A 50 years old lady came to the surgeon with the complaints of a firm, painless mass in the upper lateral quadrant of her right breast. On examination the nipple was found to be retracted. Axillary lymph nodes were also palpable and firm. She was diagnosed as a case of Breast cancer. 3 7 3 4 a. What are the structures lying deep to the breast? b. Describe the lymphatic dralnage of the breast. c. What causes the retractlon of nipple? d. What is the anatomical basis of peau d' orange? e. Explain the anatomical basis of spread of cancer to vertebrae

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lymphatic drainage of breast axillary nodes diagram

A three-dimensional (3D) volume-rendered CT lymphography image of the axillary region in a patient with breast cancer, demonstrating lymphatic drainage pathways and sentinel nodes. The image displays a skin-rendered surface with overlaid hyper-dense (white) structures representing contrast-enhanced lymphatic vessels and nodes. Two proximal sentinel lymph nodes are indicated by white arrows, appearing as small, ovoid, high-density structures connected by delicate, branching lymphatic channels. A third, more distal sentinel node is highlighted by a yellow arrow, located along a separate lymphatic tributary. The lymphatic flow originates from large, irregular high-density areas representing the intradermal contrast injection sites near the nipple-areolar complex. A metallic localizing marker is visible on the skin surface to facilitate surgical planning. This diagnostic imaging highlights the utility of CT lymphography in identifying multiple or widely distributed sentinel nodes that might be overlooked during conventional radioisotope or dye-only mapping due to spatial separation or signal interference from the primary injection site.

$This diagnostic image is a Magnetic Resonance Lymphangiography (MRL) scan demonstrating the axillary lymphatic system in a breast cancer context. The grayscale image shows anatomical structures of the breast and axilla with gadolinium-based contrast enhancement highlighting the lymphatic pathway. Two distinct levels of axillary lymph nodes are identified by markers: Level 1 lymph nodes are indicated by arrowheads, appearing as bright, rounded hyperintense structures clustered in the lower axilla. Level 3 lymph nodes, indicated by arrows, are situated more superiorly and medially (infraclavicular region) and also exhibit high signal intensity, though they appear slightly smaller in this view. The image illustrates the use of MRL for visualizing nodal anatomy and mapping the lymphatic drainage pathway. High signal intensity (bright white) indicates successful contrast uptake, while the surrounding darker gray areas represent soft tissue and fat with lower signal intensity. This modality is used in oncology to assess lymph node morphology and potential metastatic involvement by identifying enhancement defects or vessel dilation.$

This diagnostic image is a Magnetic Resonance Lymphangiography (MRL) scan demonstrating the axillary lymphatic system in a breast cancer context. The grayscale image shows anatomical structures of the breast and axilla with gadolinium-based contrast enhancement highlighting the lymphatic pathway. Two distinct levels of axillary lymph nodes are identified by markers: Level 1 lymph nodes are indicated by arrowheads, appearing as bright, rounded hyperintense structures clustered in the lower axilla. Level 3 lymph nodes, indicated by arrows, are situated more superiorly and medially (infraclavicular region) and also exhibit high signal intensity, though they appear slightly smaller in this view. The image illustrates the use of MRL for visualizing nodal anatomy and mapping the lymphatic drainage pathway. High signal intensity (bright white) indicates successful contrast uptake, while the surrounding darker gray areas represent soft tissue and fat with lower signal intensity. This modality is used in oncology to assess lymph node morphology and potential metastatic involvement by identifying enhancement defects or vessel dilation.

