What exactly does impedance spectroscopy measure?

How the tissue of a mole conducts and stores very weak electrical signals. Healthy and altered cells differ in size, shape, orientation, density and membrane structure, and this is reflected in the electrical impedance. From the impedance pattern measured, the classifier derives a value.

How should the value on the scale from 0 to 10 be read?

The value stands for the degree of cellular change measured: the higher it is, the more pronounced the change that was measured; a low value points to little change. What that means for your mole is something we discuss with you in the context of the other findings. The value on its own is not a diagnosis.

Does the examination hurt?

As a rule, no. The electrical impulses the sensor sends into the skin are so slight that usually all you feel is the sensor touching the skin. Nothing is cut and no blood is drawn.

How long does it take until the result is available?

The result is available within about 10 minutes and is then discussed with you.

Is the measurement possible during pregnancy and on dark skin?

Yes. Impedance spectroscopy can also be used during pregnancy. It can also be applied to more strongly pigmented skin, for example skin type IV (olive complexion, dark eyes and hair) and darker skin types, where many other diagnostic methods reach their limits.

Does the measurement replace removing a suspicious mole?

No. It provides an additional piece of information for the decision. If the suspicion persists or the value is conspicuous, we recommend removal with examination under the microscope; only that secures the diagnosis. Conversely, an unremarkable result together with the other findings can argue for monitoring a mole rather than removing it.

Impedance spectroscopy (Nevisense®)

If, after dermoscopy and ultrasound, it remains unclear whether a mole is benign, electrical impedance spectroscopy (Nevisense®) can provide an objective piece of additional information. The measurement draws no blood and is almost painless; as a rule, all you feel is the sensor touching the skin.

Overview

Despite computer-assisted image analysis (FotoFinder®) and 20-MHz ultrasound, with some moles and other skin tumours it remains uncertain whether they could be a malignant change or a precursor of one. For these cases we use electrical impedance spectroscopy (Nevisense®), an examination method developed at the Karolinska Institute in Stockholm that requires neither an incision nor a blood sample.

Healthy skin tissue differs from atypical, diseased tissue in the size, shape, orientation and density of its cells and in the structure of the cell membranes. These differences affect how the cells conduct and store electricity. The measurable property behind this is called electrical impedance. When a mole is examined with very weak electrical signals, the impedance pattern can reveal changes that may point to melanoma or non-melanoma skin cancer and their precursors.

The Nevisense® classifier reports the result as a value on a scale from 0 to 10. The value describes the degree of cellular change measured: the higher it is, the more pronounced the change that was measured. It is not a diagnosis in itself but an additional piece of information that we assess together with the clinical picture, dermoscopy and ultrasound. The aim is to avoid unnecessary removals wherever possible.

Areas of application

Moles and other skin tumours that remain unclear after dermoscopy (FotoFinder®) and 20-MHz ultrasound
Suspected precursors or early forms of melanoma (black skin cancer)
Suspected precursors or early forms of non-melanoma (light) skin cancer
Skin lesions on the face, where a scar can be particularly distressing
Skin lesions in body regions that tend to heal with poorer scars, for example in the breast area
A known tendency to poor scar healing
Assessment during pregnancy
More strongly pigmented skin (skin type IV and darker skin types), where other methods can reach their limits

Procedure

Placing the finding in context
First we assess the mole as usual: clinically, with digital dermoscopy (FotoFinder®) and, where needed, with 20-MHz ultrasound. If uncertainty remains after that, we suggest impedance spectroscopy as an additional measurement.
Measurement with the sensor
A sensor is placed on the mole and sends very weak electrical signals into the skin. They are so slight that, as a rule, all you feel is the sensor touching the skin. No anaesthetic is needed; nothing is cut and no blood is drawn.
Reading on the scale from 0 to 10
The device evaluates the impedance pattern measured and reports a value between 0 and 10. The higher the value, the more pronounced the cellular change measured. The result is available within about 10 minutes.
Deciding together
We discuss the value with you in the context of the other findings. From that it follows whether monitoring is sufficient or whether we recommend removal with examination under the microscope.

What to expect

The examination is almost painless; as a rule, all you feel is the sensor touching the skin.
It draws no blood and leaves no wound.
The result is available within about 10 minutes.
The measurement is also possible during pregnancy.
It can also be used on more strongly pigmented skin, for example skin type IV and darker skin types.
Impedance spectroscopy supplements dermoscopy and ultrasound; it does not replace them.
Impedance spectroscopy is as a rule a self-pay or IGeL service; we discuss the framework with you beforehand.

Risks & notes

The measurement itself is non-invasive and carries no notable risks.
No diagnostic method offers 100 per cent certainty. A low value does not rule out a malignant change in every case, and a high value does not prove one. The value is therefore always assessed together with the clinical picture.
If the result is conspicuous or the suspicion persists, surgical removal with examination under the microscope (histology) may be necessary; only that secures the diagnosis.
The device-assisted evaluation supports the medical decision and does not replace the doctor's assessment.
Not every skin lesion is suitable for the measurement; whether it makes sense in your case is something we clarify during the examination.

What the measurement is meant to achieve

Impedance spectroscopy is meant to put the decision for or against removal on a broader footing. The aims are:

an objective piece of additional information alongside the doctor's assessment
fewer removals of benign moles and thus fewer procedures
fewer scars, which matters especially on the face, in the breast area and with a known tendency to poor scar healing
detecting precursors and early forms of melanoma and non-melanoma skin cancer

Frequently asked questions

What exactly does impedance spectroscopy measure?: How the tissue of a mole conducts and stores very weak electrical signals. Healthy and altered cells differ in size, shape, orientation, density and membrane structure, and this is reflected in the electrical impedance. From the impedance pattern measured, the classifier derives a value.
How should the value on the scale from 0 to 10 be read?: The value stands for the degree of cellular change measured: the higher it is, the more pronounced the change that was measured; a low value points to little change. What that means for your mole is something we discuss with you in the context of the other findings. The value on its own is not a diagnosis.
Does the examination hurt?: As a rule, no. The electrical impulses the sensor sends into the skin are so slight that usually all you feel is the sensor touching the skin. Nothing is cut and no blood is drawn.
How long does it take until the result is available?: The result is available within about 10 minutes and is then discussed with you.
Is the measurement possible during pregnancy and on dark skin?: Yes. Impedance spectroscopy can also be used during pregnancy. It can also be applied to more strongly pigmented skin, for example skin type IV (olive complexion, dark eyes and hair) and darker skin types, where many other diagnostic methods reach their limits.
Does the measurement replace removing a suspicious mole?: No. It provides an additional piece of information for the decision. If the suspicion persists or the value is conspicuous, we recommend removal with examination under the microscope; only that secures the diagnosis. Conversely, an unremarkable result together with the other findings can argue for monitoring a mole rather than removing it.