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Question: My son has a spot on his leg and we’re worried it might be melanoma skin cancer. It is flat, pigmented (brown) and about 4 millimeters in diameter with an irregular border. His physician is a very new doctor, just starting her practice. She suggested that it be removed using a punch biopsy and sent for testing. But we read on the website of the Canadian Cancer Society that a punch biopsy should not be done if the lesion is pigmented and there is a potential for melanoma because it might miss part of the spot. The excisional biopsy is preferred for melanoma. We also saw another website that said doing a biopsy may cause the cancer to spread. The doctor has told my son she does not think it is melanoma. But we don’t want to take any chances. If he asks for a referral to a specialist, it will lead to more delay. What should he do?
Answer: It’s understandable that you would be worried if there’s a possibility your son might have melanoma. Although it’s the least common of the three main types of skin cancer, it is the most deadly. If left untreated it has a tendency to spread to other parts of the body. So it’s important to catch it early.
I posed your question to two experts at Sunnybrook Health Sciences Centre: Dr. Neil Shear, head of dermatology; and Dr. Frances Wright, a cancer surgeon who specializes in melanoma (and breast cancer) cases.
First of all, both doctors say a biopsy cannot spread skin cancer regardless of whether the whole lesion is removed or not. This is one of the myths you can find on some Internet sites.
And, secondly, they agree your son needs to get an accurate diagnosis.
Melanoma has several distinctive characteristics that are often summed up by the so-called ABCDE rules:
- A is for Asymmetry. The lesion tends to be bigger on one side than the other. So, it is said to be asymmetrical.
- B is for border. It has an irregular or jagged border. A normal mole has a relatively smooth round or oval-shaped edge.
- C is for colour. Instead of the uniform brown colour of a normal mole, Melanoma may have many colours such as dark brown, black, red, blue and purple.
- D is for diameter. A normal mole is usually less than 5 millimetres in diameter. Melanoma may be significantly larger than 6mm.
- E is for evolving. A mole that changes in size, shape or appearance may be an indication of cancer. And if it begins to bleed or ooze, that’s usually not a good sign.
Even if a lesion has all these features, it may not be melanoma, says Dr. Shear. To make a definitive diagnosis, he says, the cells need to be looked at under a microscope. That means a biopsy must be performed to collect a tissue sample, which is then sent to a lab. It will be examined by a pathologist who is trained to tell the difference between normal and cancerous cells.
A punch biopsy is done using a round hollow cutting instrument, which is pushed down through layers of the skin into the underlying fat. A round core of tissue is removed.
The Cancer Society’s recommendation is partly based on the fact that some melanomas can be fairly large – greater than 5 mm in diameter. There is a risk that a punch biopsy may not get the entire spot and actually miss the cells that are cancerous. If that happens, the pathologist may not be able to make an accurate diagnosis. So it’s often recommended that a potential melanoma sample be collected by means of an “excisional” biopsy in which a scalpel is used to remove the entire area of abnormal skin, including a portion of normal skin if it’s technically possible. (A large biopsy on the face, for example, could be quite disfiguring so the approach used in each case needs to be evaluated separately.)
However, your son’s spot is relatively small – just 4 mm. Dr. Wright notes that punch-biopsy instruments come in a variety of sizes up to 6 millimetres in diameter. That means a punch biopsy should be able to remove the entire lesion.
If the pathologist determines that the spot is cancerous, then your son would need a follow-up procedure. A patch of skin 1 to 2 centimetres in diameter would be removed around the site of a melanoma just in case some cancerous cells have started to spread into the surrounding tissue. (Depending on the thickness of the melanoma, nearby lymph nodes may be also biopsied and examined for the presence of cancer cells. The results of those tests would help determine other courses of treatment.)
If your son is considering seeking a second opinion from a dermatologist or a surgeon with experience in melanoma cases, it will likely take some time to get an appointment. How long is it safe to wait? “It depends how long it has been sitting there and how aggressive it might be if it is a cancer,” says Dr. Shear. But, as a general rule, Dr. Wright adds, “waiting a few weeks or even a month won’t make a difference.”
Of course, before your son can see any specialist he would first need a referral from his family physician. So he needs to book another appointment with her.
That visit could provide an opportunity to have a full discussion about his concerns. He may also want to consider having his family doctor do the biopsy after all.
Based on your description of the spot, it sounds like a punch biopsy would remove the whole lesion so a pathologist could make an accurate assessment.
And, having a biopsy performed sooner rather than later, would eliminate the uncertainty about his condition. “It is better to have any type of biopsy rather than none and a significant delay,” says Dr. Wright.
Paul Taylor, Sunnybrook’s Patient Navigation Advisor, provides advice and answers questions from patients and their families, relying heavily on medical and health experts. His blog Personal Health Navigator is reprinted on Healthy Debate with the kind permission of Sunnybrook Health Sciences Centre. Email your questions to AskPaul@sunnybrook.ca and follow Paul on Twitter @epaultaylor