Pyoderma Faciale Female

A 26-year-old woman presents with a 2-week history of sudden, severe facial eruption following emotional stress and recent pregnancy. Examination reveals confluent inflammatory papules, pustules, large nodules, and draining sinus tracts strictly limited to the central face (cheeks, chin, forehead) with complete sparing of trunk and shoulders. Notably, there are NO comedones, seborrhea, or systemic symptoms. The structure marked **A** in the diagram shows central facial cysts and sinuses characteristic of this condition. Which of the following best describes the key distinguishing feature that differentiates the lesions marked **A** from cystic acne vulgaris?