Dermatology: Practical and Conceptual


Research  |  Dermatol Pract Concept 2016;6(4):1 1

DERMATOLOGY PRACTICAL & CONCEPTUAL
www.derm101.com

Evaluation of electrical impedance spectroscopy 
as an adjunct to dermoscopy in short-term 
monitoring of atypical melanocytic lesions

Hannah Ceder1, Alexandra Sjöholm Hylén1, Ann-Marie Wennberg Larkö1, John Paoli1

1 Department of Dermatology and Venereology, Sahlgrenska University Hospital and Institute of Clinical Sciences at the Sahlgrenska 

Academy, University of Gothenburg, Gothenburg, Sweden

Key words: dermoscopy, atypical melanocytic lesion, melanoma, short-term monitoring, electrical impedance spectroscopy

Citation: Ceder H, Sjöholm Hylén Alexandra. Wennberg Larkö, A-M, Paoli J. Evaluation of electrical impedance spectroscopy as an 
adjunct to dermoscopy in short-term monitoring of atypical melanocytic lesions. Dermatol Pract Concept 2016;6(4):1. doi: 10.5826/
dpc.0604a01

Received: June 29, 2016; Accepted: July 22, 2016; Published: October 31, 2016

Copyright: ©2016 Ceder et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, 
which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: None.

Competing interests: None to declare. SciBase AB, Stockholm, Sweden loaned the Nevisense® equipment and electrodes needed for the 
study to the Department of Dermatology at Sahlgrenska University Hospital, but the company had no influence on the study design nor 
data analysis.

All authors have contributed significantly to this publication.

Corresponding author: John Paoli, MD, Associate Professor, Department of Dermatology, Sahlgrenska University Hospital, 413 45 
Gothenburg, Sweden. T. +46730404044. Email: John.paoli@vgregion.se 

Background: Early detection of melanoma is vital for treatment outcome and survival. Short-term 
sequential digital dermoscopic monitoring (ST-SDDM) involves the capture and assessment of dermo-
scopic images of one or more atypical melanocytic lesions (AMLs), at baseline and after four months, 
in order to detect early morphologic changes. Electrical impedance spectroscopy (EIS) is a diagnostic 
tool with high sensitivity for the detection of malignant melanocytic lesions.

Objectives: The aim of this study was to assess whether EIS, in addition to ST-SDDM, could improve 
the selection of AMLs requiring surgery.

Methods: In this retrospective descriptive study, 22 AMLs in 19 patients were monitored with both 
ST-SDDM and EIS. A modified EIS decision-making algorithm was established. AMLs were excised 
if any dermoscopic changes were seen and/or if the EIS score had increased significantly at follow-up. 
Statistical analyses were made including sensitivity, specificity, PPV and NPV.

Results: A total of seven lesions (32%) were excised. Four lesions (57%) were excised solely because 
of dermoscopic changes including a 0.4 mm-thick melanoma and three benign nevi. Three benign le-
sions (43%) were excised because of increased EIS scores without any dermoscopic changes. The EIS 
scores at follow-up showed high variability as compared to the initial scores.

Conclusion: The addition of EIS to ST-SDDM did not identify additional malignant lesions. There 
was no correlation between dermoscopic changes seen with ST-SDDM and increased EIS scores. Three 
histopathologically benign lesions were needlessly excised. Moreover, the low reproducibility and the 
possible interoperator variability of the method raised concerns.

ABSTRACT



2 Research  |  Dermatol Pract Concept 2016;6(4):1

values (PPVs) as shown in Table 1 [6,7]. EIS is approved for 

clinical use, but how the EIS score should be interpreted and 

used in clinical practice is still unclear.

At the Department of Dermatology, Sahlgrenska Univer-

sity Hospital, the combination of clinical examination and 

ST-SDDM after four months has been used in the assessment 

of AMLs requiring follow-up to determine whether they 

should be surgically removed or not.

Objectives

The objective of this study was to assess whether EIS in addi-

tion to conventional practice (ST-SDDM) could improve the 

selection of patients with AMLs needing surgery. The sec-

ondary objective was to determine the correlation between 

dermoscopic changes and EIS scores during short-term moni-

toring of AMLs.

