Modified sweat gland, superficial fascia of pectoral region. Important for understanding signs/spread of carcinoma breast.

Structure (3 components)

Nipple — below breast centre, level 4th ICS, ~10 cm from midline; 15–20 lactiferous ducts pierce it; circular+longitudinal smooth muscle; no fat deep to nipple; rich sensory innervation (suckling reflex)

Areola — pigmented skin around nipple; modified sebaceous glands; darkens/enlarges in pregnancy; enlarged glands in pregnancy/lactation = Montgomery’s tubercles (lubricating secretion)

Stroma

Cooper’s ligaments — dermis to ducts/pectoral fascia; cancer infiltration shortens → skin dimpling/retraction

Parenchyma — compound tubuloalveolar gland

Myoepithelial cells around alveoli/ducts eject milk

Milk control: Prolactin (anterior pituitary) → secretion; Oxytocin (posterior pituitary) → ejection via myoepithelial contraction; suckling = neuroendocrine reflex trigger

Extent and Relations

Deep relations: pectoralis major, serratus anterior (inferolateral), external oblique (inferolateral)

• Separated from pectoral fascia by retromammary space (loose areolar tissue)

Allows normal mobility; surgical plane in simple mastectomy; carcinoma infiltration here + pectoral fascia → fixity to chest wall

Axillary tail of Spence — superolateral extension into axilla, through foramen of Langer; must be examined/removed in mastectomy; common carcinoma site (upper lateral quadrant)

Quadrants:

Blood Supply

Posterior surface relatively avascular — useful surgically

Venous Drainage

• Channels: internal thoracic veins, axillary vein, posterior intercostal veins, superficial lower neck veins
• Venous circle around nipple

Posterior intercostal veins communicate with vertebral venous plexus of Batson (valveless) → metastatic spread to vertebrae, spinal cord, skull, brain

Lymphatic Drainage (HIGH YIELD)

• Subareolar plexus of Sappey

Main drainage:

By region:

Axillary pathway: anterior axillary → central axillary → apical axillary → supraclavicular → subclavian lymph trunk

Upper lateral tumours → anterior axillary nodes first; medial tumours → internal mammary nodes ± opposite breast; superficial cross-communication → bilateral spread; lower medial → subperitoneal communication (secondary ovarian deposits described in exam anatomy)

Development

• From ectodermal mammary ridge (milk line), axilla to groin

Steps: mammary ridge (4th week) → persists only in pectoral region → ectodermal buds into mesenchyme → cords canalise → lactiferous ducts → 15–20 lobes → nipple eversion at birth

Anomalies:

Applied Anatomy

Carcinoma Breast

• Most common female malignancy; age 40–60+; origin: lactiferous duct epithelium; commonest site: upper lateral quadrant
• Lymphatic spread more important than blood spread early

Signs and Basis

Spread

Surgical incisions — made radially to avoid cutting across multiple ducts

Mastectomy types

Gynaecomastia — male breast enlargement, ↑oestrogen relative to androgen effect

• Associations: puberty, Klinefelter syndrome, liver cirrhosis, oestrogen-secreting tumours, drugs (spironolactone, cimetidine, digoxin, anabolic steroids)

The breast, or mammary gland, is a modified sweat gland situated in the superficial fascia of the pectoral region. In MBBS exams, the breast is important mainly because its structure, lymphatic drainage, and fascial relations explain the signs and spread of carcinoma breast.

Study it in this order:

1. Structure
2. Extent and relations
3. Blood supply and lymphatic drainage
4. Development
5. Applied anatomy

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Structure

The breast consists of three components:

Nipple

• Conical projection just below the centre of the breast
• Usually at the level of the 4th intercostal space, about 10 cm from the midline
• Pierced by 15-20 lactiferous ducts
• Contains circular and longitudinal smooth muscle fibres
• No fat lies deep to the nipple
• Rich in sensory nerve endings; important in the suckling reflex

Areola

• Pigmented skin around the nipple
• Contains modified sebaceous glands
• Darkens and enlarges during pregnancy
• Enlarged sebaceous glands in pregnancy and lactation form Montgomery’s tubercles
• Oily secretion lubricates the nipple and areola during lactation

Stroma

The stroma gives support and shape to the breast.

