A 58-year-old man presented with the new onset of an asymptomatic papule on the left upper arm. His past medical history included a melanoma in situ, several basal cell carcinomas, and many actinic keratoses.
Key point: Although the lesion was only about 2.5 mm in greatest diameter, it was surmounted by a rough keratin scale and felt firm to the touch. Biopsy revealed a moderately well-differentiated squamous cell carcinoma invading the subcutaneous fat.
Treatment: Moh's surgery was performed; the final defect remaining after obtaining tumor-free margins was 2.6 cm, consistent with an aggressive neoplasm.
Note: It is often surprising how wide and how deep skin cancers have already spread, despite a relatively small-looking superficial component.