Methods

In February 2015, EIS was introduced into clinical practice 

in combination with ST-SDDM at the Department of Derma-

tology, Sahlgrenska University Hospital. In this retrospective 

descriptive study, the clinical outcome of all patients with 

AMLs that were followed with ST-SDDM combined with 

EIS measurements during the period from February 1 to June 

30, 2015, were analyzed. The Regional Ethical Review Board 

assessed the study as a retrospective appraisal of quality of 

care and therefore had no objections to the study.

All patients over the age of 18 years diagnosed with 

an AML and monitored with ST-SDDM and EIS during 

the study period were considered eligible. Patients lost to 

follow-up, not meeting EIS measurement criteria (see below), 

having insufficient patient notes or with dermoscopic images 

of poor quality were excluded. Certain criteria must be met 

for EIS measurements to be valid. The lesion must have a 

Background

The concept of an atypical melanocytic lesion (AML) can be 

applied to any pigmented lesion in which the clinical and der-

moscopic criteria are sufficient to classify it as melanocytic, 

but are insufficient to determine whether the lesion is a benign 

nevus or an early stage of melanoma. When patients pres-

ent with one or more AMLs, excision for histopathological 

diagnosis may be necessary, but more advanced non-invasive 

diagnostic methods might be preferred.

Dermoscopy is a technique that uses a handheld magnify-

ing device combined with either the application of immersion 

fluid between the transparent plate of the device and the skin 

or the use of cross-polarized light. This technique allows for 

visualization of diagnostic features of skin lesions not visible 

to the naked eye. It is a tool that helps the clinician to assess 

and differentiate between melanocytic and non-melanocytic 

lesions and determine whether they are benign or malig-

nant. Several diagnostic algorithms can be used (e.g., pattern 

analysis, 7-point checklist, ABCD, Menzies’ scoring method) 

[1,2]. Although dermoscopy is a very good complement to 

clinical evaluation, there will always be some lesions that lead 

to diagnostic uncertainty. To be able to identify and monitor 

these lesions without unnecessary excision, the use of short-

term sequential digital dermoscopic monitoring (ST-SDDM) 

is valuable [3].

Sequential digital dermoscopic monitoring (SDDM) 

involves the capture and assessment of successive dermo-

scopic images of one or more AMLs separated by a specific 

time interval. SDDM is performed in two settings: long-

term monitoring (LT-SDDM), where multiple AMLs are fol-

lowed during regular surveillance periods (usually every 6-12 

months) [4], and short-term monitoring (ST-SDDM), where 

one or a few AMLs are re-examined only once after a shorter 

surveillance period (3-4.5 months) [3]. Clinicians may choose 

to perform ST-SDDM of an AML based on slightly suspicious 

morphologic features observed during dermoscopy during a 

first visit or based on a worrisome patient history although 

the dermoscopic features of the AML appear to be benign.

Nevisense® (SciBase AB, Stockholm, Sweden) is a diag-

nostic tool based on electrical impedance spectroscopy (EIS) 

[5-7]. It measures tissue resistance by administering alternat-

ing electrical currents at various frequencies to the skin. Nor-

mal and abnormal tissue differ with regard to cell size, shape, 

density and structure of cell membranes. These different 

properties influence the ability of the tissue to conduct and 

store electricity and can influence the results of an EIS mea-

surement [5]. Previous studies have resulted in an algorithm 

in which EIS scores in the range of 0-3 in the Nevisense® 

system represent a negative predictive value (NPV, i.e., the 

probability that the lesion is not a melanoma) of 98%, and 

scores of 4-10 represent steadily increasing positive predictive 

TABLE 1. Negative and positive predictive 
values for EIS measurements according 

to previous study [14].

EIS Predictive Value

0-3 98% (NPV*)

4 9% (PPV*)

5 13% (PPV*)

6 18% (PPV*)

7 22% (PPV*)

8 39% (PPV*)

9 51% (PPV*)

10 64% (PPV*)

* NPV, negative predictive value; PPV, positive predictive value.



Research  |  Dermatol Pract Concept 2016;6(4):1 3

how EIS measurements are performed have been published 

earlier [6,7].

