Question:

A 20-year-old-lady presented with a hairy pigmented plaque on her right upper arm. The skin lesion was noticed since birth as a light brownish macule. The lesion darkened, increased gradually in size and thickness with hairs protruding from it. The skin lesion now measures 4.5 cm x 2 cm in size.

Answer: C. Congenital melanocytic naevus

Congenital melanocytic naevus is present from birth. It occurs in 1% of all newborn babies and persists throughout life. They are commonly between 1-5 cm in diameter, however they may vary greatly in size. They may be divided according to size into small (<1.5 cm), medium (1.5-20cm), and giant (>20cm in diameter). Giant pigmented hairy naevus is rare (<0.002% of infants), but may be so large as to cover the entire body like a bathing trunk, and accompanied by multiple smaller satellite congenital naevi on the limbs.

The malignant potential of congenital melanocytic naevus seems to be related to its size. There is significant risk of malignant melanoma for giant hairy pigmented naevus, with estimated lifetime risk of around 5%. The risk associated with medium to small congenital naevi has not been satisfactorily established, but appears to be very low given that malignant melanoma is uncommon, yet 1% of population has congenital melanocytic naevi.

Clinical features suggestive of malignant melanoma are changes in size, shape and colour. ABCDE stands for asymmetry of lesion, irregular border with satellite lesions, variation in colour, diameter >1 cm, and enlargement in size. Inflammation, bleeding, oozing, itch and pain may also be signs and symptoms indicating malignant transformation. Skin biopsy confirms the diagnosis.