Mastitis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Pathophysiology
Nonpuerperal mastitis: Aetiology and Pathogenesis
Most clinically significant cases present as inflammation of the ductal and lobular system (galactophoritis) and possibly the immediately surrounding tissue.
Secretory stasis is the cause of nonpuerperal mastitis in about 80% of cases (Lanyi 2003). The retained secretions can get infected or cause inflammation by causing mechanical damage or leaking the lactiferous ducts. Autoimmune reaction to the secretions may be also a factor.
Several mechanisms are discussed throughout literature that may cause or predispose this (Lanyi 2003, Peters & Schuth 1989, Goepel & Pahnke 1991, Krause et al 1994).
- Secretory disease or galactorrhea
- Changes in permeability of lactiferous ducts (retention syndrome)
- Blockage of lactiferous ducts, for example duct plugging caused by squamous metaplasia of lactiferous ducts
- Trauma, injury
- Mechanical irritation caused by retention syndrome or Fibrocystic Condition
- Infection
- Autoimmune reaction to luminal fluid
About 25% of patients may be hyperprolactinemic and significant coincidence with fibrocystic condition and thyroid anomalies has been documented (Peters & Schuth 1989, Goepel & Pahnke 1991). Up to 50% of patients experience transient hyperprolactinemia possibly caused by the inflammation or treatment and most had abnormally high Prolactin reserve (Goepel & Pahnke 1991).
Prolactin, IGF-1 and TSH are important sytemic factors in galactopoiesis, their significance in secretory disease is not documented but it has been asserted that the mechanisms of secretory disease and galactopoiesis are closely related (Lanyi 2003).
Permeability the of the alveolar and ductal epithelia is mostly controlled by tight junction regulation and is closely linked to galactopoiesis and possibly secretory disease. The tight junctions are regulated by a multitude of systemic (prolactin, progesterone, glucocorticoids) and local (intramammary pressure, TGF-beta, osmotic balance) factors (Nguyen & Neville 1998)
Tobacco smoking appears to be an important factor in the aetiology of squamous metaplasia of lactiferous ducts, around 90% of patients with this condition are smokers. Current smokers have the worst prognosis and highest rate of recurrent abscesses.
Acromegaly may present with symptoms of non-puerperal mastitis.
Diabetes and many conditions with suppressed immune system can cause various infections of the breast and mastitis. Such conditions often present with inflammation of peripheral tissue and exotic infections.
Nipple piercings pose a risk due to bacterial infection following the injury and hormonal stimulation by the piercing (Jacobs et al 2003, Modest & Fangman 2002, Demirtas et al 2003).
Terminology
Depending on appearance, symptoms, aetiological assumptions and histopathological findings a variety of terms has been used to describe mastitis and various related aspects.
- Galactopoiesis: milk production
- Secretory disease: aberrant secretory activity in the lobular and lactiferous duct system, believed to be the most frequent factor causing galactophoritis. The secretions may be milk like or apocrine luminal fluid.
- Retention syndrome (aka retention mastitis): accumulation of secretions in the ducts with mainly intraductal inflammation.
- Galactostasis: like retention syndrome where the secret is known to be milk.
- Galactophoritis: inflammation of the lobular and lactiferous duct system, mainly resulting from secretory disease and retention syndrome.
- Plasma cell mastitis: plasma cells from the intraductal inflammation infiltrate surrounding tissue.
- Duct ectasia: literally widening of lactiferous ducts - relatively common finding in breast exams, increase with age. Strongly correlated with cyclic and very strongly with noncyclic breast pain. Correlation with mastitis is of anecdotal quality and has been questioned by recent research.
- Duct ectasia syndrome: in older literature this was used as synonym for nonpuerperal mastitis with recurring breast abscess, nipple discharge and possibly associated fibrocystic condition with blue dome cysts. Recent research shows that duct ectasia is only very weakly correlated with mastitis symptomes (inflammation, breast abscess). The use of the terms Duct Ectasia and Duct Ectasia Syndrome is inconsistent throughout the literature.
- Squamous metaplasia of lactiferous ducts: cuboid cells in the epithelial lining of the lactiferous ducts transform (squamous metaplasia) to squamous epithelial cells. Present in many cases of subareolar abscesses.
- Subareolar abscess: abscess bellow or in close vicinity of the areola. Mostly resulting from galactophoritis.
- Retroareolar abscess: deeper (closer to chest) than the lobular ductal system and thus deeper than a subareolar abscess.
- Periductal inflammation (aka periductal mastitis): inflammation infiltrated tissue surrounding lactiferous ducts. Almost synonym for subaerolar abscess. May be just a different name for plasma cell mastitis.
- Fistula: fine channel draining an abscess cavity
- Zuska's disease: periareolar abscess associated with squamous metaplasia of lactiferous ducts. Some authors also associate this with nipple discharge.