Clinical recognition

Usually presents as a solitary, sharply circumscribed, dark brown to black papule, plaque or verrucous nodule.
Most cutaneous lesions occur on trunk, head and neck or extremities in adults, often with the clinical feel of a seborrhoeic keratosis.
Surface may be waxy, stuck-on, papillomatous, crusted or irritated.
Rapid apparent change may reflect inflammation, trauma or new clinical recognition, but melanoma must be excluded if features are atypical.
Oral melanoacanthoma is a separate reactive mucosal melanocytic proliferation, typically on buccal mucosa, and should not be managed as an ordinary cutaneous SK.

Dermoscopy

May show seborrhoeic-keratosis clues such as milia-like cysts, comedo-like openings, fissures/ridges and a sharply demarcated edge.
Heavy melanin can obscure classic SK structures and create a melanoma-like black, blue-black or variegated pattern.
Irritated lesions may show crust, haemorrhage and polymorphous vascularity.
Absence of reassuring SK features, asymmetry, atypical network, blue-white veil, irregular dots/globules or atypical vessels should prompt biopsy.
Do not rely on the label “melanoacanthoma” clinically unless histology or very secure dermoscopic features support it.

Acanthotic epithelial proliferation resembling seborrhoeic keratosis with increased dendritic melanocytes scattered through the lesion.
Pigment is often abundant within keratinocytes, melanocytes and melanophages.
There should be no invasive malignant melanocytic proliferation; immunohistochemistry can highlight the dendritic melanocyte population if needed.
Histology separates melanoacanthoma from melanoma, pigmented Bowen disease, pigmented BCC and collision tumours.
Clinicopathological correlation is important when a biopsy samples only part of a heterogeneous pigmented lesion.

If clinically typical and dermoscopically secure as a seborrhoeic keratosis variant, reassurance is appropriate.
If there is any melanoma concern, perform biopsy/excision rather than destructive treatment.
Shave excision, curettage or elliptical excision can be used depending on site, thickness and diagnostic need.
Once histologically confirmed, no oncological follow-up is required for a completely treated cutaneous melanoacanthoma.
For oral pigmented lesions, refer to oral medicine/maxillofacial or appropriate mucosal pathway if diagnosis is uncertain.

Melanoma, including nodular melanoma and melanoma arising near seborrhoeic keratosis.
Pigmented basal cell carcinoma and pigmented Bowen disease/SCC in situ.
Irritated seborrhoeic keratosis, dermatosis papulosa nigra and pigmented verruca.
Pigmented actinic keratosis or lichen planus-like keratosis.
Collision tumour: a benign SK-like lesion adjacent to or overlying a malignant tumour.