Benign Acral Junctional Naevus (BAJN)
Author: Dr Annie Price
Chief Editor: Dr Daniel Keith
This common naevus refers to a benign proliferation of melanocytes. Classically, they appear as brown/black macules or papules which are well circumscribed. Atypical BAJN may have varying shades of colour; poor demarcation; with multiple morphologies. Dermoscopy is a particularly useful clinical adjunct for atypical melanocytic naevi.
BAJN typically occur on the palms of the hands and the soles of the feet. They can also be found on the volar surface of the fingers and toes.
Most cases of BAJN arise de novo and progression to acral melanoma is rare.
Macroscopic Appearance
Figure 1.
A BAJN on the palmar surface of the hand. A multi-pigmented, brown macule with a characteristic lattice-like pattern.
Dermoscopic Appearance
BAJN have three characteristic dermoscopic findings.
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Parallel furrow pattern is regarded as the hallmark dermoscopic sign of BAJN. Melanocytes are arranged in nests beneath the surface furrows. These nests subsequently form melanin columns in the cornified layer of the epidermal surface, creating a parallel pattern.
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Lattice-like pattern (see Figure 2). This is a variant of the parallel furrow pattern in which the pigmentation crosses the ridges to form a net-like appearance.
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Fibrillar pattern refers to the oblique arrangement of melanin columns (created during the parallel furrow stage). This is the result of a mechanical force so are seen commonly on pressure areas of the foot.
Figure 2.
Lattice-like pattern in BAJN. The yellow arrows show the vertical and horizontal arrangement of pigmentation in the furrows of the stratum corneum.
Figure 2.
Unannotated image
Figure 3.
A further dermoscopic image of an acral naevus showing the globular variant of the parallel furrow pattern.
Image courtesy of Sister Jo Jenkins, Advanced Nurse Practitioner, Primary Care.
