Primary eruption was raised above the skin surface, up to 5 mm in diameter, formed as a result of changes in the dermis, often disintegrating and disappearing leaving a scar (e.g. tuberculosis). May be inflammatory. Clinically in acne, such lesions resemble cysts and may enlarge and contract over the course of weeks, but are not cystic.
Source: A. Kaszuba, Z. Adamski: “Lexicon of dermatology”; XNUMXst edition, Czelej Publishing House