Derm Dx: A growth behind the ear with straw-colored fluid

A 25-year-old woman presents for evaluation of a growth behind her right ear. The lesion was first noted several weeks ago and is asymptomatic but prone to trauma. Medical history is unremarkable. Examination reveals a 2.5-cm flesh-colored nodule that is semitranslucent and not freely movable. Puncture of the lesion produced straw-colored fluid.