A 73-year-old woman presented with a rapidly growing, painful sore on her thigh. The lesion appeared spontaneously two weeks earlier without any identified triggers. It did not drain, bleed, or itch. The patient had no systemic symptoms, including fever, chills, or weight loss. She had a history of recurrent pus-filled boils that required incision and drainage.

Physical examination revealed a sharply demarcated, firm, erythematous lesion on her right, medial thigh that was nonfluctuant and had a punctate central plug (Figure 1). It was 0.7 × 0.6 cm in size and tender to palpation around the edges. Her vital signs were normal. A shave biopsy was performed.

Question

Based on the patient's history and physical examination findings, which one of the following is the most likely diagnosis?

• A. Cutaneous squamous cell carcinoma.

• B. Folliculitis.

• C. Keratoacanthoma.

• D. Nodular basal cell carcinoma.

• E. Skin abscess.

Discussion

The answer is A: cutaneous squamous cell carcinoma, which was confirmed on biopsy. Cutaneous squamous cell carcinoma is a malignant neoplasm of the skin that typically arises from actinic keratosis. Cutaneous squamous cell carcinoma classically presents as a firm, rapidly growing lesion that is the color of the surrounding skin or slightly erythematous. It can present as central ulceration or hyperkeratosis, as in this patient.¹ Smoking and exposure to ultraviolet radiation are predisposing factors. The head and neck are the most common locations for these lesions.² Evaluation of suspicious lesions should begin with a full-body inspection, followed by dermatoscopy and biopsy. Early detection and removal decrease the likelihood of metastasis and significantly improve prognosis.³