retrospective study of the 924 primary melanomas seen and treated during a period of five years at the Unit for Melanoma Detection of the Istituto Nazionale Tumori of Milan, Italy. The size characteristics of the considered lesions allowed the identification of 22 (2.4%) cases of micro-melanoma (clinical diameter of 3 mm or less). Sixteen of these cases were subjected to dermoscopy. The clinical and dermoscopic features as well as the corresponding diagnoses were recorded.

The typical lesion presents as a small, dark, often black macule, generally evenly colored, with well-defined borders; it may be asymmetric or symmetric in shape. These features prompted a correct clinical diagnosis in nearly half of the cases. Dermoscopy lead to a correct diagnosis in all cases subjected to the technique.

Dermoscopy appears to be an efficient aid to the diagnosis of micro-melanomas, provided that clinicians are aware of this type of lesion and maintain the index of suspicion at a high level.