This 80-year-old man has been complaining to health care providers about the asymptomatic lesion on his right forearm for at least 5 years—“maybe more,” he says. During that time, he has been given a variety of diagnoses, mostly “infection” of some sort, along with prescriptions for oral antibiotics (cephalexin, trimethoprim/sulfa), topical antibiotics (mupirocin, triple-antibiotic cream), and germicidal washes (povidone and others). None of these treatment attempts has achieved results.
Prior to now, there has been no referral to dermatology, nor has any provider suggested biopsy of the lesion. The patient has a history of skin cancer (basal cell or squamous cell carcinomas) on his face, back, and arms. These followed a lifetime of sun exposure due to his work in construction and roofing.
The lesion in question is located on the dorsal aspect of his mid right forearm. Measuring almost 4 cm in aggregate, the lesion is composed of 2 adjacent bright red half-moon friable nodules in a circular configuration. There is almost no erythema or edema in or around the lesion, which is neither warm nor tender to touch.
There are no palpable nodes in the adjacent epitrochlear or axillary nodal locations.
The surrounding skin of this arm, as well as that of the opposite arm, is quite thin, discolored, and scaly and is covered with stellate scars. Examination of all other sun-exposed areas reveals similar changes but no other notable lesions.
What’s the diagnosis?