What is the cause of this patch?

This 86-year-old male presented for evaluation of a 6-month history of a 4 cm patch on his arm.

What is the cause?

A.Actinic keratosis.

B.Tinea corporis.

C.Squamous cell carcinoma.

D.Porokeratosis. 

E.Lichenoid keratosis.

(Answer and discussion on next page)

ANSWER—Actinic keratosis (by biopsy)

It is not unreasonable to biopsy this lesion which has an unusual appearance and presentation. Tinea would be expected to have a more scale (this lesion appears hyperkeratotic by comparison) with a slightly raised border. A squamous cell carcinoma in situ could appear like this. Porokeratoses should have a recognizable border that is palpable. Lichenoid keratoses should have recognizable features of a seborrheic keratoses. 

Treatment options include: 

• Cryosurgery.

• 5-fluorouracil (5% or 0.5%).

• Imiquimod.

• Solaraze (diclofenac).

• Picato.

David L. Kaplan, MD, is clinical assistant professor of dermatology at the University of Missouri, Kansas, City School of Medicine and at the
University of Kansas School of Medicine. He practices adult and pediatric dermatology in Overland Park, KS.