Melanoma documented arising in an involuting naevus 3 years after cessation of monitoring

A 35-year-old female, with no family history of melanoma but with a personal history of three previous melanomas, presented for a routine skin examination in 2023. She had been treated for melanoma in situ on the right forearm at age 12, with subsequent primary invasive melanomas on the scalp at ages 21 and 26. Because of her categorisation as high risk, she was having 6-monthy whole-body skin examinations as well as sequential digital dermatoscopic imaging (SDDI) of multiple randomly selected skin lesions.

As part of this process one pigmented skin lesion over the upper thoracic spine (Figure 1, black arrow) was monitored annually from 2017 and as it was observed to become smaller, then stable on sequential images (Figure 2, 2017–2020), monitoring was suspended in 2020.

In 2023 at routine examination by the treating clinician, assisted by a qualified nurse-diagnostician, with active reference to total body photography (TBP) images, an observation was made by the nurse that the lesion previously monitored (Figure 1, black arrow) was now a similar size to a previously larger lesion below it (Figure 1, white arrow). A dermatoscopic image was taken and when compared with the previous image from 2020, significant progressive change in all quadrants was identified (Figure 2, 2023). The lesion was excised and submitted for histology, accompanied by relevant clinical information and dermatoscopic images. Histological examination was consistent with early melanoma in situ, with regression, arising in a pre-existing compound naevus (Figure S1). The subject patient has provided informed consent to the publication of their information contained within this manuscript.

Sequential digital dermatoscopic imaging of randomly selected multiple naevi has been shown to have diagnostic efficacy for patients at high risk of melanoma.¹ As well as facilitating diagnosis of early, and even featureless melanomas,¹ it has been demonstrated to improve specificity, avoiding excision of biologically indolent lesions.² It has been shown that monitoring may need to be continued long-term to detect slow-growing melanomas, in one large study major changes only being evident after a mean follow-up of 33 months.³ The use of TBP and SDDI, known as the ‘two-step method of digital follow-up’ has been suggested as an ideal surveillance strategy for high-risk melanoma patients.² It is also known that the provision of relevant clinical information has been shown to improve pathologists' confidence in, and accuracy of histological diagnosis.⁴

A meta-analysis of naevus-associated melanomas in 2017 reported that most cutaneous melanomas arose de novo, 29.1% arising in association with a naevus. In contrast to a commonly held misconception, melanoma-associated naevi were most frequently non-dysplastic, the bland dermal naevus being the most common type if congenital naevi were excluded.⁵

The current case illustrates a serendipitous outcome of the ‘two-step method of digital follow-up’, additionally facilitated by the deployment of university-trained, nurse-diagnosticians in the co-examination process.⁶ It also demonstrates the need to re-visit ‘finalised’ serial dermatoscopic imaging if subsequent clinical change is identified. While it cannot be determined definitively that the initially monitored lesion was benign, the documented sequence of events does support that hypothesis.

Cliff Rosendahl conceived and wrote the manuscript, Christine Lee, Sarah Coleman and Aksana Marozava were directly involved in the application of photographic technology and lesion detection and Blake O'Brien was the reporting dermatopathologist who also provided histology images. All authors critically reviewed and approved the manuscript.

The authors declare no conflict of interest to declare.