Since the specificity and the positive predictive value of 

EIS measurements from previous studies were considered 

too low to be clinically applicable, the authors suggested a 

novel algorithm for the clinical management based on the 

EIS score. A greater emphasis was placed on the clinical and 

dermoscopic evaluation of lesions than on the EIS scores. The 

patients returned after four months for a follow-up visit dur-

ing which new clinical and dermoscopic images were taken 

and Nevisense® measurements were performed. The pres-

ence or absence of dermoscopic changes were visualized by 

comparing the two dermoscopic images on a digital monitor.

The management algorithm is presented in Figure 1. If the 

EIS score at visit 1 was 9 or 10, the lesion was excised regard-

less of the dermoscopic assessment. Otherwise, the AML(s) 

were followed up after four months. At follow-up, the dermo-

scopic images from both visits were compared. If dermoscopic 

changes were observed (e.g., growing or thickened network, 

new or bigger globules, new or growing negative network), 

the lesion was excised regardless of the EIS score at visit 2. 

Figures 2-3 show examples of AMLs with absence and pres-

ence of dermoscopic changes, respectively. If no dermoscopic 

changes were observed after four months, the EIS score deter-

mined the management decision. If the EIS score at visit 1 was 

0-6 and had not increased by more than 1 point at follow-up 

or if the EIS score at visit 1 was 7-8 and had not increased at 

all after four months, the AML was determined to be a benign 

nevus. Larger increases in the EIS score were interpreted as a 

possible sign of evolving malignancy and prompted excision.

Statistical analyses were made to determine the sensitivity, 

specificity, PPV and NPV of the method.

Results

A total of 19 patients (12 women and 7 men) with 22 AMLs 

were examined with both ST-SDDM and EIS during the 

study period (Table 2). The short-term interval between visits 

ranged from 3.5-4 months. The median age of the patients 

was 53 years (range 23 to 69 years).

diameter of 2-20 mm, the skin must be intact (i.e., lesions are 

not ulcerated or bleeding), and the lesion should be free of 

scars or fibrosis and located in skin areas free from eczema, 

psoriasis, acute sunburn or terminal hair. Furthermore, the 

lesion should not be located in specific anatomical areas, such 

as acral skin, genitals, eyes or mucous membranes.

After a full-body skin examination, the physician decided 

which suspected AML(s) should be followed using ST-SDDM 

and EIS. First, a clinical and a dermoscopic image were taken 

with a Canon Digital Camera PowerShot G12, G15 or G16 

(Canon, Tokyo, Japan) and the dermoscopy device Derm-

Lite FOTO® (3Gen; Dermlite®, San Juan Capistrano, CA, 

USA) attached to the camera. A 70% solution of isopropyl 

alcohol in water was used as immersion fluid when acquir-

ing the dermoscopic images. All images were stored in the 

patient’s electronic journal. Subsequently, an EIS measure-

ment was carried out by one of 

two certified users (HC and ASH) 

with the Nevisense® instrument, 

which is equipped with a probe 

and a disposable five-bar electrode 

with an area of 5 x 5 mm. The sys-

tem measures bio-impedance of 

the skin at 35 different frequen-

cies, logarithmically distributed 

from 1.0 kHz to 2.5 MHz, at four 

different depths utilizing 10 per-

mutations. More exact details on 

Figure 1. Management algorithm. [Copyright: ©2016 Ceder et al.]

Figure 2. Atypical melanocytic lesion without dermoscopic changes after ST-SDDM. The EIS score 

was 8 at day 0 (left) and 6 at the follow-up visit (right). [Copyright: ©2016 Ceder et al.]



4 Research  |  Dermatol Pract Concept 2016;6(4):1

In 10 cases (45%), the difference in EIS 

scores was ≥2 points and differences up 

to ± 4 points were observed.

If the algorithm provided by the 

manufacturer had been followed, 19 

AMLs would have been considered sus-

picious and excised. Of these, only one 

was malignant. Thus, in this very lim-

ited sample, and assuming that the non-

excised lesions were correctly diagnosed 

using ST-SDDM, the positive predictive 

value (PPV) of EIS alone was 5.3% and 

the specificity was 14.3%. The sensitiv-

ity and negative predictive value (NPV) 

were both 100%.

