Examination of a pigmented skin lesion near the hairline
It is known that acquired melanocytic naevi are not expected on the head and neck.1-3
Congenital-type naevi are commonly seen at this location, being raised naevi that often exhibit terminal hairs as a clue to their hamartomatous origin.
These naevi have a characteristic clinical and dermatoscopic morphology but, because there are numerous subtle variations, dermatoscopists are encouraged to deliberately examine these when encountered so as to become confident in diagnosing them.
Flat congenital-type naevi are also expected but they will be symmetrical in pattern and colour, will have a gradual border over the total periphery, and will have been present since the teen years.
A new flat lesion on the head or neck at mature age will have a differential diagnosis of solar lentigo/seborrhoeic keratosis or melanoma.
As a recent article1 concluded, “clinicians should always question a given histopathologic diagnosis of junctional nevus, dysplastic naevus or atypical lentiginous nevus from sun-damaged skin of the head/neck”.
Figure 1 (Click to expand)
A pigmented skin lesion on the neck does not have the dermatoscopic symmetry of a congenital-type naevus and has chaos including of border abruptness (abrupt at O18-20 and gradual elsewhere) with clues to malignancy of focal grey (K-L17-18) and polygons (J-K18-19).
Excision biopsy predictably discovered melanoma in situ.
A 55-year-old woman presented to her GP as a new patient complaining of chronic fatigue syndrome.
The GP noticed a pigmented skin lesion on her posterior neck adjacent to the hairline.
It did not have the expected clinical appearance of a congenital-type naevus, being flat and irregular in shape, so he requested permission to examine it dermatoscopically.
This discovered the lesion to be inconsistent with both a solar lentigo/seborrhoeic keratosis (it did not have a uniformly abrupt border) and a naevus (it was not symmetrical and did not have a uniformly gradual border).
In addition, there were clues to melanoma of grey colour and polygons (angulated lines).
Excision biopsy confirmed the diagnosis of melanoma in situ.
Associate Professor Cliff Rosendahl, Faculty of Medicine, University of Queensland.
Dr David Simpson, Peregian Springs Doctors, Peregian Springs, Qld.
References on request.