Naevus Spilus

Naevus spilus (speckled lentiginous naevus) is a light brown patch, usually present from birth or early childhood, within which smaller, darker macules or papules appear over time.

It occurs in 1 to 2% of adults, and men and women are equally affected. The background patch is usually 1 to 20 cm, and the speckles appear after the first years of life. A segmental form follows a pattern of mosaicism.

Melanoma has been reported within the darker spots, though the risk is very small. Naevus spilus can be a feature of phacomatosis pigmentovascularis and of other mosaic syndromes.

Pathophysiology.

Post-zygotic activating variants of HRAS and BRAF have been found in the speckled lesions, and the background patch is a lentiginous melanocytic proliferation. The speckles are junctional or compound naevi.

• A tan to light brown patch with scattered dark brown macules (lentiginous) or raised papules (papular type), commonly on the trunk or limbs.
• Increasing number of speckles during childhood, usually without symptoms.
• Rarely, a segmental distribution, or association with a neurological, vascular or other mosaic feature (phacomatosis pigmentovascularis).

Red flags.

• A speckle that grows quickly, changes colour, ulcerates or bleeds.
• Neurological signs or a vascular malformation in the same area.

• Clinical diagnosis. Dermoscopy of the background patch (a fine, regular, light brown network) and of each spot (a regular globular or reticular pattern).
• Digital photographs of the patch for follow up. Biopsy or excision of a changing speckle, with histology.

Differential diagnosis.

• Café-au-lait macule (no speckles), congenital melanocytic naevus and Becker naevus.
• Lentigines, segmental neurofibromatosis and mosaic lentiginosis.
• Melanoma arising in a naevus.

• Reassure the patient. Excision of the whole patch is not needed.
• Examine and photograph the patch every year, teach the patient to look for change in any single speckle, and remove changing speckles with histology.
• Sun protection.
• Q-switched lasers can lighten the background but do not remove the speckles reliably.

Monitoring. Yearly skin check with photographs.

Referral and escalation. Dermatology for a changing lesion; urgent referral if melanoma is suspected.