Derm Dx: A large mass on the scalp

A 40-year-old African American man presents for evaluation of a mass affecting his posterior scalp, which has enlarged in size during the past 3 to 4 years. The growth is asymptomatic. Examination reveals a soft and somewhat movable nodule that is nontender to palpation. Keloidal papules are noted on his lower scalp. No other masses are found elsewhere.