Confocal microscopy accurately detects melanoma

Skin cancer that is detected early is almost always curable. However, biopsy is the standard method for detection and, because benign lesions are hard to differentiate from cancerous ones, many patients undergo unnecessary excisions. Dr. Giovanni Pellacani from the University of Modena and Reggio Emilia in Italy and his colleagues evaluated how well noninvasive reflectance confocal microscopy could differentiate between malignant and benign lesions in comparison with standard diagnostic methods.

As reported in the July 26 online version of the Journal of Investigative Dermatology, the researchers imaged 351 equivocal melanocytic lesions from 332 patients, using near-infrared reflectance confocal laser scanning microscopes from Lucid Inc. of Henrietta, N.Y., which included an 830-nm laser with about 35 mW of power. More than 100 images were captured over a 4 × 4-mm area for each lesion. Biopsies then were performed on each lesion for histologic comparison.

Researchers discovered that reflectance confocal microscopy can accurately detect melanoma. This confocal image shows malignant cells — represented by the bright structures — in the leg of a 68-year-old woman. Several cells have a dark center portion (the nucleus) and are predominantly located in the epidermis and dermal-epidermal junction — a strong diagnostic clue for melanoma diagnosis. Image courtesy of Giovanni Pellacani.

Two expert observers, who were not given the histologic diagnoses or any patient information (except the locations of the lesions and the patients’ ages), evaluated the images. They looked for 37 different confocal features, which had been established as possible melanoma predictors by previous studies, for indications of whether the lesions were cancerous or benign. Some of the main features that characterized melanoma were epidermal (outer skin) disarray and pagetoid cells (upward-spreading melanoma cells) in the epidermis; nonedged papillae (disarray of the dermal-epidermal contour); and atypical nests (irregularly shaped clusters of cells) and bright nucleated cells infiltrating the dermis (inner skin).

The researchers used SPSS Inc. statistical software to evaluate the significant differences between the melanomas and the benign lesions detected. They compared the evaluated confocal images with the standard histologic diagnoses and found that the reflectance confocal method clearly detected 131 out of 136 melanomas. Pellacani said the results mean that confocal microscopy could help patients avoid more than 50 percent of unnecessary excisions involving benign lesions.

The researchers believe their results indicate that reflectance confocal microscopy may be a good noninvasive alternative for more accurately identifying melanocytic lesions that actually do need surgical excision.