Reflectance Confocal Microscopy and Electrical Impedance Spectroscopy in the Early Detection of Melanoma in Changing Lesions during Long-term Follow-up of Very High-risk Patients

Abstract

Electrical impedance spectroscopy has clinical relevance in diagnosing malignancy in melanocytic lesions. Sixty-eight lesions with changes during digital follow-up of patients at very high risk of developing melanoma were prospectively included in this study from February to December 2016. Electrical impedance spectroscopy and reflectance confocal microscopy were performed to evaluate their performance in this subset of difficult lesions. Forty-six lesions were considered suspicious on reflectance confocal microscopy and were excised, of these, 19 were diagnosed as melanoma. Fifteen melanomas were detected by electrical impedance spectroscopy, while 4 received a score lower than 4, which suggested no malignancy. The addition of reflectance confocal microscopy improves accuracy while maintaining the same sensitivity. In the case of electrical impedance spectroscopy scores <4, lesions exhibiting changes in follow-up may need short-term monitoring or excision if dermoscopy shows criteria for melanoma. Results of electrical impedance spectroscopy in this subset of very early lesions should be carefully considered due to the risk of false negatives.

Fig. 1

Dermoscopy of 4 melanomas with an electrical impedance spectroscopy score below 4. (A) Case 1. Asymmetrical melanocytic lesion with multicomponent pattern, an irregular light-brown network on the periphery of the lesion, dotted vessels in the centre of the lesion and an area with inverted network (total dermoscopy score (TDS) 4.7). (B) Case 2. Asymmetrical melanocytic lesion, with an irregular globular pattern: globules of different size and colour at the periphery and a papillomatous component in the centre of the lesion (TDS 5.1). (C) Case 3. Asymmetrical melanocytic lesion with an atypical hyperpigmented network (TDS 4.3). (D) Case 4. Asymmetrical melanocytic lesion with different shades of brown and a few irregular globules on the periphery (TDS 3.2).

Fig. 2

(A) Melanoma in situ (electrical impedance spectroscopy (EIS) <4) on the lower leg of a woman with atypical mole syndrome and personal and familial history of melanoma (5 mm diameter). (B and C) One-year digital dermoscopy follow-up of case 1. Asymmetrical melanocytic lesion with multicomponent pattern, irregular growth of the brown network at the periphery of the lesion can be appreciated after 1 year, persistent dotted vessels in the centre of the lesion and area with subtle inverted network. (D) Histopathological section of the lesion, melanoma arising on a naevus, single/isolated atypical melanocytic proliferation, continuous on suprapapillary areas and confluence of different sized nests. At dermal level, deep melanocytic proliferation (magnification × 10). (E) Detail of D. At greater magnification, isolated melanocytic proliferation with confluence in suprapapillary areas and pagetoid cells (magnification × 20).

Fig. 3

Reflectance confocal microscopy (RCM) in 2 of the melanomas from Fig. 1. (A) RCM at basal cell layer (case 3): atypical cobblestone and roundish and dendritic pagetoid infiltration of the epidermis. In the lower right part, presence of non-edged papillae (*). (B) RCM of a particular of A: disarranged honeycomb and dendritic pagetoid cells. (C) RCM VivaBlock^® at the junctional layer (case 2): presence of edged and non-edged papillae. Dense and dense/sparse nests with different refractivity. (D) RCM of a particular of C: cellular polymorphism inside the nests. Atypical hyper-refractile nucleated cells are visible (arrows).