This composite educational graphic illustrates four distinct patterns of axillary lymphatic drainage from the breast to sentinel lymph nodes (SLNs), using Contrast-Enhanced Ultrasound (CEUS) imaging and corresponding anatomical diagrams. The visual material is divided into four sets (A–D), each featuring a split-screen ultrasound image (CEUS and B-mode) alongside a schematic illustration. The primary components described are Lymphatic Channels (LC) and Sentinel Lymph Nodes (SLN). The four patterns shown are: (A) a single LC draining to a single SLN; (B) multiple LCs converging into a single SLN; (C) a single LC branching to multiple SLNs; and (D) multiple LCs draining to multiple separate SLNs. In the CEUS images, the LCs and SLNs are identified by high echogenicity (bright contrast enhancement) indicated by red arrows, facilitating real-time visualization of the drainage pathway. This content is intended for surgical oncology and radiology education, specifically regarding preoperative sentinel lymph node biopsy (SLNB) mapping in breast cancer staging. It demonstrates how CEUS can be used to identify complex lymphatic anatomy that may impact surgical planning.

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Breast Cancer - Anatomy-Based Clinical Answers

a. Structures Lying Deep to the Breast

The breast lies in the superficial fascia of the anterior thoracic wall and is separated from the underlying deep fascia by the retromammary space - a layer of loose areolar connective tissue. From superficial to deep, the structures deep to the breast are:

Deep (pectoral) fascia - the investing fascia overlying the pectoralis major
Pectoralis major muscle - the primary muscle deep to the breast, spanning from ribs II to VI laterally
Pectoralis minor muscle - enclosed in the clavipectoral fascia, which extends laterally to fuse with the axillary fascia
Serratus anterior (inferolaterally)
External oblique (inferiorly, overlying ribs 6-7)
Ribs and intercostal muscles (underlying the inferior extent)

The retromammary space contains loose connective tissue and allows the breast some degree of mobility over underlying structures. The plane immediately deep to the breast is typically avascular, though tiny perforating vessels derived from the anterior intercostal vessels may be encountered here.

Sabiston Textbook of Surgery, 21st ed.

Breast anatomy showing retromammary space, deep fascia, and pectoralis major

b. Lymphatic Drainage of the Breast

Lymph from all parts of the breast (nipple, areola, lobules, and stroma) first drains into the subareolar lymphatic plexus (of Sappey), and then follows several routes:

Primary Route (75%) - Axillary Nodes

The majority of lymph drains to the axillary lymph nodes, initially into the external mammary (anterior/pectoral) nodes (Level I). From there it ascends to:

Level I (inferior to pectoralis minor): external mammary, lateral axillary, subscapular nodes
Level II (posterior to pectoralis minor): central, interpectoral (Rotter's) nodes
Level III (medial/superior to pectoralis minor): apical (subclavian) nodes --> subclavian trunk --> venous angle

Secondary Routes

Internal mammary (parasternal) nodes - particularly for medial quadrant tumors; via medial collecting route
Supraclavicular nodes - especially in advanced disease
Interpectoral (Rotter's) nodes - between pectoralis major and minor
Deltopectoral nodes - along the cephalic vein
Contralateral breast - cross-midline drainage
Abdominal lymphatics - via inferior phrenic nodes (rare; relevant for subdiaphragmatic spread)

There is considerable individual variation in these drainage patterns.

Fischer's Mastery of Surgery, 8th ed.

Lymphatic drainage of the breast showing axillary levels, subareolar plexus, and all drainage routes

c. What Causes Retraction of the Nipple?

Nipple retraction in breast cancer has a specific anatomical basis:

The breast is supported by fibrous bands called the suspensory ligaments of Cooper (Cooper's ligaments). These run between the deep fascia of the breast (over pectoralis major) and the dermis of the overlying skin, providing shape and structural support.
These ligaments also attach to and support the nipple-areolar complex.
When a carcinoma grows in the breast, it elicits a fibrotic (desmoplastic) reaction in the surrounding stroma.
The cancer infiltrates and shortens the Cooper's ligaments. Since these ligaments are anchored to both the deep fascia and the skin/nipple, their fibrotic shortening pulls the nipple inward, causing retraction.
In cancers of the retroareolar region, direct involvement of the lactiferous ducts by the tumor also contributes - ductal fibrosis shortens the ductal system and draws the nipple inward.

"Carcinoma of the breast creates tension on these ligaments, causing pitting of the skin." - Gray's Anatomy for Students

Sabiston Textbook of Surgery; Gray's Anatomy for Students

d. Anatomical Basis of Peau d'Orange

Peau d'orange (French: "orange peel") describes the characteristic dimpled, thickened skin appearance seen in advanced breast cancer.

