RCM superior to dermoscopic, clinical exam in MM diagnosis

August 1, 2007

Diagnosing malignant melanoma early is key to a better prognosis. A recent study shows that the use of reflectance-mode confocal microscopy in pigmented lesions can greatly increase diagnostic specificity, and can aid the physician in diagnosing malignant melanomas early.

Modena, Italy - The incidence of malignant melanoma (MM) has more than tripled in the white population in the last 20 years, and it is currently the seventh-most-common cancer in the United States.

Experts agree that early diagnosis and prompt surgical excision of cutaneous melanoma are key to reducing mortality rates. Dermoscopy has been proven to improve diagnostic accuracy, especially in thin melanomas. A recent study shows that the use of in vivo reflectance-mode confocal laser microscopy (RCM) can significantly improve melanoma diagnostic specificity, thereby allowing doctors to diagnose melanomas earlier, thus improving survival rates in patients.

"The recent introduction of the in vivo reflectance-mode confocal laser microscopy enables the physician to instantly visualize skin structures at a quasi-histopathologic resolution. This novel technology represents a new noninvasive approach for the in vivo study of physiologic and pathologic conditions of the skin," says Giovanni Pellacani, M.D., of the department of dermatology at the University of Modena and Reggio Emilia, Modena, Italy.

Dr. Pellacani conducted a study using the RCM to evaluate the frequency of confocal features in benign and malignant melanocytic lesions and their diagnostic significance for MM identification.

The study included 102 consecutive melanocytic lesions taken with the RCM. Of the total number of cases taken, 37 were MMs, 49 were acquired nevi (21 junctional, 27 compound and one intradermal) and 16 were epithelioid and/or spindle cell nevi. Approximately 163 images per lesion were evaluated. All malignant lesions were superficial spreading MMs with a mean Breslow thickness of 0.8 ± 0.77 mm.

Dr. Pellacani found that in the granulosum and spinosum layers, the melanocytic lesions were usually characterized by a honeycombed pattern, a cobblestone pattern or both.

"The presence of a disarranged pattern was specific for the diagnosis of MM, as it was seen in 40 percent of malignant lesions and in one Spitz nevus. Furthermore, pagetoid cells were observed in the majority of MMs and in less than 11 percent of benign lesions, especially in Spitz nevi. The widespread distribution and extension of pagetoid cells to the stratum corneum was significantly correlated to malignancy," Dr. Pellacani tells Dermatology Times.

At the level of the basal cell layer and the dermoepidermal junction, Dr. Pellacani says the majority of the acquired nevi were characterized by edged papillae, as opposed to the non-edged papillae seen in approximately 95 percent of MMs and in 76 percent of Spitz/Reed nevi. At the basal layer, the MMs were characterized by larger and more irregular cells, compared with nevi.

"The presence of marked cytologic atypia throughout the lesion witnessed in 56 percent of MMs and in less than 5 percent of benign lesions was seen as a specific marker of malignancy. Also, in approximately 65 percent of MMs and in only two benign lesions, the confocal reticular architecture, represented by lines of cells and dermal papillae, was occasionally interrupted by stretches of numerous irregularly shaped, highly reflective cells," Dr. Pellacani says.

In the papillary dermis, melanocytic clusters were seen in about 65 percent of lesions, and according to Dr. Pellacani, this corresponded very closely to the invasive MMs and compound melanocytic and Spitz/Reed nevi. He says isolated cells with an eccentric dark nucleus and bright cytoplasm seen within the dermal papillae were considered a specific marker for malignancy, as this was observed in 45.5 percent of invasive MMs and only in two benign lesions.

"RCM offers the possibility to noninvasively investigate the cytological and architectural aspects of clinically difficult lesions, as it shows features reported as suggestive of MM diagnosis and substrates of characteristic dermoscopic patterns, such as pigment network and globules. Because light source limits the depth of penetration to approximately 200 to 300 micrometers, permitting the characterization of superficially located structures and cells, this technique seems to be particularly suitable for differentiation between flat to palpable pigmented lesions with atypical features at dermoscopic observation," he says.

Diagnostic model

Dr. Pellacani designed a diagnostic model that requires the identification of six features that independently correlate with the diagnosis of MM.

When using this algorithm model and considering the presence of at least two features (one major and one minor criterion) essential for MM diagnosis, Dr. Pellacani was able to correctly diagnose all MMs except for one, as well as 47 of 65 benign lesions.