What is the nodular lesion on this patient's leg?

CASE A 58-year-old man presented to the dermatology clinic with a 6-month history of a nodule on the pretibial part of his right leg. History The patient said that the lesion fi rst appeared a few days after he bumped his right shin against a table, lacerating the skin. A circular nodule subsequently emerged from the laceration and increased in size; the lesion was also painful, eventually prompting him to seek medical care. The pain was described as sharp in nature and was thought to be secondary to the lesion. He denied fevers, chills, or unintended weight loss. The patient did not apply anything to the area or seek other medical care before presenting to the clinic. He had no history of skin cancer. His medical history was otherwise noncontributory. He had no other known relevant family history. Physical examination A 1.3 cm (0.5 in) fi rm, erythematous tender nodule was present on the right anterior lower leg (Figure 1). No other notable lymphadenopathy or dermatologic fi ndings were observed during the patient’s visit.