Breast abscess pathophysiology
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Following untreated mastitis, breast abscess could occur. Breast abscess is usually caused by staphylococcus aureus bacterial infection to an injured breast skin. Staphylococcus aureus could form abscess by secretion of several killing agents like enzymes and toxins which causes breast tissue necrosis. In a reaction to these bacterial substances, assembled white blood cells in this tissue produces anti-bacterial anti-bodies that help in killing the bacteria. However, these cells cause damage to the soft tissue contributing in the abscess formation. As the breast abscess is the complicated form of mastitis, the pathophysiology is mostly like the mastitis pathophysiology.
Breast abscess is the result of underlying inflammation (mastitis) in the breast skin. Injury may happen either during the lactation process from the infant or in the non-lactaion state of the patient as a cracking in the breast skin. This injury accelerates the entry of the causative bacteria which by its role form the abscess. 
In neglected cases, there may be necrosis in the abscess location leads to fibrosis, scarring and nipple retraction.
- Injured breast skin allows the entrance of the bacteria to the mammillary ducts. This bacteria can be from the infant or the mother herself. Overproduction of the breast milk with no flow to the infant forms an opportunistic field for the bacteria to cause infection.
- Breast Duct Ectasia: Metaplastic change of the duct cells can cause duct ectasia. This change causes widening of the ducts lining which leads to thickening of the ducts and obstruction. The ducts become filled with fluid which leads to nipple discharge and infection by the entrance of the bacteria and can form pus and abscess as a final result. 
The gross findings can be confused with other malignant diseases.
- Ill-defined with overlying skin thickening
- Nipple retraction
The following findings can be demonstrated on a pathology slide
- Lymphocytes along with neutrophils are gathered around the central abscess cavity filled with pus.
- Inflammatory infiltration involves gland buds and surrounding stroma along with lymphatic ducts.
- Foamy histiocytes are demonstrated in the dilated ducts.
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- Marchant DJ (2002). "Inflammation of the breast.". Obstet Gynecol Clin North Am. 29 (1): 89–102. PMID 11892876.
- Bundred NJ, Dixon JM, Lumsden AB, Radford D, Hood J, Miles RS; et al. (1985). "Are the lesions of duct ectasia sterile?". Br J Surg. 72 (10): 844–5. PMID 4041720.