Posterior extension of a breast abscess is most likely to produce which type of abscess?

• A. Subpectoral abscess
• B. Subscapular abscess
• C. Axillary abscess
• D. Mediastinal abscess

Answer: (A)

When a breast abscess extends posteriorly, it tends to track through the retromammary space and into the chest wall, landing in the space beneath the pectoralis major muscle. That area is the subpectoral compartment, so a posterior extension most naturally forms a subpectoral abscess. The other options are less likely because they involve spaces that are either farther from the breast tissue (such as behind the scapula) or in a lateral/medial direction (axillary or mediastinal) and do not align with the direct posterior path from the breast tissues.