Deadly or benign?

Jun 01, 2007, 4:00am

It can be difficult to differentiate between Spitz nevi and melanoma lesions, and many times a definitive diagnosis is needed quickly. The confocal microscope and chromosome analysis technologies can help physicians significantly, but the need for quick response and the issue of availability of such devices still challenge physicians.

Key Points

Oklahoma City - Many experts agree that a central issue concerning Spitz nevi is the difficulty in differentiating them from melanomas.

Chromosomal painting techniques and novel technology, such as the confocal microscope, significantly help physicians distinguish between these two lesions, but the need to act quickly, coupled with the question of the availability of such devices, remain problematic, according to one specialist.

"If there is a doubt in the differentiation of a Spitz nevus from a melanoma, a sentinel node biopsy is sometimes recommended, since a lymph node metastasis implies a melanoma. This is one of the reasonable procedures you can do to help straighten out any ambiguities," says Mark F. Naylor, M.D., a dermatologist in Oklahoma City.

Chromosomal analysis

He says that one very helpful way to distinguish between these two lesions is to use chromosomal analysis or chromosomal painting technologies, if they are available.

Here, an examiner can see certain genetic changes that are characteristic of melanoma and indicate that the lesion in question is, in fact, a melanoma.

"It may be more expensive to do this procedure, but the real problem is that even if you have access to these sophisticated molecular technologies, the time scales that it takes for them to be completed are usually longer than the decision making time scale that you are working on," Dr. Naylor says.

Chromosomal painting can take several days to several weeks to complete, depending on whether the hospital is set up to do the procedure. The problem is that dermatologic surgeons do not have that much time when making critical, possibly life-saving decisions.

Confocal microscope

The confocal microscope is another option to help physicians differentiate between Spitz nevi and melanoma.

Characteristic histologic changes, such as the shot-gunning of abnormal melanocytes closer to the surface of the epidermis, can be seen easily with this microscope. The confocal microscope can give the physician rapid, same-day answers to questions on definitive diagnosis of a given lesion. The downside is that the microscope may not always be available.

Cost is an issue, as is technique, because the use of the device must be learned, Dr. Naylor says. The device has some limitations, as well.

"The confocal microscope does not show you the depth of the lesion because it can only go to a certain depth. The bottom of a lesion may be beyond the reach of the confocal microscope, and that is where it is most important to look.

"On the other hand, if you are lucky enough to see the shot-gunning of the surface epidermis, that would make you think about melanoma," Dr. Naylor says.

Clinical doubts

According to Dr. Naylor, these technologies assist diagnosis but, inevitably, some clinical doubts may still linger.

Physicians have to make clinical decisions based on partial information that leaves room for inaccuracy.

He says, in the end, it is better to err on the side of over-treating and admits that pediatric patients present more difficult cases, because no physician would perform surgery on a child if it can be avoided.

"The problem is that the melanomas in children can be just as aggressive as melanomas in adults. Even though it is not a common tumor in children, it is not rare. Also, Spitz nevi do occur more commonly in children. For those of us who see lots of children with pigmented lesions, this is a real issue," Dr. Naylor says.

The molecular technologies are the future for better discerning lesions, he says. More rapid genetic testing and better genetic markers that are relatively specific for melanoma are needed to help clinicians sort out a lesion that is clinically and histologically nebulous.

"If you know that there are chromosome losses or certain breaks on certain areas in the human genome of the chromosomes, those can be very suggestive for melanoma. So, if you can get that kind of information rapidly, it will certainly help you make decisions," Dr. Naylor says.