Anatomical Explanation:

The skin of the breast contains numerous cutaneous lymphatic channels draining through the dermis and subdermal layers. These lymphatics normally drain freely into the axillary nodes.

In breast cancer:

Tumor cells block the subdermal lymphatics directly (lymphatic permeation) OR block the axillary lymph nodes, causing back-pressure in the cutaneous lymphatics.
This results in dermal lymphoedema - fluid accumulation in the dermis causes diffuse skin thickening and swelling.
The skin is tethered at multiple points to the underlying dermis by the hair follicles and sweat gland ducts, which pass through the oedematous skin. These tethering points cannot expand - they remain fixed while the surrounding skin swells.
The result is a skin surface that looks like an orange peel - generalised swelling with multiple small pits corresponding to the hair follicle orifices.

Additionally, subcutaneous lymphatic obstruction and tumor growth pull on Cooper's ligaments, further contributing to skin dimpling and tethering.

"Peau d'orange is a sign of locally advanced disease due to obstruction of cutaneous lymphatic drainage of the breast, by infiltration of either subdermal lymphatics or axillary lymph nodes by tumour cells." - Bailey and Love's Short Practice of Surgery, 28th ed.

Robbins & Kumar Basic Pathology; Bailey and Love's, 28th ed.; Gray's Anatomy for Students

e. Anatomical Basis of Spread of Cancer to Vertebrae

Breast cancer spreads to the vertebrae via two main routes:

1. Haematogenous Spread via Batson's Vertebral Venous Plexus (Primary Mechanism)

Batson's plexus is a network of valveless epidural veins running along the anterior epidural space of the vertebral column.
These veins communicate freely with the intercostal veins, internal thoracic veins, and the azygos system - all of which drain the breast region.
Because these veins have no valves, blood can flow in either direction depending on intrathoracic and intra-abdominal pressure changes (e.g. during coughing, straining, Valsalva).
Tumor emboli from the breast can therefore enter these veins and travel retrograde into the vertebral venous sinusoids, seeding the bone marrow of vertebral bodies.
This route bypasses the lungs entirely, explaining why some patients develop vertebral metastases without pulmonary metastases.

2. Arterial (Systemic) Route

Tumor cells enter the systemic circulation via the axillary or internal thoracic veins --> subclavian vein --> right heart --> pulmonary circulation.
After passing through the lungs, tumor emboli in the arterial circulation can reach the nutrient arteries of the vertebrae, particularly targeting the red bone marrow of the vertebral bodies.

Pattern of Vertebral Involvement

The thoracic vertebrae are most commonly involved in breast cancer (reflecting direct haematogenous spread via Batson's plexus from the thoracic intercostal veins).
The order of frequency of skeletal metastases is: lumbar vertebrae > neck of femur > thoracic vertebrae > ribs > skull.
Bone metastases from breast cancer are generally osteolytic (though osteosclerotic and mixed types also occur).
Extensive bone marrow replacement may cause a leukoerythroblastic anaemia.

"The propensity of solid tumors to metastasize to the vertebral column probably reflects the high proportion of bone marrow located in the axial skeleton... spread through Batson's plexus, a network of veins along the anterior epidural space." - Harrison's Principles of Internal Medicine, 22nd ed.

Bailey and Love's Short Practice of Surgery, 28th ed.; Harrison's Principles of Internal Medicine, 22nd ed.

Summary Table

Feature	Anatomical Basis
Nipple retraction	Fibrotic shortening of Cooper's ligaments by tumor desmoplasia
Peau d'orange	Dermal lymphoedema from blockage of subdermal lymphatics or axillary nodes; skin tethered at hair follicle orifices
Axillary node involvement	75% of breast lymph drains to axillary nodes via subareolar plexus
Vertebral spread	Batson's valveless vertebral venous plexus allows retrograde hematogenous seeding of vertebral bone marrow

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