A 69-year-old man presents to his primary care physician for a general checkup. The patient works as a farmer and gardens in his spare time. He has a medical history of poorly managed type 2 diabetes mellitus and irritable bowel syndrome. His current medications include lisinopril, metformin, insulin, fiber supplements, and a multivitamin. On physical exam, there is a calm, obese gentleman. Inspection of the patient's scalp reveals the finding shown in Figure A. The patient is sent home and instructed to keep a blood glucose journal. Three months later, the patient returns with his glucose journal. In addition, he complains of a cut on his scalp that is not seeming to heal. The patient's glucose journal reveals an average blood glucose of 175 mg/dL. His temperature is 98.8°F (37.1°C), blood pressure is 134/86 mmHg, pulse is 80/min, and respirations are 13/min. On inspection of the patient's scalp, the finding in Figure B is noted. Which of the following is the most likely diagnosis?
Basal cell carcinoma
Squamous cell carcinoma
Melanoma
Poor wound healing secondary to diabetes
Squamous cell carcinoma
This patient with a non-healing ulcer on the site of a previous actinic keratosis most likely has sustained progression of the lesion to squamous cell carcinoma.

Squamous cell carcinoma (SCC) is a common dermatological malignancy. Patients can present with actinic keratosis, which is a pre-malignant lesion in sun-exposed areas. These lesions can progress to squamous cell carcinoma if risk factors such as sun exposure continue. The presentation of SCC is typically an ulcerative lesion in a sun-exposed area. A biopsy will demonstrate atypical keratinocytes and malignant cells, invasion into the dermis, and keratin “pearls” on histology. Treatment is with wide local surgical excision with histologic confirmation of negative margins.

Waldman and Schmults present a review of the evidence regarding the epidemiology and treatment of squamous cell skin cancer. They discuss how the incidence of this disease continues to increase due to an aging population. They recommend local excision and treatment due to the risk of metastasis.

Figure/Illustration A is a clinical photograph demonstrating a rough scaly patch on the skin (red circle). This finding is consistent with actinic keratosis, which is a pre-malignant lesion typically found on sun-exposed areas.

Figure/Illustration B demonstrates an ulcerative lesion with wound formation on the skin (red circle). This finding is consistent with squamous cell carcinoma, a malignant lesion that can progress from actinic keratosis.

Incorrect Answers:
Answer A: Actinic keratosis represents a pre-malignant condition that this patient initially presented with (as demonstrated in Figure A). His current presentation reflects SCC, a progression from actinic keratosis given the new ulceration and non-healing wound.

Answer B: Basal cell carcinoma presents with a shiny or pearly appearance, rather than the ulcerative appearance that is seen in SCC. This disease should be treated with surgical excision.

Answer C: Melanoma presents with a pigmented lesion that has an irregular border, an uneven shape, and areas that differ in pigmentation. Patients with melanoma should undergo surgical staging as this disease can become metastatic and should be treated with surgical excision.

Answer D: Poor wound healing secondary to diabetes would be possible if there was a history of trauma to the scalp. The history of actinic keratosis and the current ulcerative lesion, point more toward a diagnosis of SCC. Non-healing wound in patients with diabetes are usually located on the foot rather than on the scalp.

Bullet Summary:
Actinic keratosis is a pre-malignant lesion that occurs in sun-exposed areas that can progress to squamous cell carcinoma.