Mastitis: Inflammatory Disorder of the Breast

by Richard Mitchell, MD, PhD

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    00:01 Okay, then let's talk about mastitis or breast inflammation.

    00:06 There are a variety of causes for breast inflammation, it can be infection, it can be non infectious inflammation, as we'll talk about, and it could be inflammation due to malignancy.

    00:16 I'm not going to talk about malignancy in this talk, but there is a whole separate session that we will have together in the breast pathology series of talks all about cancer.

    00:27 So in terms of causes for mastitis or breast inflammation, there can be lactational mastitis, clearly associated with breastfeeding.

    00:35 It is benign inflammation of the breast.

    00:38 It's associated with an ascending staphylococcal infection due to poor milk drainage.

    00:45 We'll come back to each of these in turn, but I just wanted to give you a kind of an overview.

    00:48 Fat necrosis can occur with trauma, blunt force injury, such as hitting a steering wheel, surgery, or radiation.

    00:59 Duct ectasia is somewhat idiopathic typically occurs in older individuals, but there's certain laxity of the fibrous connective tissue of the breast, and we get expansion that allows a retrograde ascending movement of bacteria so you can get then infection.

    01:18 Diabetic mastopathy is actually kind of an interesting entity, recognize only in the last decade or so.

    01:24 Occurs more frequently a type one versus type two diabetes that occurs with other endocrinopathies and may be an autoimmune manifestation.

    01:32 We'll come back to that.

    01:34 And then there's squamous metaplasia that like different stocks.

    01:37 This is associated with smoking in particular, and will occur with a metaplasia.

    01:44 So a change from the normal columnar or cuboidal epithelium lining the ducts to a more stratified squamous epithelium that will have kind of untoward manifestations that we'll see.

    01:58 That's the general scope of what we're going to be talking about when we talk about mastitis.

    02:03 Let's do some of the epidemiology.

    02:06 For lactational mastitis.

    02:07 This is clearly going to be involved with women who are breastfeeding and upwards of 10% of women who breastfeed can develop some degree of inflammation associated with it.

    02:19 Fat necrosis is overall a small fraction of the cases of mastitis and is again due to trauma, radiation, etc.

    02:30 Duct ectasia has an unknown incidence overall, it's usually perimenopausal, it's older women and is associated with laxity of the fibers connective tissue.

    02:43 Diabetic mastopathy is going to be upwards of 10 to 13% of women with type one diabetes much less if it's type two diabetes or in the general population.

    02:54 And squamous metaplasia, we really don't know the incidence overall.

    02:58 The pathophysiology, so we're gonna go through each of those forms and talk about how they happen.

    03:03 So for lactational mastitis, there's a poor milk drainage either due to a milk oversupply or infrequent feedings or duct blockage.

    03:14 The draining ducts will be in engorged and there may be micro organism overgrowth, so kind of an ascending infection.

    03:23 Typically, it's going to be a skin organism such as staphylococcus and then there will be secondary inflammation associated with that.

    03:33 With fat necrosis, clearly the pathogenesis is trauma or surgery.

    03:38 So in about 1% of breast reduction surgeries, for example, there will be some localized fat necrosis due to compromise of the vascular supply as they do the reduction mammoplasty.

    03:50 Duct ectasia is a non proliferative lesion.

    03:53 It's really loss of periductal elastic tissue.

    03:56 So the duct then gets kind of dilated and there is then retrograde or ascending bacterial infection.

    04:05 It may be a normal part of aging, and it can be certainly a cause of mastitis.

    04:11 And then there's the diabetic mastopathy.

    04:14 As I said before, it's autoimmune.

    04:16 It has an associated stromal fibrosis and lymphocytic vasculitis.

    04:20 The pathogenesis of squamous metaplasia involves the normal keratinizing squamous epithelium that sits over the surface of the skin and can extend to a very limited degree into the lactiferous ducts.

    04:35 With keratin sloughing from that keratinizing squamous epithelium, you may get focal duct obstruction.

    04:43 With duct obstruction, normally there is a movement of mucus and cells that have been slough from the epithelium that need to be released.

    04:53 If you block it with keratin then you can get a duct rupture because of the secondary expansion.

    04:59 And then with that duct rupture, you're going to extrude all that keratinaceous debris into the underlying tissue.

    05:07 With that, you will elicit inflammatory infiltrate, we can even get foreign body giant cells.

    05:13 Clinical features.

    05:14 So usually mastitis is unilateral.

    05:17 Clearly with breastfeeding and bilateral feeding, you may have a bilateral mastitis.

    05:24 Typically as it’s fluctuant, so somewhat squishy, tender mass, there will be associated edema, erythema and warmth and pain, especially with lactational mastitis during breastfeeding, as the milk is being expressed.

    05:39 Because this is inflammation, the draining lymph nodes will often become enlarged so you'll get a regional lymphadenopathy typically within the axilla, on the same side as the breast that is inflamed.

    05:50 And with more severe disease, you may experience signs of infection systemically such as fevers and rigors, fatigue, general malaise, etc.

    06:01 How are you going to make the diagnosis? Well, it's going to be physical exam, history, mammogram, and then you may want to proceed to ultrasound biopsy culture, the milk and blood culture depending on what you think.

    06:14 With ductal ectasia, we would see on mammogram or ultrasound, big dilated ducts often containing the normal secretory debris from normal glands within the breast.

    06:26 If there's fat necrosis, we may see elements of fat breakdown with associated a mononuclear cell infiltrate.

    06:34 And with diabetic mastopathy, we see a lot of fibrous stroma and an intervening mononuclear cell inflammatory infiltrate.

    06:44 Treatment.

    06:46 Mostly supportive, hot compresses and analgesics to hopefully - so the hot compresses will hopefully dilate the ducts and allow whatever is being retained.

    06:57 More proximately to be expressed, get out all of those secretions analgesics, obviously for pain.

    07:05 If infection is really indicated then antibiotics and surgical therapy, may be a last resort, especially for patients who have very dilated ectatic ducts that are recurrently becoming inflamed.

    07:21 With that we've covered the most important benign lesions associated with mastitis.

    About the Lecture

    The lecture Mastitis: Inflammatory Disorder of the Breast by Richard Mitchell, MD, PhD is from the course Breast Pathology.

    Included Quiz Questions

    1. Hard, irregular masses
    2. Soft, irregular masses
    3. Soft, regular masses
    4. Hard, regular masses
    1. 50 years old
    2. 30 years old
    3. 70 years old
    4. 80 years old
    5. 60 years old
    1. Duct blockage
    2. Milk oversupply
    3. Infrequent feedings
    4. Milk undersupply
    5. Frequent feedings
    1. Droplets of free fat of varying sizes
    2. Increase in the number of adipose cells
    3. Periductal fibrosis
    4. Microcalcifications
    5. Uniformly dilated ducts throughout the breast tissue

    Author of lecture Mastitis: Inflammatory Disorder of the Breast

     Richard Mitchell, MD, PhD

    Richard Mitchell, MD, PhD

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