Conclusions

Melanoma affects more than 3700 

people in Sweden each year. After non-

melanoma skin cancer, malignant mela-

noma is the cancer type whose incidence 

A total of seven lesions (32%) were 

excised. Upon histopathological exami-

nation, four were dysplastic nevi, two 

were compound nevi and one was a 

thin superficial spreading melanoma 

with a Breslow thickness of 0.4 mm 

without ulceration (Figure 3). Four of 

the seven excised lesions (57%) were 

excised solely because of dermoscopic 

changes. In these cases, the EIS score 

was reduced by 2 points at follow-up 

in two lesions and unchanged in the 

other two. Three of the seven excised 

lesions (43%) were excised because of 

changes in the EIS score without any 

dermoscopic changes. These were all 

histopathologically benign. None of 

the seven excised lesions showed both 

dermoscopic changes and a significantly 

increased EIS score at follow-up.

The EIS scores at day 0 and at fol-

low-up showed a rather high variability. 

Figure 3. Atypical melanocytic lesion with dermoscopic changes between the baseline visit 

(A and C) and follow-up (B and D). The EIS score was 7 at baseline and 5 at follow-up four 

months later. The lesion diameter had increased (A➝ B) and several brown globules within 

a negative network had increased in size (circled areas in C and D). Histopathologically, this 

atypical melanocytic lesion was confirmed as a superficial spreading melanoma. [Copyright: 

©2016 Ceder et al.]

is increasing most in Sweden [8]. Mela-

noma detection often poses a challenge 

in equivocal lesions or in patients with 

many AMLs. As early detection of mela-

noma is vital for treatment outcome 

and survival [9,10], additional objective 

information that could assist the clini-

cian in obtaining a correct diagnosis and 

in deciding whether to excise the AML 

or not is desirable. The attempt in this 

study to use the EIS score algorithm to 

complement ST-SDDM did not seem to 

provide any additional help. Firstly, the 

evaluated algorithm did not identify 

additional malignant lesions. Further-

more, three histopathologically benign 

lesions were needlessly excised because 

of changes in the EIS score without any 

dermoscopic changes. These lesions 

would have been acquitted using only 

ST-SDDM. Moreover, the discrepancies 

between EIS scores over time were con-

siderable in several cases, which raised 

concerns about the reproducibility and 

the possible interoperator variability 

of the method. Changes in EIS scores 

alone did not appear to correlate with 

malignancy. For example, a consider-

able increase of 2-4 EIS points between 

measurements did not correlate with 

histopathological malignancy, and it is 

difficult to interpret the meaning of a 

decrease of the EIS score by 4 points 

in a dermoscopically unchanged lesion. 

Lastly, none of the lesions showing der-

moscopic change had an increased EIS 

score at follow-up, which further under-

mines the confidence in the measure-

ment reliability.

According to the company that pro-

duces the Nevisense® instrument, the dis-

crepancies between the EIS scores could 

depend on the use of different operators 

that may result in different reference 

measurement quality at the first visit 

and at follow-up. Another explanation 

may be the size of the lesion. The bigger 

the lesion is, the more measurements 

are required for each lesion, which may 

lead to errors.

There are several limitations to this 

study. The study was retrospectively 



Research  |  Dermatol Pract Concept 2016;6(4):1 5

additional techniques could perhaps increase the specificity 

when analyzing AMLs. For example, a study on the combina-

tion of EIS with near-infrared (NIR) spectroscopy for analyz-

ing melanocytic lesions provided a specificity of 95%, albeit 

with a lower sensitivity of 83% [11].

Regarding the term AML that we use in this study, we 

propose that this term should replace the incorrectly used 

term of a clinically suspected “dysplastic nevus” which is 

unfortunately used by too many dermatologists today. A 

“dysplastic” nevus is a variant of a benign melanocytic nevus, 

which can only be diagnosed histopathologically with typical 

architectural disorder and varying degrees of nuclear atypia 

in intraepidermal melanocytes [12,13]. Between 2-18% of 

the population in Sweden have melanocytic lesions with a 

clinical suspicion of dysplastic nevus [14]. Nevertheless, the 

exact prevalence of dysplastic nevi is unknown since the 

clinicopathological correlation between clinical atypia and 

designed and the sample size was small. The evaluation con-

cerned EIS in conjunction with ST-SDDM, but ST-SDDM was 

at the same time used as the gold standard for diagnosis in 

non-excised lesions. A histopathological diagnosis of all the 

lesions would perhaps have allowed for a more certain evalu-

ation, but was not considered ethical to carry out.

