New test exposes dangerous moles

Most moles are harmless, and non-cancerous. Unfortunately, however, there are exceptions, and the mole turns cancerous. In such cases, it is important to act fast to prevent the disease from spreading.

One of the questions doctors need to address in such situations is: How dangerous are the cancer cells in this specific mole? This is an important question because the answer will determine how aggressively the doctors will treat the skin cancer, also called malignant melanoma.

‘A rule of thumb is that the thicker the malignant melanoma, the more dangerous it is. But it can be difficult to judge the severity of malignant melanomas if they’re more than one millimetre in thickness,’ says Beatrice Dyring-Andersen, doctor and PhD at Gentofte Hospital and the Novo Nordisk Foundation Center for Protein Research at the University of Copenhagen.

However, oncologists now have a completely new tool for assessing the severity of malignant melanoma. This so-called prognostic marker was discovered by a team of researchers from Denmark, Australia and the USA.

Beatrice Dyring-Andersen – whose research is partially funded by the Lundbeck Foundation – is a member of this research team, and the discovery was recently published in the scientific journal Nature Cancer.

Counting T cells
How do you use this new method to assess whether a malignant melanoma should be classified as dangerous – or whether it is in all likelihood relatively harmless?

In principle, you do this by mapping the ratio between T cells and cancer cells in the tumour. T cells are specialised cells and are part of the body’s immune system. Among other things, T cells combat viruses and cancer cells. Therefore, when cancer occurs, for instance in connection with malignant melanoma, the tumour will be attacked by the body’s T cells.

‘One of the key questions has always been whether it’s good or bad that there are lots of T cells in the tumour,’ says Beatrice Dyring-Andersen.

‘This question has been much debated within cancer research circles in recent years, but it’s been impossible to answer. For this reason, assessments of the severity of a melanoma are often uncertain, and we can reduce this uncertainty considerably by using the new method. Our study shows that it’s good if there are lots of T cells present in the tumour. Actually, the ratio between T cells and cancer cells should preferably be at least 20/80, and if the percentage of T cells compared to cancer cells is greater than 20, protection is even better. This means that the body is actively seeking to destroy the cancer cells in the malignant melanoma.’

Personalised medicine
Although this new method for assessing the severity of malignant melanomas is not yet being used in Denmark, Beatrice Dyring-Andersen says that it will give rise to a number of considerations in the future with regard to treatment of these patients:

‘We could, for instance, consider whether in certain cases it would be relevant to stimulate the patient’s own T cells medically to make them even more active. This new assessment we’re now able to make also points towards so-called personalised medicine, which means we can offer treatment more closely tailored to the individual patient and to his or her prerequisites for combating skin cancer to best effect,’ she says.

Cut into slices
In order to develop the test, the research team needed tumour samples from a large number of patients who had all been treated for malignant melanoma. And analyses of these samples – compared with details from anonymised journals about how the patients were fairing – provided the basis for the research.

Beatrice Dyring-Andersen explains that they studied tumour samples from a total of 200 patients, half from Denmark and half from Australia, and each sample was cast in a small block of paraffin to preserve it.

‘With the help of a special machine – in principle, a meat slicer – we were also able to cut ultra-thin slices of each individual sample. Using these slices, which were only 10/1000 of a millimetre thick, we could determine the ratio between the number of T cells and the number of cancer cells in the sample. By comparing the sample analyses with the data from the journals of the 200 patients, we were then able to establish that, in principle, the presence of many T cells in a malignant melanoma increases the probability that the tumour can be destroyed. This was how we reached our main conclusion,’ says Beatrice Dyring-Andersen.

Image text: Microscope image of one of the tumours studied by the researchers from Denmark, Australia and the USA. The green cells are cancer cells. The red and blue cells are T cells. The T cells are approximately 7/1000 of a millimetre in size.