Breast Inflammation: Mastitis, Periductal Mastitis & Duct...

Inflammatory Disorders of the Breast --- First, Why Does the Breast Get Inflamed? The breast is made of ducts, lobules, fat, and connective tissue. Inflammation can happen because of infection, blocked ducts, trauma, autoimmune reactions, or systemic diseases. Most of these conditions are benign but they matter because many of them mimic breast cancer — and that is the most important clinical point across almost all of them. --- 1. Acute Mastitis What is it? A bacterial infection of the breast tissue. Almost always happens during the first month of breastfeeding. Why does it happen during breastfeeding? Breastfeeding causes cracks and fissures in the nipple. These small breaks in the skin create an entry point for bacteria — mainly Staphylococcus aureus, and less commonly Streptococci. What happens? Initially only one duct or one sector of the breast is involved If untreated, it spreads to the whole breast Staph aureus → forms single or multiple abscesses — localized pockets of pus Streptococci → causes spreading cellulitis — diffuse infection through tissue without abscess formation Features: Breast is red, swollen, painful Fever is present Usually only one breast affected Treatment: Antibiotics Continue expressing milk — do not stop breastfeeding Surgical drainage only if abscess does not resolve with antibiotics --- 2. Squamous Metaplasia of Lactiferous Ducts Also known as: Recurrent subareolar abscess Periductal mastitis Zuska disease What is it? Normally, the nipple ducts are lined by glandular epithelium on the inside and squamous epithelium near the nipple opening. In this condition, the squamous epithelium grows too far inward — deeper into the duct than it should. This is called squamous metaplasia. Why does it happen? More than 90% of cases are in smokers Smoking causes vitamin A deficiency or direct toxic damage → this alters how ductal epithelial cells differentiate → they become squamous instead of glandular What happens next — step by step: Squamous cells grow deep into the duct Squamous cells shed keratin — dead skin flakes Keratin gets trapped and plugs the duct Blocked duct dilates and eventually ruptures Keratin spills into surrounding tissue The body reacts to keratin as a foreign substance → intense granulomatous inflammation develops around the spilled keratin In recurrent cases, secondary anaerobic bacterial infection joins in → acute inflammation on top of chronic inflammation Over time a fistula tract forms — a tunnel running under the nipple smooth muscle and opening onto skin at the edge of the areola The inflammation and scarring pull the nipple inward → nipple inversion Features: Painful red subareolar mass — looks exactly like a bacterial abscess Nipple inversion in chronic cases Fistula opening at the areola edge in recurrent cases Almost always in smokers Treatment: Simple incision drains the abscess but does not cure it — the abnormal squamous epithelium remains and the abscess comes back Definitive treatment: en bloc surgical removal of the involved duct and fistula tract Antibiotics if secondary bacterial infection is present --- 3. Duct Ectasia What is it? Ectasia means abnormal dilation. In duct ectasia, the large ducts near the areola become dilated and fill up with thick secretions. This is a degenerative condition, not an infection. Who gets it? Women in their fifth or sixth decade — older than those with squamous metaplasia Usually multiparous women — women who have had multiple pregnancies Not associated with smoking — unlike Zuska disease What happens — step by step: Ducts dilate and fill with thick, inspissated (dried-up, pasty) secretions Lipid-laden macrophages accumulate inside the dilated ducts — they are eating the secretion debris Eventually the duct wall ruptures Contents spill into surrounding tissue Chronic inflammatory reaction — lymphocytes, macrophages, plasma cells Granulomas form around cholesterol deposits from the spilled secretions Fibrosis follows → produces an irregular firm mass Fibrosis pulls on skin and nipple → skin retraction and nipple retraction Features: Palpable periareolar mass Thick white nipple discharge — very characteristic Skin or nipple retraction in later stages Pain and redness are uncommon — unlike mastitis Most important clinical point: Duct ectasia can be very difficult to distinguish from invasive carcinoma — both cause a hard periareolar mass and nipple retraction This is why it matters — you need to rule out cancer --- 4. Fat Necrosis What is it? Death of fat cells in the breast, usually following trauma or surgery. Dead fat cells trigger an inflammatory reaction that heals by scarring — and that scar can look and feel exactly like cancer. Who gets it? About half of patients have a history of breast trauma or prior surgery The other half have no obvious cause What happens — step by step: Fat cells are injured → central liquefactive necrosis forms Neutrophils and macrophages rush in to clean up — acute phase Within days, fi