A biopsy is taken from a well-circumscribed tan-brown macule on sun-exposed skin of a 50-year-old man. Histology shows elongation of rete ridges, an increased number of melanocytes along the basal layer, and epidermal melanin deposition. Which clinical lesion does this describe?

• A Ephelis (freckle)
• B Café-au-lait macule
• C Junctional melanocytic naevus
• D Lentigo simplex ✓

Explanation

A lentigo shows elongated rete ridges with an increased number of solitary melanocytes along the basal layer, distinguishing it from an ephelis, in which the number of melanocytes is normal and only melanin production increases after sun exposure; ephelides also fade in winter while lentigines persist. Junctional naevi show nests of melanocytes rather than solitary cells. Café-au-lait macules show giant melanosomes and normal melanocyte numbers with no rete ridge elongation.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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