Suspensory ligaments of Cooper are fibrous septa that pass from the dermis to the ducts and pectoral fascia. They maintain the contour of the breast.

Clinical importance:

• Cancer infiltration shortens these ligaments.
• This causes skin dimpling or skin retraction.

Parenchyma

The mammary gland proper is a compound tubuloalveolar gland.

Myoepithelial cells around alveoli and small ducts help eject milk into the ducts.

Control of Milk Secretion

• Prolactin from the anterior pituitary stimulates milk secretion.
• Oxytocin from the posterior pituitary causes milk ejection by contraction of myoepithelial cells.
• Suckling stimulates the neuroendocrine reflex.

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Relations and Extent

Location

The breast lies in the superficial fascia of the pectoral region.

Extent

Deep Relations

The breast lies mainly on:

1. Pectoralis major
2. Serratus anterior, inferolaterally
3. External oblique, inferolaterally

It is separated from pectoral fascia by loose areolar tissue called the retromammary space.

Retromammary Space

Importance:

• Allows normal breast mobility over pectoralis major.
• Provides a surgical plane in simple mastectomy.
• If carcinoma infiltrates this space and pectoral fascia, the breast becomes fixed to the chest wall.

Axillary Tail of Spence

• Superolateral extension of breast tissue into the axilla
• Passes through the deep fascia through the foramen of Langer
• Must be examined clinically and removed during mastectomy
• Common site for carcinoma because much breast tissue lies in the upper lateral quadrant

Quadrants

The breast is divided into four quadrants by vertical and horizontal lines through the nipple.

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Blood Supply

The breast is highly vascular.

The posterior surface is relatively avascular, which is useful surgically.

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Venous Drainage

Venous drainage largely follows arterial supply.

Important channels:

• Internal thoracic veins
• Axillary vein
• Posterior intercostal veins
• Superficial veins of lower neck

Veins around the nipple form an anastomotic venous circle.

Clinical importance:

• Posterior intercostal veins communicate with the vertebral venous plexus of Batson.
• This valveless plexus allows metastatic spread to vertebrae, spinal cord, skull, and brain.

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Lymphatic Drainage

This is the most important exam section because carcinoma breast spreads mainly through lymphatics.

Superficial and Deep Lymphatics

The lymphatics beneath the areola form the subareolar plexus of Sappey.

Main Drainage

Drainage by Region

Axillary Pathway

Anterior axillary nodes
→ Central axillary nodes
→ Apical axillary nodes
→ Supraclavicular nodes
→ Subclavian lymph trunk

Clinical Importance

• Upper lateral quadrant tumours commonly spread first to anterior axillary nodes.
• Medial quadrant tumours may spread to internal mammary nodes and the opposite breast.
• Cross-communication of superficial lymphatics can cause bilateral involvement.
• Lower medial lymphatics may communicate with subperitoneal lymphatics; secondary ovarian deposits are described in exam anatomy, although Krukenberg tumour classically refers to metastatic ovarian tumour, commonly from the stomach.

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Development

The breast develops from the ectodermal mammary ridge or milk line, which extends from axilla to groin.

Steps

1. Mammary ridge appears in the 4th week.
2. It persists only in the pectoral region.
3. Ectodermal buds grow into underlying mesenchyme.
4. Solid cords canalise to form lactiferous ducts.
5. 15-20 lobes develop.
6. Nipple forms by eversion of the mammary pit at birth.

Developmental Anomalies

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Applied Anatomy

Carcinoma Breast

Important facts:

• Most common malignancy in females
• Common age group: 40-60 years and older
• Common origin: epithelium of lactiferous ducts
• Commonest site: upper lateral quadrant
• Lymphatic spread is more important than blood spread in early disease

Signs and Anatomical Basis

Spread of Carcinoma Breast

Surgical Incisions

Incisions in the breast are made radially to avoid cutting across multiple lactiferous ducts.

Mastectomy

Gynaecomastia

Gynaecomastia is enlargement of male breast tissue due to increased oestrogen effect relative to androgen effect.

Associations:

• Puberty
• Klinefelter syndrome
• Liver cirrhosis
• Oestrogen-secreting tumours
• Drugs such as spironolactone, cimetidine, digoxin, and anabolic steroids

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Rapid Revision Table

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