Melanocytic vs. non-melanocytic: Two-step algorithm aids diagnosis

Jun 01, 2008, 4:00am

A two-step algorithm has been created to assist dermatologists in reaching definitive diagnoses of melanocytic and non-melanocytic lesions, tightening the noose on malignant melanoma and helping to catch these malignant lesions early.

Key Points

Barcelona, Spain - Recently, a team of dermatologists put together a two-step algorithm to assist dermatologists in recognizing different skin tumors, including malignant melanoma.

According to one specialist, dermatologists using this two-step algorithm can now increase the diagnostic accuracy of melanoma in about 25 percent of examinations done with the naked eye.

"The main reason for developing this two-step algorithm is because all of the criteria that have been described during these recent years want to discriminate between melanocytic and nonmelanocytic lesions, and try to search for specific criteria for pigmented and nonpigmented tumors that are so very common in our patients," says Joseph Malvehy, M.D., coordinator of the melanoma unit of the department of dermatology at the hospital clinic IDIBAPS, Barcelona, Spain.

The two-step method is the result of 20 years of experience from different study groups around the world, and was integrated in a consensus of the International Dermoscopy Society.

In the first step, the algorithm helps to discriminate between melanocytic lesions and BCC, seborrheic keratosis, dermatofibroma and vascular lesions.

In the second step, if the lesion is melanocytic, algorithms for the discrimination between different benign dysplastic nevi or melanoma are then applied.

These criteria are then used in a well-organized algorithm to reach a definitive diagnosis.

"Now we know much more about tumors, such as angiokeratoma and different adnexal tumors.

"We are even able to discriminate between different inflammatory diseases and infections of the skin using dermoscopy," Dr. Malvehy tells Dermatology Times.

With the application of these different criteria that have been described by pattern analysis, reaching a secure diagnosis is now much easier.

According to Dr. Malvehy, dermoscopy is very useful in the diagnosis of vascular tumors, as they can be immediately distinguished from other pigmented lesions. He says dermoscopy is a handy tool in the recognition and differentiation of the typical acquired angioma and angiokeratoma.

Dr. Malvehy says this is very important because angiokeratoma is, in part, very similar to melanoma, as these tumors are thrombosed and, therefore, appear black upon clinical examination. These tumors can now be recognized with great accuracy by dermoscopy using the criteria in these algorithms.

Dr. Malvehy says that in the first-step method, he evaluates the cutaneous tumors by dermoscopy and then determines if the tumor is melanocytic or if the tumor is none of the other tumors that he is able to recognize using the different criteria.

If nonspecific characteristics for the known cutaneous tumors are found in the dermoscopic examination, then this tumor could be a melanoma and should be removed.

"The most important point is that when you have a tumor in the skin without a clear diagnosis, you need to remove it. ... Every single tumor that exhibits nonspecific findings for the known criteria could be melanoma and should be removed," Dr. Malvehy says.