Pathophysiology of Nipple Retraction and Skin Dimpling / Puckering

Anatomical Basis

Cutaway anatomy of the mature breast - note Cooper ligaments fusing with the overlying dermis (Sabiston Textbook of Surgery)

1. Nipple Retraction

A. Congenital Nipple Inversion

• During puberty, the major milk ducts normally elongate, pushing the nipple forward (telarche occurs ~1 year before menarche).
• If the ducts fail to elongate, the nipple does not protrude - this is true nipple inversion.
• It does not predispose to breast cancer.
• It can interfere with breastfeeding and predispose to infection from retained debris.

B. Acquired Nipple Retraction - the two key causes:

i. Periductal Mastitis / Duct Ectasia (most common cause of longstanding retraction)

1. Duct ectasia: Major milk ducts dilate (>3 mm on ultrasound) and fill with debris - an abnormal involutional process.
2. The stagnant secretions (containing chemically irritating fatty acids and lipoid material) leak through the thinned duct wall into the periductal tissue.
3. This triggers periductal inflammation - predominantly plasma cell infiltrate (hence the old name "plasma cell mastitis").
4. Repeated inflammatory episodes cause periductal fibrosis.
5. The fibrous scarring shortens and tethers the major ducts, pulling the nipple inward - producing retraction.
6. In periductal mastitis, the retraction pattern is characteristically transverse slit-like or "fish-mouth" in shape.

Figure 58.18(a) - Slit-like nipple retraction due to periductal mastitis (Bailey & Love's)

ii. Carcinoma

1. A malignant tumour invades and infiltrates the periductal stroma and major ducts.
2. The desmoplastic (fibrotic) reaction around the tumour shortens the duct system.
3. The ducts tether and shorten the nipple inward - circumferential retraction (in contrast to the slit-like pattern of periductal mastitis).
4. Recent-onset nipple retraction is always worrisome and must be assumed to indicate carcinoma until proven otherwise.

Key distinction: Slit-like retraction = periductal mastitis. Circumferential retraction = carcinoma.

• Bailey and Love's Short Practice of Surgery, 28th Ed., p. 945
• Schwartz's Principles of Surgery, 11th Ed., p. 579

2. Skin Dimpling / Puckering

Mechanism

1. A breast carcinoma invades the fibrous interlobular stroma.
2. This induces a desmoplastic response - reactive fibrosis in and around the tumour.
3. Cooper's ligaments, anchored to the dermis at one end and the deep fascia at the other, are caught up in this fibrous reaction.
4. The shortened/tethered ligaments pull the overlying skin inward toward the tumour mass, producing a focal depression or dimple in the skin surface.
5. The result is a visible puckering or dimpling over or near the tumour site.

• Sabiston Textbook of Surgery, p. 1369

3. Peau d'Orange (a Related Sign)

1. Tumour cells invade and obstruct the subdermal lymphatic channels of the breast, or obstruct axillary lymph nodes.
2. Lymphatic obstruction causes interstitial fluid accumulation (lymphoedema) in the dermis.
3. The skin swells uniformly, but the hair follicles and sweat gland openings remain tethered by Cooper's ligaments at the dermis.
4. These fixed points create characteristic small pits in the swollen skin, producing the "orange peel" texture.
5. It is a sign of locally advanced breast cancer (Stage IIIB in inflammatory breast carcinoma).

• Robbins & Kumar Basic Pathology, p. 80
• Bailey and Love's Short Practice of Surgery, 28th Ed., p. 954

Summary Table