This is the first independent study, to our knowledge, in 

which EIS measurements have been carried out on the same 

melanocytic lesion at two different points in time to test 

reproducibility. Further studies on the reproducibility and 

interoperator reliability of EIS are needed before conclusions 

can be made.

EIS measurements on AMLs showed lower specificity 

compared with previous studies on EIS [5-7]. This may be 

due to the fact that the inclusion criteria in this study were 

different and that the sample size was smaller. Consequently, 

the studies cannot be directly compared. EIS combined with 

TABLE 2. Demographic data of all patients and clinical/histopathological characteristics of all 
atypical melanocytic lesions. [Copyright: ©2016 Ceder et al.]

Lesion Sex* Age Location
Size? 
(mm)

EIS-
score 
day 0

EIS-
score 

follow-
up

EIS score 
difference

Dermoscopic 
change

Treatment Histopathology

1 M 64 Back 7x7 5 7 +2 No Excision
Dysplastic nevus, moderate 
dysplasia

2 F 26 Abdomen 6x4 6 7 +1 No None -

3 M 37 Back 8x4 8 6 -2 No None -

4 M 41 Stomach 6x5 4 3 -1 No None -

5 F 24 Thorax 6x5 5 6 +1 No None -

6 F 60 Abdomen 14x12 7 5 -2 Yes Excision SSM, 0.4 mm

7 F 51 Gluteus 7x6 4 5 +1 No None -

8 F 66 Arm 2x3 5 3 -2 Yes Excision Compound nevus, inflamed

9 F 66 Back 7x5 8 5 -3 No None -

10 F 27 Back 10x11 3 7 +4 No Excision
Dysplastic nevus, moderate 
dysplasia

11 M 66 Back 9x6 5 5 0 Yes Excision
Dysplastic nevus, mild 
dysplasia

12 M 66 Abdomen 8x6 5 9 +4 No Excision
Dysplastic nevus, mild 
dysplasia

13 F 69 Back 8x7 5 3 -2 No None -

14 F 28 Leg 6x7 7 7 0 No None -

15 F 56 Pubis 9x7 6 6 0 No None -

16 M 67 Leg 3x4 2 2 0 No None -

17 M 67 Leg 7x4 4 4 0 No None -

18 F 23 Head 3x3 4 1 -3 No None -

19 F 53 Leg 6x4 6 2 -4 No None -

20 F 36 Back 6x5 6 6 0 Yes Excision
Compound nevus, strongly 
pigmented

21 M 24 Back 7x4 2 3 +1 No None -

22 M 53 Back 10x11 5 6 +1 No None -

* M, male; F, female; * Size, maximum x minimum diameter in mm.



6 Research  |  Dermatol Pract Concept 2016;6(4):1

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histopathological dysplasia in melanocytic nevi is very poor 

[14-17]. Hence, the term “dysplastic nevus” is not a clinical 

diagnosis and should be abandoned [18]. If the clinical diag-

nosis of a melanocytic lesion is uncertain, the lesion should 

therefore be called an AML until the diagnosis is confirmed 

clinically with ST-SDDM or histopathologically after a com-

plete excision of the lesion.

In this pilot study, the addition of EIS to ST-SDDM using a 

modified EIS algorithm did not identify additional pathologi-

cal lesions. Instead, some histopathologically benign lesions 

were needlessly excised. In addition, there was no correlation 

between dermoscopic changes seen with ST-SDDM and sig-

nificantly increased EIS scores. Also, the reproducibility of the 

EIS measurements was lower than expected, which is an issue 

that needs to be studied further before continuing to use this 

method in routine care. For now, we can therefore not recom-

mend EIS in the standard management of monitoring AMLs.

Acknowledgements

We would like to thank SciBase AB, Stockholm, Sweden for 

loaning us the Nevisense® equipment and electrodes needed 

to carry out this study.

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