MEDizzy - A 65-year-old man who is a long-time farmer presents with a

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Reproductive Systems and Skin

A 65-year-old man who is a long-time farmer presents with a small, scaly erythematous lesion on the helix of his left ear. A biopsy from this lesion reveals marked degeneration of the dermal collagen (solar elastosis) along with atypia of the squamous epidermal cells. The atypia, however, does not involve the full thickness of the epidermis, and no invasion into the underlying tissue is seen. Which of the following is the most likely diagnosis?

ExplanationActinic (solar) keratoses, found on sun-damaged skin, microscopically show hyperkeratosis, parakeratosis, atypia of the epidermal keratinocytes, and degeneration of the elastic fibers in the dermis (referred to as solar elastosis). Clinically, actinic keratoses appear as irregular erythematous brown papules. When the atypia of the intraepidermal keratinocytes is extreme (full thickness), the lesion is referred to as Bowen disease (carcinoma in situ). Obviously in this lesion there is no invasion into the underlying dermis, which, if present, would be diagnostic of a squamous cell carcinoma. Keratoacanthoma, a benign tumor, may resemble squamous cell carcinoma both clinically and histologically, but penetration of the dermis never extends deeper than adjacent hair follicles. The lesion is cup-shaped with central keratin; biopsy or excision excludes squamous carcinoma.